#MPTP Inhibitors

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Mitochondrial Dysfunction in Cardiovascular Disease

 Introduction

Mitochondria are essential organelles responsible for the production of cellular energy in the form of adenosine triphosphate (ATP) through oxidative phosphorylation (OXPHOS). The heart, due to its continuous contractile activity, has a high energy demand and is critically dependent on mitochondrial function for normal physiological and pathological processes. Mitochondrial dysfunction has emerged as a central mechanism in the pathogenesis of cardiovascular diseases (CVDs), including ischemic heart disease, heart failure, hypertension, and arrhythmias. This technical overview discusses the molecular mechanisms of mitochondrial dysfunction in cardiovascular disease, its impact on cellular and organ function, and the potential therapeutic strategies to mitigate mitochondrial-related pathophysiology in CVDs.

Mitochondrial Function in Cardiovascular Cells

Mitochondria are highly dynamic organelles that perform several key functions crucial for the health of cardiovascular cells. They are involved in:

ATP Production via Oxidative Phosphorylation: In the mitochondria, energy production is driven by the electron transport chain (ETC), which is composed of complex I-IV embedded in the inner mitochondrial membrane. Electrons derived from NADH and FADH2 produced during the citric acid cycle are transferred through these complexes to ultimately reduce oxygen to water at complex IV. This electron transfer drives proton pumps that create an electrochemical gradient (proton motive force) across the inner mitochondrial membrane, which is utilized by ATP synthase (complex V) to produce ATP.

Calcium Homeostasis: Mitochondria play a crucial role in buffering intracellular calcium concentrations. They take up calcium from the cytoplasm in response to cellular signaling and help maintain cellular homeostasis by storing calcium in the matrix and releasing it when required for cellular signaling. Dysregulation of mitochondrial calcium handling can lead to pathophysiological conditions such as mitochondrial permeability transition (MPT) and cell death.

Reactive Oxygen Species (ROS) Production: Mitochondria are the primary source of ROS due to the incomplete reduction of oxygen molecules during electron transport in the ETC. Under normal conditions, low levels of ROS act as signaling molecules. However, excessive ROS generation due to mitochondrial dysfunction can cause oxidative stress, which damages cellular components such as lipids, proteins, and mitochondrial DNA (mtDNA), contributing to the pathogenesis of cardiovascular diseases.

Apoptosis and Cell Death: Mitochondria are central regulators of apoptosis. The release of pro-apoptotic factors such as cytochrome c from the mitochondrial intermembrane space into the cytoplasm triggers caspase activation, leading to programmed cell death. Mitochondrial dysfunction in cardiovascular tissues can lead to inappropriate cell death, contributing to the progression of CVDs.

Molecular Mechanisms of Mitochondrial Dysfunction in Cardiovascular Disease

Mitochondrial dysfunction in cardiovascular disease can result from several factors, including oxidative damage, altered mitochondrial dynamics, mutations in mitochondrial DNA, and defects in mitochondrial signaling. Below are the primary molecular mechanisms contributing to mitochondrial dysfunction in cardiovascular pathologies:

1. Oxidative Stress and ROS Accumulation

Excessive ROS generation is a hallmark of mitochondrial dysfunction and a major contributor to cardiovascular disease progression. Under normal conditions, the ETC produces ROS as a byproduct of electron transfer; however, under pathological conditions such as ischemia, hypoxia, or heart failure, there is an increase in mitochondrial ROS production. This increase is due to the altered electron flow through the ETC, particularly at complex I and III, which results in the incomplete reduction of oxygen.

The accumulation of ROS causes oxidative damage to mitochondrial lipids, proteins, and mtDNA. For instance, lipid peroxidation of mitochondrial membranes leads to membrane destabilization and disruption of mitochondrial function. ROS also modify proteins involved in mitochondrial dynamics and bioenergetics, impairing the capacity of mitochondria to generate ATP. Furthermore, oxidative damage to mtDNA leads to mutations that compromise the mitochondrial respiratory chain complexes, creating a vicious cycle of mitochondrial dysfunction.

2. Mitochondrial Permeability Transition (MPT) and Calcium Overload

Mitochondrial permeability transition is a critical event in mitochondrial dysfunction. The opening of the mitochondrial permeability transition pore (mPTP) occurs when the inner mitochondrial membrane becomes permeable to ions and small molecules, disrupting the electrochemical gradient required for ATP production. Under pathological conditions such as ischemia-reperfusion injury, excessive ROS and calcium overload activate the mPTP, leading to mitochondrial swelling, loss of membrane potential, and the release of pro-apoptotic factors (e.g., cytochrome c), triggering cell death.

Calcium overload plays a significant role in mitochondrial dysfunction. During stress conditions like ischemia, excessive intracellular calcium is taken up by mitochondria, causing mitochondrial matrix expansion and rupture of the mitochondrial membrane. This exacerbates cellular injury and promotes cell death pathways in the myocardium, contributing to myocardial infarction and heart failure.

3. Mitochondrial Dynamics Dysregulation

Mitochondrial dynamics refer to the continuous processes of mitochondrial fusion and fission that maintain mitochondrial quality and function. In response to cellular stress, mitochondria can undergo fission to segregate damaged components or fusion to promote functional compensation. Mitochondrial fission is regulated by dynamin-related protein 1 (DRP1), while fusion is mediated by mitofusins (MFN1 and MFN2) and optic atrophy 1 (OPA1). In cardiovascular diseases, this dynamic balance is often disrupted, leading to mitochondrial fragmentation, reduced mitochondrial function, and increased susceptibility to apoptosis.

In heart failure, for example, the upregulation of DRP1 and downregulation of fusion proteins contribute to mitochondrial fragmentation, reduced ATP production, and elevated ROS levels. This dysfunction is exacerbated by altered signaling pathways, including those associated with autophagy (mitophagy), which is responsible for removing damaged mitochondria. Dysfunctional mitophagy further impairs mitochondrial quality control, worsening cardiac injury.

4. Mitochondrial DNA Mutations

Mitochondrial DNA is more prone to mutations than nuclear DNA due to its proximity to the ETC and lack of protective histones. In cardiovascular diseases, mutations in mtDNA contribute to defective mitochondrial function. For example, mutations in genes encoding subunits of the OXPHOS complexes (such as ATP6, ND1, or CYTB) lead to impaired ATP synthesis and defective mitochondrial bioenergetics, contributing to myocardial ischemia and heart failure.

Mitochondrial mutations may also affect the regulation of ROS production and the activation of apoptotic pathways, accelerating tissue damage and organ dysfunction.

Therapeutic Approaches Targeting Mitochondrial Dysfunction in Cardiovascular Disease

Given the critical role of mitochondria in cardiovascular disease, several therapeutic strategies have been developed to target mitochondrial dysfunction and restore normal mitochondrial function. These include:

1. Mitochondrial Antioxidants

Mitochondrial-targeted antioxidants, such as MitoQ, MitoTEMPO, and SkQ1, have been developed to specifically target ROS within mitochondria. These compounds aim to reduce oxidative stress, limit mitochondrial damage, and improve mitochondrial function. Clinical studies are ongoing to assess the efficacy of these antioxidants in reducing myocardial injury and improving outcomes in heart failure and ischemic heart disease.

2. Mitochondrial Biogenesis Activation

Stimulating mitochondrial biogenesis to increase the number of functional mitochondria is another potential therapeutic strategy. Activators of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a key regulator of mitochondrial biogenesis, are being investigated as potential treatments for heart failure. Exercise training is a natural way to activate PGC-1α and increase mitochondrial function, which has been shown to improve cardiac outcomes in patients with heart failure.

3. MPTP Inhibition

Inhibitors of the mPTP, such as cyclosporine A, have been studied for their potential to prevent ischemia-reperfusion injury by inhibiting pore opening. By preserving mitochondrial integrity, these inhibitors may help reduce myocardial damage and improve survival after myocardial infarction.

4. Gene Therapy and Mitochondrial Transplantation

Gene therapy approaches, including the use of CRISPR/Cas9 to correct mitochondrial DNA mutations, hold promise in treating mitochondrial diseases. Additionally, mitochondrial transplantation, where healthy mitochondria are delivered to damaged cardiac cells, is an emerging area of research, with the potential to restore mitochondrial function and improve heart function in patients with severe myocardial injury.

Conclusion

Mitochondrial dysfunction plays a central role in the pathogenesis of cardiovascular diseases, contributing to impaired ATP production, increased ROS production, and cell death. Understanding the molecular mechanisms underlying mitochondrial dysfunction provides critical insights into the development of novel therapeutic strategies. Approaches targeting mitochondrial biogenesis, oxidative stress, mitochondrial dynamics, and mPTP inhibition offer promising avenues for the treatment of cardiovascular diseases and could lead to more effective management of conditions such as heart failure, ischemic heart disease, and hypertension. However, further research and clinical trials are needed to fully elucidate the potential of these therapeutic strategies in improving cardiovascular health.

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[CAUTION: This article is unusually complex. Life can be like that.]

There is growing interest in the nucleotide NAD+ (nicotinamide adenine dinucleotide) because of recent research revealing it’s regulation of diverse pathways controlling lifespan.1 A paper by Belensky et al2 in the same issue of Cell as a commentary on it1found that a precursor of NAD+ (nicotinamide riboside) extended yeast life span via activation of pathways that respond to increased NAD+, such as those that depend upon the SIR2 gene. Moreover, the beneficial effects of caloric restriction appear to be NAD+ dependent, as well as mediated by the NAD+-dependent SIRT1/Sir2 activity.3,4

The ratio of NAD+/NADH regulate many aspects of metabolism, including DNA repair, stress resistance, and cell death.4

“Changes in NAD+ metabolism have been associated with several pathologies, including neurodegenerative diseases, cancer, cardiovascular disease, and normal ageing.”4 In fact, the authors of paper #4 suggest that, “NAD+ synthesis through the kynurenine pathway [de novo synthesis of NAD+ from tryptophan] and/or salvage pathway [from nicotinamide] is an attractive target for therapeutic intervention in age-associated degenerative disorders.”

NAD+ is also reported to play a critical role as part of cellular respiration during the process of oxidative phosphorylation and ATP production.4 “Therefore, ATP synthesis and redox potential is directly proportional to intracellular NAD+ concentration.”4 The NAD+/NADH ratio is a measure of the metabolic state because of its importance in regulating intracellular redox state.4

Sirtuins are deacetylases that regulate large numbers of genes by removing acetyl groups from DNA. The function of the longevity gene SIRT1 has been shown to depend on the availability of NAD+. “Not surprisingly, the life-enhancing properties of sirtuins go hand in hand with those of NAD+ metabolism, suggesting a causal relationship where SIRT1 translates alterations of NAD+ levels into transcriptional events.”4 Interestingly, the DNA repair enzyme PARP (poly(ADP-ribose) polymerase) uses large amounts of intracellular NAD+ and is thereby in competition with sirtuins for the limited supply of NAD+. Under conditions of excessive expression of PARP, cellular NAD+ can be depleted, killing the cell. “Hyperactivation of PARP1 following DNA strand breaks can rapidly consume intracellular NAD+ pools, resulting in a loss of ability to synthesize ATP, and the cessation of all energy-dependent functions and consequent cell death.”4

The authors of paper #4 note that over-activation of PARP1 has been reported in the brains of Alzheimer’s disease patients, as well as in those with diabetes, MTPT-caused Parkinson’s disease, shock, and other conditions. It has been suggested that PARPs may play a role in aging by promoting NAD+ depletion. One study5 reported that PARP-1 activity in mononuclear blood cells increases with aging in at least thirteen mammalian species. In another study,5A researchers reported that “[o]ur results suggest that oxidative stress induced NAD+ depletion could play a significant role in the aging process, by compromising energy production, DNA repair and genomic surveillance.” The latter study5A examined the effect of aging on intracellular NAD+ metabolism in the whole heart, lung, liver and kidney of female Wistar rats, reporting that “[o]ur results are the first to show a significant decline in intracellular NAD+ levels and NAD/NADH ratio in all organs by middle age (i.e., 12 months) compared to young (i.e., 3 month old) rats … The strong positive correlation observed between DNA damage associated NAD+ depletion and Sirt1 activity suggests that adequate NAD+ concentrations may be an important longevity assurance factor.”

The authors of one paper5B write that “… when cells are subjected to oxidative stress by exposure to H2O2 [hydrogen peroxide], PARP-1 is activated and SIRT1 activity is robustly reduced, as PARP-1 activation limits NAD+ bioavailability. Treatment with PARP inhibitors in these circumstances allows the cell to maintain NAD+ levels and SIRT1 activity. … these observations indication that PARP-1 is a gatekeeper for SIRT1 activity by limiting NAD+ availability.”

The authors of paper #4 report that “[p]revious work from our group has shown for the first time that resveratrol induces a dose-dependent increase in activity of the NAD+ synthetic enzyme nicotinamide mononucleotide adenyl transferase (NMNAT1)” but that this is unpublished data.

Interestingly, a very recent paper found that “enhancement of the NAD+/NADH balance through treatment with NAD+ precursors inhibited metastasis in xenograft models [of breast cancer], increased animal survival, and strongly interfered with oncogene-driven breast cancer progression in the MMTV-PyMT mouse model.”6

Mitochondrial Biogenesis Induced by SirT1 Depends on Availability of NAD+

A very recent paper,6A in explaining how exercise or SirT1 activates PGC-1alpha, a master regulator of mitochondrial biogenesis, points out that the activity of SirT1 relies on NAD+ as a necessary coenzyme. The paper6A goes on to describe how, in its study of exercise in mice, chronic contractile activity (exercise) has a robust effect on mitochondrial biogenesis and that resveratrol acted synergistically with exercise to increase mitochondrial content when SirT1 was activated. “[T]he maximal effect of RSV [resveratrol] requires both SirT1 and a condition of energy demand in muscle that would be high in NAD+ and AMP, cofactors which activate SirT1 and AMPK, respectively.” 6A

Precursors That Can Be Taken As Supplements to Increase NAD+

There is (so far) remarkably little information on ways to increase NAD+ with natural products that are commercially available. There are three main physiological precursors: tryptophan, niacin, and niacinamide. It is reported that, “the administration of radiolabeled nicotinamide and nicotinic acid [niacin] has clearly shown that nicotinamide is a better precursor of NAD+ and that nicotinic acid is rapidly cleared by being converted to nicotinamide and excreted as nicotinuric acid.”6B Resveratrol was reported in paper #4 (but only as unpublished data) to dose-dependently increase the activity of the NAD+ synthetic enzyme nicotinamide mononucleotide adenyl transferase. In another paper,7 quercetin was reported to oxidize NADH to NAD+ in rat liver, thus increasing the availability of NAD+. However, as the researchers also explain, “direct measurements of NADH/NAD+ are very difficult to perform.”7 This was as of the paper’s publication in 2005. The researchers inferred the NADH/NAD+ ratio from the ratio of beta-hydroxybutyrate to acetoacetate. Quercetin has also been reported to be a PARP-1 inhibitor.7B Niacinamide is known to be an inhibitor of PARP, thus may prevent the decrease in NAD+ that results from PARP activity. There is a salvage pathway of specific enzymes that converts niacinamide to NAD+.

Niacinamide (NAM) As a PARP Inhibitor May Explain NAM’s Antiviral Effects

Interestingly, PARP is reported to be critical for the integration of foreign DNA, as absence of the PARP enzyme interrupts the HIV life cycle.7C An early study published in 1996 on the effects of niacin reported that a daily niacin (combining niacin and niacinamide) intake in AIDS patients that equaled only 3–4 times the U.S. recommended daily allowance (at that time) of 20 mg/day experienced slower progression and improved survival.7D That was, of course, well before the current multidrug cocktails were developed that enable HIV infected individuals to survive 20 years or more, but still demonstrates the anti-viral effects of the vitamin.

Other natural PARP inhibitors include the flavonoids fisetin and tricetin8 and flavone.9

More About PARP Inhibitors

Keep in mind that PARP is an important enzyme for DNA repair and transcription. Hence, PARP inhibition has to be limited so as to avoid excessive impairment of DNA repair. “Impaired SIRT1 activity due to PARP mediated NAD+ depletion allows increased activity of several apoptotic effectors such as p53, therefore sensitizing cells to apoptosis. Adequate NAD+ levels are therefore critical to maintaining Sirt1 activity which can delay apoptosis and provide vulnerable cells with additional time to repair even after repeated exposure to oxidative stress.”5A

PARP inhibitors are now being incorporated into therapy for diseases such as cancer and diabetes.10–12 This cripples the DNA repair ability of cancer cells, which generally have deficient DNA repair to start with, further limiting their ability to repair DNA and making the cancer cells more vulnerable to apoptosis. In diabetes, moderate PARP inhibition can help maintain cellular NAD+ availability for ATP synthesis. In fact, as mentioned above, overactivation of PARP1 has been reported in diabetes, Alzheimer’s disease, traumatic brain injury, shock, and other conditions.4 A recent paper5C reported that PARP is hyperactivated by oxidative stress induced by beta amyloid; this PARP overactivation (and depletion of NAD+) could be an important source of cell death in Alzheimer’s disease.

Another recent paper “provided quantitative evidence in support of the hypothesis that hyperactivation of PARP due to an accumulation of oxidative damage to DNA during aging may be responsible for increased NAD+ catabolism in human tissue. The resulting NAD+ depletion may play a major role in the aging process by limiting energy production, DNA repair and genomic signaling.”13 In this paper, the authors note that other investigators have linked PARP1 hyperactivity to diseases such as diabetes, MPTP-induced Parkinson’s disease and injury induced brain disorders. They further reported for the first time, in this study,13 that PARP activity increases with age in human skin, correlating with both age and NAD+ depletion (in males, but not in females). Consistent with the regulation of SIRT1 activity by NAD+ availability, they found a significant decline in SIRT1 activity with age in post-pubescent males but, again, not in females. The authors suggest that one possibility is that females have a greater capacity to recycle NAD+ from the PARP metabolite nicotinamide; however this remains to be determined.

References

1. Denu. Vitamins and aging: pathways to NAD+ synthesis. Cell. 1293):453-4 (May 4, 2007). 2. Belenky et al. Nicotinamide riboside promotes Sir2 silencing and extends lifespan via Nrk and Urh1/Pnp1/Meu1 pathways to NAD+. Cell. 129:473-84 (2007). 3. Wolf. Calorie restriction increases life span: a molecular mechanism. Nutr Rev. 64(2):89-92 (2006). 4. Massudi et al. NAD+ metabolism and oxidative stress: the golden nucleotide on a crown of thorns. Redox Rep. 17(1):28-47 (2012). 5. Grube and Burkle. Poly(ADP-ribose) polynerase activity in mononuclear cell lines of 13 mammalian species correlates with species specific lifespan. Proc Natl Acad Sci USA. 89:11759-63 (1992). 5A. Braidy et al. Age related changes in NAD+ metabolism oxidative stress and Sirt1 activity in Wistar rats. PLoS One. 6(4):e19194 (Apr. 2011). 5B. Canto and Auwerx. Interference between PARPs and SIRT1: a novel approach to healthy ageing? Aging. 3(5):543-7 (2011). 5C. Abeti and Duchen. Activation of PARP by oxidative stress induced by beta amyloid: implications for Alzheimer’s disease. Neurochem Res. 37:2589-96 (2012). 6. Santidrian et al. Mitochondrial complex I activity and NAD+/NADH balance regulate breast cancer progression. J Clin Invest. 123(3):1068-81 (2013). 6A. Menzies et al. Sirtuin 1-mediated effects of exercise and resveratrol on mitochondrial biogenesis. J Biol Chem. 288(10):6968-79 (2013). 6B. Imai. The NAD world: a new systemic regulatory network for metabolism and aging — Sirt1, systemic NAD biosynthesis, and their importance. Cell Biochem Biophys. 53:65-74 (2009). 7. Buss et al. The action of quercetin on the mitochondrial NADH to NAD+ ratio in the isolated perfused rat liver. Planta Med. 71:1118-22 (2005). 7B. Milo et al. Inhibition of carcinogen-induced cellular transformation of human fibroblasts by drugs that interact with the poly(ADP-ribose) polymerase system. FEBS J. 179(2):332-6 (1985). 7C. Murray. Nicotinamide: an oral antimicrobial agent with activity against both Mycobacterium tuberculosis and human immunodeficiency virus. Clin Infect Dis. 36:453-60 (2003) 7D. Tang et al. Effects of micronutrient intake on survival in human immunodeficiency virus type 1 infection. [a study of the Multicenter AIDS Cohort Study] Am J Epidemiol.143:1244-56 (1996) 8. Weseler et al. Poly (ADP-ribose) polymerase-1-inhibiting flavonoids attenuate cytokine release in blood from male patients with chronic obstructive disease or type 2 diabetes. J Nutr. 139:952-7 (2009). 9. Geraets et al. Flavone as PARP-1 inhibitor: its effect on lipopolysaccharide induced gene-expression. Eur J Pharmacol. 573:241-8 (2007). 10. Peralta-Leal et al. PARP inhibitors: new partners in the therapy of cancer and inflammatory diseases. Free Radic Biol Med. 47:13-26 (2009). 11. Soriano et al. Rapid reversal of the diabetic endothelial dysfunction by pharmacological inhibition of poly(ADP-ribose) polymerase. Circ Res. 89:684-91 (2001). 12. Du et al. Inhibition of GAPDH activity by poly(ADP-ribose) polymerase activates three major pathways of hyperglycemic damage in endothelial cells. J Clin Invest. 112(7):1049-57 (2003). 13. Massudi et al. Age-associated changes in oxidative stress and NAD+ metabolism in human tissue. PLoS One. 7(7):e42357 (July 2012).

[aleesblog]

Gerald Stern Journal of Neural Transmission supplement 2020

Gerald Stern was a doyen of clinical neurology of international repute who made numerous significant contributions to neurology and the field of movement disorders. His early life and career in neurology have been documented in other published eulogies (Lees 2018a, b; Quinn 2019; Lees and Ockelford 2019)—we would urge you to read these as they tell a compelling story of his upbringing, his entry in to medicine, and the start of his love affair with clinical neurology that contains object lessons for those about to embark on a similar voyage. For those of you who never met Gerald or heard him speak and have not read any of his numerous publications, you should indulge yourselves by reading one of his later works (Stern 2011) or the Stanley Fahn Lecture presented at the MDS meeting in 2010 in Bue- nos Aries which you can watch on YouTube (Stern 2010) and an interview carried out by Niall Quinn (Quinn 2010) following that presentation. Then, you will realise what a master of the English language he was, his intellect, his ability to dissect and analyse complex areas of neurology, and how he used his wit and humour to entertain an audience. Gerald showed boundless enthusiasm for clinical neurol- ogy and was beloved by his patients who adored the time and patience which he showed in trying to understand their problems and to treat them to the best of his ability. Such was the respect of his patients that two apparently penniless, little old ladies left him substantial legacies with which he funded his research. Famed for his tact and diplomacy and courteous manner, he was sought out by the rich, the famous, Kings, Presidents, and Popes for his clinical skills. Asked why he preferred to practice private medicine rather than aim for a chair of neurology, he responded in typical fashion ‘My dear boy, I couldn’t possibly afford to be a professor’. A pioneer and a non-conformist—some would say rebel—he was involved in the earliest studies of L-dopa in Parkinson’s disease and subsequently in the introduction of dopamine agonist drugs, notably apomorphine and bromocriptine. Probably, he would have been most proud of his contribution to the introduction of the MAO-B inhibitor deprenyl in to the treatment of Parkinson’s disease, which included being his own guinea pig for testing the safety and effect of the drug—unthinkable in the modern era. Less well known is Gerald’s love of science and laboratory-based research which was fostered by periods in his early career that he spent in USA and in Paris. He must have been one of very few clinicians who subscribed to and read Nature and Science on a regular basis. Enthused by articles that stimulated his imagination, he would be immediately on the telephone to discuss the details of the experiments or he would buttonhole people at meetings and have long conversations which showed the depth of his knowledge and his deep understanding of the relevance to clinical neurology. He would enthuse and even cajole his basic science colleagues in to action to exploit these latest ideas and to translate them in to practical solutions for his patient population. Gerald always described himself as ‘a simple clinician’, but those who worked with him found that he was far from that and including him in the basic science team raised novel ideas and concepts that his lateral thinking brought to the table.Gerald was involved in early studies on the function of the substantia nigra and sub-thalamic nucleus inducing electrolytic lesions in primates under the tutelage of Fred Mettler at Columbia University in New York. This formed the basis of his MD thesis which he wrote sitting on a bidet in a former bordello in Paris. He later forged long-term relationships with Professor Merton Sandler at Queen Charlottes Hospital, London studying catecholamine metabolism and, subsequently, the actions and metabolism of deprenyl. He then became fascinated by the potential for curing Parkinson’s disease through the use of foetal cell transplantation and in many respects was a pioneer in this field enabled by another long-term relationship with Professor Harry Bradford at Imperial College London. One of us (PJ) has personal experience of how Gerald never let an unsolved problem rest. One of his earliest studies, in 1963, was in to the cause of nigro-pallidal degeneration in horses induced by the ingestion of the yellow star thistle. Gerald tried unsuccessfully to induce the same degenerative process in both rodents and primates convinced that there was a specific toxin in the plant that had relevance to human disease. Some 30 years later, when MPTP was first coming to prominence, he related these studies to me, and after reading his paper, I was sufficiently convinced by Gerald’s enthusiasm to go back to the problem. Together with a Swiss phytochemist, toxic components of the plant extracts were identified as sesquiterpene lactones (Cheng et al. 1992)—although it still remains a mystery as to why only horses are affected. In his professional life, Gerald Stern was, by nature, a quiet, generous, and unselfish man who gave his time freely to others and was never one to seek the limelight. In fact, many will remember him because of the patronage which he showed to young neurologists and scientists encouraging them to greater things through his enthusiasm for the field. A gift that is not as common today and for which we are poorer. One of us (PJ) will be forever grateful for the support and encouragement that he received from Gerald in the early part of his career—everything from listening my woes to constructive criticism of my work to bombarding me with ideas to ensuring that I took the right path to achieve my ambitions. He was a father figure to many, but never took the credit for doing so much to advance the field of movement disorders in the UK and on an international basis. Perhaps,in these young people, he recognised something of himself and saw their struggles as the ones which he himself had had to overcome. One or two final quotations personify Gerald and his personality. ‘Surround yourself with clever young people who are more industrious, more imaginative, more intelligent than yourself’ and ‘Be nice to old ladies’. Rest in peace dear friend! References Cheng CH, Costall B, Hamburger M, Hostettmann K, Naylor RJ, Wang Y, Jenner P (1992) Toxic effects of solstitialin A 13-acetate and cynaropicrin from Centaurea solstitialis L. (Asteraceae) in cell cultures of foetal rat brain. Neuropharmacology 31:271–277 Lees AJ (2018a) In memoriam: Gerald Malcom Stern (October 9, 1930–September 9, 2018). Mov Disord 33:1831–1833 Lees, AJ (2018b) Munk’s Roll vol. XII, Royal College of Physicians, London. https://history.rcplondon.ac.uk/inspiring-physicians/geral d-malcolm-stern. Accessed Feb 2020 Lees AJ, Ockelford J (eds) (2019) Remembering Gerald Stern. Virginia Keiley Benefaction, London Quinn N (2010) Interview with Gerald Stern, Buenos Aries, MDS Archives. https://www.youtube.com/watch?v=EST-Otslc8g. Accessed Feb 2020 Quinn N (2019) Gerald Malcolm Stern: 9th October 1930–9th Septem- ber 2018. Mov Disord Clin Pract 6:9–10 Stern G (2010) Stanley Fahn Lecture, MDS Meeting, Buenos Aries. https://www.youtube.com/watch?v=q0_MZWVK3mE. Accessed Feb 2020 Stern G (2011) Why catechol? Mov Disord 26:24–26 Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

[healthtimetaylor]

Astaxanthin might be a potential effective therapeutic agent for Parkinson's disease.

PMID:  Neurosci Res. 2020 Apr 22. Epub 2020 Apr 22. PMID: 32333925 Abstract Title:  Astaxanthin suppresses endoplasmic reticulum stress and protects against neuron damage in Parkinson's disease by regulating miR-7/SNCA axis. Abstract:  Parkinson's disease (PD) is a common neurodegenerative disorder that featured by the loss of dopaminergic neurons. Astaxanthin (AST), an important antioxidant, is demonstrated to be a neuroprotective agent for PD. However, the underlying mechanisms of AST in PD remain largely unclear. In this study, we found that AST treatment significantly not only abolished the cell viability inhibition and apoptosis promotion induced by 1-methyl-4-phenylpyridinium (MPP+) in SH-SY5Y cells via inhibiting endoplasmic reticulum (ER) stress, but also reversed the MPP + caused dysregulation of miR-7 and SNCA expression. MiR-7 knockdown and SNCA overexpression were achieved by treating SH-SY5Y cells with miR-7 inhibitor and pcDNA3.1-SNCA plasmids, respectively. MiR-7 could bind to and negatively regulate SNCA in SH-SY5Y cells. Treated SH-SY5Y cells with miR-7inhibitor or pcDNA3.1-SNCA abrogated the protective effects of AST on MPP + induced cytotoxicity. Knockdown of miR-7 aggravated 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced neuron injury in vivo suggested by athletic performance, histopathological morphology, expression of tyrosine hydroxylase (TH) and TUNEL positvie cells, however, AST treatment could reverse these effects of miR-7 knockdown. Collectively, AST suppressed ER stress and protected against PD-caused neuron damage by targeting miR-7/SNCA axis, implying that AST might be a potential effective therapeutic agent for PD.

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[neurogenpapers]

NADPH oxidase-derived H2O2 mediates the regulatory effects of microglia on astrogliosis in experimental models of Parkinson's disease.

PubMed: NADPH oxidase-derived H2O2 mediates the regulatory effects of microglia on astrogliosis in experimental models of Parkinson's disease. Redox Biol. 2017 Feb 22;12:162-170 Authors: Hou L, Zhou X, Zhang C, Wang K, Liu X, Che Y, Sun F, Li H, Wang Q, Zhang D, Hong JS Abstract Astrogliosis has long been recognized in Parkinson's disease (PD), the most common neurodegenerative movement disorder. However, the mechanisms of how astroglia become activated remain unclear. Reciprocal interactions between microglia and astroglia play a pivotal role in regulating the activities of astroglia. The purpose of this study is to investigate the mechanism by which microglia regulate astrogliosis by using lipopolysaccharide (LPS) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse PD models. We found that the activation of microglia preceded astroglia in the substantia nigra of mice treated with either LPS or MPTP. Furthermore, suppression of microglial activation by pharmacological inhibition or genetic deletion of NADPH oxidase (NOX2) in mice attenuated astrogliosis. The important role of NOX2 in microglial regulation of astrogliosis was further mirrored in a mixed-glia culture system. Mechanistically, H2O2, a product of microglial NOX2 activation, serves as a direct signal to regulate astrogliosis. Astrogliosis was induced by H2O2 through a process in which extracellularly generated H2O2 diffused into the cytoplasm and subsequently stimulated activation of transcription factors, STAT1 and STAT3. STAT1/3 activation regulated the immunological functions of H2O2-induced astrogliosis since AG490, an inhibitor of STAT1/3, attenuated the gene expressions of both proinflammatory and neurotrophic factors in H2O2-treated astrocyte. Our findings indicate that microglial NOX2-generated H2O2 is able to regulate the immunological functions of astroglia via a STAT1/3-dependent manner, providing additional evidence for the immune pathogenesis and therapeutic studies of PD. PMID: 28237879 [PubMed - as supplied by publisher] http://dlvr.it/NV5X8p