Impact of exercise on mitochondrial transcription factor expression and damage in the striatum of a chronic mouse model of Parkinson's disease

Association of Diet and Physical Activity With All-Cause Mortality Among Adults With Parkinson Disease

IMPORTANCE

Greater diet quality and physical activity level are associated with a lower risk of developing Parkinson disease (PD). However, information regarding the association between lifestyle behaviors and survival after PD diagnosis remains limited.

OBJECTIVE

To examine the association of prediagnosis and postdiagnosis overall diet quality and physical activity with all-cause mortality among individuals with PD.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study analyzed male participants in the Health Professionals Follow-up Study from 1986 to 2012 and female participants in the Nurses' Health Study from 1984 to 2012. Participants who were diagnosed with PD and had complete baseline dietary assessment data were included. Data were analyzed from January 2021 to February 2022.

EXPOSURES

Prediagnosis diet quality, assessed by the Alternative Healthy Eating Index (AHEI), and physical activity, assessed by metabolic equivalent task (MET) hours per week reported on questionnaires, were the primary exposures of interest to minimize reverse causation.

MAIN OUTCOMES AND MEASURES

Mortality, which was followed up until 2018, was the primary outcome. Cox proportional hazards regression models were used to estimate the association of diet and physical activity with mortality individually and jointly, and the models were adjusted for age, total energy intake, caffeine intake, and other lifestyle risk factors.

RESULTS

The sample comprised 1251 individuals with PD, which included 652 men (52.1%) with a median (IQR) age at diagnosis of 73.4 (67.5-78.7) years. During the 32 to 34 years of follow-up, 942 participants died. The adjusted hazard ratio (HR) comparing the highest vs the lowest AHEI quartile was 0.69 (95% CI, 0.56- 0.85) for prediagnosis analyses and 0.57 (95% CI, 0.42-0.78) for postdiagnosis analyses. Similar results were obtained for cumulative mean MET hours per week in the prediagnosis analyses (HR, 0.71; 95% CI, 0.57-0.87) and postdiagnosis analyses (HR, 0.47; 95% CI, 0.35-0.63). The inverse association persisted for PD-specific mortality (postdiagnosis AHEI: HR, 0.52 [95% CI, 0.33-0.80]; postdiagnosis physical activity: HR, 0.37 [95% CI, 0.25-0.55]). In the joint analyses of diet quality and physical activity before the PD diagnosis, the adjusted HR was 0.51 (95% CI, 0.36-0.73) for individuals in the highest vs lowest tertiles for both variables. The HR for diet quality and physical activity after the diagnosis was 0.35 (95% CI, 0.23-0.52).

CONCLUSIONS AND RELEVANCE

Results of this study showed that a healthy dietary pattern and an active lifestyle were associated with a lower rate of all-cause mortality among individuals with PD. Consuming a healthy diet and engaging in physical activity or exercise could be targeted to improve PD outcomes.

Association of Physical Activity, Including Amount and Maintenance, With All-Cause Mortality in Parkinson Disease

Importance

The protective effects of physical activity (PA) against Parkinson disease (PD) development have been suggested; however, the association of PA with mortality in PD has rarely been investigated.

Objective

To evaluate the association between PA and mortality in individuals with PD and determine how the amount and maintenance of PA are associated with mortality.

Design, Setting, and Participants

This nationwide population-based cohort study used Korean National Health Insurance System data. Participants were included from January 1, 2010, and December 31, 2013, and were followed up until December 31, 2017. Data were analyzed from September 2020 to March 2021. Individuals who were newly diagnosed with PD were selected using the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision code G20 and registration code V124 in the program for rare intractable diseases in 2010 through 2013. Individuals who underwent health checkups within 2 years before and after the PD diagnosis were enrolled. Those aged younger than 40 years or with missing data were excluded.

Exposures

Physical activity levels were collected using self-reported questionnaires.

Main Outcomes and Measures

All-cause mortality.

Results

A total of 45 923 individuals were identified; 10 987 were enrolled, and 34 individuals younger than 40 years and 254 with missing data were excluded. A total of 10 699 individuals with PD were included; 4925 (46%) were male and 5774 (54%) were female, and the mean (SD) age was 69.2 (8.8) years. During the 8-year follow-up period, there were 1823 deaths (17%). The mortality rate was lower among individuals who were physically active vs inactive at all PA intensities (vigorous: hazard ratio [HR], 0.80 [95% CI, 0.69-0.93]; moderate: HR, 0.66 [95% CI, 0.55-0.78]; light: HR, 0.81 [95% CI, 0.73-0.90]). There was a significant inverse dose-response association between the total amount of PA and mortality (HRs: vigorous, 0.80 [95% CI, 0.69-0.93]; moderate, 0.66 [95% CI, 0.55-0.78]; light, 0.81 [95% CI, 0.73-0.90]; P < .001). Moreover, maintenance of PA was associated with the mortality rate. Individuals with PD who were physically active both before and after the PD diagnosis had the greatest reduction in mortality rate across all PA intensities (HRs: vigorous, 0.66 [95% CI, 0.50-0.88]; moderate, 0.49 [95% CI, 0.32-0.75]; light, 0.76 [95% CI, 0.66-0.89]). Individuals who started PA after receiving the PD diagnosis had a lower mortality rate than those who remained physically inactive (HRs: vigorous, 0.82 [95% CI, 0.70-0.97]; moderate, 0.69 [95% CI, 0.57-0.83]; light, 0.86 [95% CI, 0.78-0.98]).

Conclusions and Relevance

This analysis found a dose-response association between PA and all-cause mortality in PD. Reverse causality may exist, and future prospective randomized clinical trials are warranted to determine the effect of PA on mortality in PD.

The effects of treadmill exercise in animal models of Parkinson's disease: A systematic review

Parkinson's disease (PD) is a progressive disabling brain disorder. Physical exercise has been shown to alleviate the symptoms of PD and, consequently, improve patient quality of life. Exercise mechanisms involved in beneficial effects on PD have been widely investigated. This study aims to systematically review the literature on the use of treadmill exercise in PD animal models. The study was conducted according to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA). Searches were conducted in MEDLINE, EMBASE, and ISI databases. In total, 78 studies were included. The dopaminergic system, behavior, neuroplasticity, neuroinflammation, mitochondria, and musculoskeletal systems were some of the outcomes evaluated by the selected studies. Based on the systematic review center for laboratory animal experimentation (SYRCLE) RoB tool, the methodologies revealed a high risk of bias and lack of information about study design, which needs attention for data reproducibility. This review can guide future studies that aim to fill existing gaps regarding the effects of treadmill exercise in PD animal models.

Effects of Treadmill Exercise on Neural Mitochondrial Functions in Parkinson's Disease: A Systematic Review of Animal Studies

This systematic review sought to determine the effects of treadmill exercise on the neural mitochondrial respiratory deficiency and neural mitochondrial quality-control dysregulation in Parkinson's disease. PubMed, Web of Science, and EMBASE databases were searched through March 2020. The English-published animal studies that mentioned the effects of treadmill exercise on neural mitochondria in Parkinson's disease were included. The CAMARADES checklist was used to assess the methodological quality of the studies. Ten controlled trials were included (median CAMARADES score = 5.7/10) with various treadmill exercise durations (1-18 weeks). Seven studies analyzed the neural mitochondrial respiration, showing that treadmill training attenuated complex I deficits, cytochrome c release, ATP depletion, and complexes II-V abnormalities in Parkinson's disease. Nine studies analyzed the neural mitochondrial quality-control, reporting that treadmill exercise improved mitochondrial biogenesis, mitochondrial fusion, and mitophagy in Parkinson's disease. The review findings supported the hypothesis that treadmill training could attenuate both neural mitochondrial respiratory deficiency and neural mitochondrial quality-control dysregulation in Parkinson's disease, suggesting that treadmill training might slow down the progression of Parkinson's disease.

MiR-193b deregulation is associated with Parkinson's disease

PGC-1α/FNDC5/BDNF has found to be a critical pathway in neurodegeneration. MicroRNAs (miR(NA)s) are non-coding regulatory RNAs whose dysregulation has been observed in multiple neurological disorders, and miRNA-mediated gene deregulation plays a decisive role in PD. Here, candidate miRNA was chosen based on the literature survey and in silico studies. Chronic and acute models of PD were created using MPP+-treated SH-SY5Y cells. Twenty PD patients and 20 healthy volunteers were recruited. RT-qPCR was performed to assess the expression of miRNA and genes. Severe mitochondrial dysfunction induced by acute MPP+ treatment instigated compensatory mechanisms through enhancing expression of PGC-1α/FNDC5/BDNF pathway genes, while chronic MPP+ toxicity led to down-regulated levels of the genes in SH-SY5Y cells. PD peripheral blood mononuclear cells (PBMCs) also showed decreased expression of target genes. There were significant changes in the level of miR-193b in both models, as well as PD PBMCs. Moreover, miR-193b overexpression significantly affected PGC-1α, FNDC5 and TFAM levels. Interestingly, down-regulations of PGC-1α, FNDC5, BDNF and TFAM were inversely correlated with miR-193b up-regulation in PD PBMCs. This study showed the deregulation of PGC-1α/FNDC5/BDNF pathway in PD models and PBMCs, verifying its importance in neurodegeneration. Our findings also revealed that miR-193b functions in PD development, possibly through regulating PGC-1α/FNDC5/BDNF pathway, suggesting miR-193b as a potential biomarker for PD diagnosis.

Exercise-Induced Neuroprotection in the 6-Hydroxydopamine Parkinson's Disease Model

Exercise exerts helpful effects in Parkinson's disease. In this study, the 6-hydroxydopamine (6-OHDA) injection was used to investigate the effect of exercise on apomorphine-induced rotation and neurorestoration. Rats (n = 32) were divided into four groups: (1) Saline+Noexercise (Sham); (2) 6-OHDA+Noexercise (6-OHDA); (3) Saline+Exercise (S+EXE), and (4) 6-OHDA+Exercise (6-OHDA+EXE). The rats were administered 8 μg 6-OHDA by injection into the right medial forebrain bundle. After 2 weeks, the exercise group was run (14 consecutive days, 30 min per day). One month after the surgery, following the injection of apomorphine, the 6-OHDA group displayed a significant increase in rotation and the 6-OHDA+EXE group showed a significant reduction of rotational asymmetry (P < 0.001). 6-OHDA injection reduced the mRNA and protein expression of the AMP-activated protein kinase, brain-derived neurotropic factor, and tyrosine hydroxylase in relation to the Sham group and exercise increased these levels. Expression of the silent information regulator 2 homolog 1 and peroxisome proliferator-activated receptor gamma coactivator 1-alpha was unexpectedly enhanced in the 6-OHDA groups in relation to the Sham group. These findings suggest that the 6-OHDA injection increased the neurodegeneration and mitochondrial and behavioral dysfunctions and the treadmill running attenuated these disorders in the ipsilateral striatum of the 6-OHDA+EXE group.

Exercise effects on brain and behavior in healthy mice, Alzheimer's disease and Parkinson's disease model-A systematic review and meta-analysis

This systematic review and meta-analysis examines how exercise modifies brain and behavior in healthy mice, dementia (D) and Parkinson disease (PD) models. A search was performed on the Medline and Scopus electronic databases (2008-2019). Search terms were "mice", "brain", "treadmill", "exercise", "physical exercise". In the total, 430 were found but only 103 were included. Animals n = 1,172; exercised 4-8 weeks (Range 24 h to 32 weeks), 60 min/day (Range 8-120 min per day), and 10/12 m/min (Range 0.2 m/min to 36 m/min). Hippocampus, cerebral cortex, striatum and whole brain were more frequently investigated. Exercise improved learning and memory. Meta-analysis showed that exercise increased: cerebral BDNF in health (n = 150; z = 5.8, CI 3.43-12.05; p < 0.001 I2 = 94.3 %), D (n = 124; z = 4.18, CI = 2.22-9.12; p < 0.001; I2 = 93.7 %) and PD (n = 16 z = 4.26, CI 5.03-48.73 p < 0.001 I2 = 94.8 %). TrkB improved in health (n = 84 z = 5.49, CI 3.8-17.73 p < 0.001, I2 = 0.000) and PD (n = 22; z = 3.1, CI = 2.58-67.3, p < 0.002 I2 = 93.8 %). Neurogenesis increased in health (n = 68; z = 7.08, CI 5.65-21.25 p < 0.001; I2 17.58) and D model (n = 116; z = 4.18, CI 2.22-9.12 p < 0.001 I2 93.7 %). Exercise augmented amyloid clearance (n = 166; z = 7.51 CI = 4.86-14.85, p < 0.001 I2 = 58.72) and reduced amyloid plaques in D models (n = 49; z = 4.65, CI = 3.94-15.3 p < 0.001 I2 = 0.000). In conclusion, exercise improved brain and behavior, neurogenesis in healthy and dementia models, reduced toxicity and cerebral amyloid. Evidence regarding inflammation, oxidative stress and energy metabolism were scarce. Studies examining acute vs chronic exercise, extreme training and the durability of exercise benefit were rare. Vascular or glucose metabolism changes were seldom reported.

The effect of preventive exercise on the neuroprotection in 6-hydroxydopamine-lesioned rat brain

Parkinson's disease is characterized by neurodegeneration and learning deficiency. Physical exercise can alleviate these symptoms by increasing the expression of some effective and relevant factors. The preventive effect of 16-week treadmill running in a rat model of Parkinson's disease, before 6-hydroxydopamine (6-OHDA) induction, was assessed. Experimental groups consisted of sedentary (SED), SED+6-OHDA, exercised (EX), and EX+6-OHDA rats. Forty-eight hours after the last session of exercise, 6-OHDA was injected into the medial forebrain bundle (MFB). One week after the injection, behavioral tests, including spatial learning and memory, were assessed through Morris water maze (MWM) and apomorphine-induced rotation. Three weeks after the injection, mRNA expression and protein levels of the transcriptional co-activator peroxisome-proliferator-activated receptor-γ co-activator-1α (PGC-1α), fibronectin type III domain-containing protein 5 (FNDC5), brain-derived neurotrophic factor (BDNF), and tyrosine hydroxylase (TH) were measured in the striatum and the hippocampus of rats by applying real-time PCR and Western blotting. The findings indicate that exposure to 6-OHDA leads to impairments in behavioral and molecular functions. Exercise training prevents and reduces the symptoms caused by dopamine toxins. The results suggest that treadmill running can exert neuroprotective and have preventive effects to reduce Parkinson's disease symptoms. Novelty Parkinson's disease impairs spatial learning and memory. Parkinson's disease reduced levels of PGC-1α, FNDC5, and BDNF and increased neurodegeneration in the striatum and the hippocampus. Treadmill running before disease attenuated 6-OHDA-induced memory deficit and elevated neuroprotection. Exercise has multiple effects on memory and biochemical factors.

Exercise-Induced Neuroprotection and Recovery of Motor Function in Animal Models of Parkinson's Disease

Parkinson's disease (PD) is manifested by progressive motor, autonomic, and cognitive disturbances. Dopamine (DA) synthesizing neurons in the substantia nigra (SN) degenerate, causing a decline in DA level in the striatum that leads to the characteristic movement disorders. A disease-modifying therapy to arrest PD progression remains unattainable with current pharmacotherapies, most of which cause severe side effects and lose their efficacy with time. For this reason, there is a need to seek new therapies supporting the pharmacological treatment of PD. Motor therapy is recommended for pharmacologically treated PD patients as it alleviates the symptoms. Molecular mechanisms behind the beneficial effects of motor therapy are unknown, nor is it known whether such therapy may be neuroprotective in PD patients. Due to obvious limitations, human studies are unlikely to answer these questions; therefore, the use of animal models of PD seems indispensable. Motor therapy in animal models of PD characterized by the loss of dopaminergic neurons has neuroprotective and neuroregenerative effects, and the completeness of neuronal protection may depend on (i) degree of neuronal loss, (ii) duration and intensity of exercise, and (iii) time elapsed between insult and commencing of training. As the physical activity is neuroprotective for dopaminergic neurons, the question arises what is the mechanism of this protective action. A current hypothesis assumes a central role of neurotrophic factors in the neuroprotection of dopaminergic neurons, even though it is still not clear whether increased DA level in the nigrostriatal axis results from neurogenesis of dopaminergic neurons in the SN, recovery of the phenotype of dopaminergic neurons, increased sprouting of the residual dopaminergic axons in the striatum, or generation of local striatal neurons from inhibitory interneurons. In the present review, we discuss studies describing the influence of physical exercise on the PD-like changes manifested in animal models of the disease and focus our interest on the current state of knowledge on the mechanism of neuroprotection induced by physical activity as a supportive therapy in PD.

Exercise and Parkinson's disease

Parkinson's disease (PD) is one of the most common neurodegenerative diseases in the world. Unfortunately, most of the currently used clinical therapies against PD are symptomatic and there is still no remedy can stop disease progression. Collective evidence shows that various kinds of exercise may reduce the risk of PD and do have positive impacts on both motor and nonmotor symptoms of PD. Additionally, exercise can also ameliorate the side effects such as wearing-off and dyskinesia induced by anti-PD therapeutics. In parallel with its benefits in ameliorating clinical symptoms, exercise modulates a range of supporting systems for brain maintenance and plasticity including neurogenesis, synaptogenesis, enhanced metabolism and angiogenesis. Exercise provides all these broad benefits on PD through inhibiting oxidative stress, repairing mitochondrial damage, and promoting the production of growth factors. Moreover, exercise reduces risk of other geriatric diseases such as diabetes, hypertension and cardiovascular disease, which may also contribute to PD pathogenesis. In summary, exercise is increasingly considered to be a complementary strategy to PD medications. In this chapter, we summarize the recent research progress on the beneficial effects of exercise on PD, discuss the underlying mechanisms, and highlight the promising prospects of exercise for antiparkinsonian therapy.

Influence of Normal Aging on Brain Autophagy: A Complex Scenario

Misfolded proteins are pathological findings in some chronic neurodegenerative disorders including Alzheimer's, Parkinson's, and Huntington's diseases. Aging is a major risk factor for these disorders, suggesting that the mechanisms responsible for clearing misfolded proteins from the brain, the ubiquitin-proteasome system and the autophagy-lysosomal pathway, may decline with age. Although autophagic mechanisms have been found to decrease with age in many experimental models, whether they do so in the brain is unclear. This review examines the literature with regard to age-associated changes in macroautophagy and chaperone-mediated autophagy (CMA) in the central nervous system (CNS). Beclin 1, LC3-II, and the LC3-II/LC3-I ratio have frequently been used to examine changes in macroautophagic activity, while lamp2a and HSPA8 (also known as hsc70) have been used to measure CMA activity. Three gene expression analyses found evidence for an age-related downregulation of macroautophagy in human brain, but no published studies were found of age-related changes in CMA in human brain, although cerebrospinal fluid concentrations of HSPA8 were reported to decrease with age. Most studies of age-related changes in brain autophagy in experimental animals have found age-related declines in macroautophagy, and macroautophagy is necessary for normal lifespan in Caenorhabditis elegans, Drosophila, and mice. However, the few studies of age-related changes in brain CMA in experimental animals have produced conflicting results. Investigations of the influence of aging on macroautophagy in experimental animals in systems other than the CNS have generally found an age-related decrease in Beclin 1, but conflicting results for LC3-II and the LC3-II/LC3-I ratio, while CMA decreases with age in most models. CONCLUSION: while indirect evidence suggests that brain autophagy may decrease with normal aging, this issue has not been investigated sufficiently, particularly in human brain. Measuring autophagic activity in the brain can be challenging because of differences in basal autophagic activity between experimental models, and the inability to include lysosomal inhibitors when measuring the LC3-II/LC3-I ratio in postmortem specimens. If autophagy does decrease in the brain with aging, then pharmacological interventions and/or lifestyle alterations to slow this decline could reduce the risk of developing age-related neurodegenerative disorders.

Exercise as a therapeutic intervention for motor and non-motor symptoms in Parkinson's disease: Evidence from rodent models

Parkinson's disease (PD) is characterised by degeneration of dopaminergic neurons of the nigrostriatal pathway, which leads to the cardinal motor symptoms of the disease - tremor, rigidity and postural instability. A number of non-motor symptoms are also associated with PD, including cognitive impairment, mood disturbances and dysfunction of gastrointestinal and autonomic systems. Current therapies provide symptomatic relief but do not halt the disease process, so there is an urgent need for preventative strategies. Lifestyle interventions such as aerobic exercise have shown potential to lower the risk of developing PD and to alleviate both motor and non-motor symptoms. However, there is a lack of large-scale randomised clinical trials that have employed exercise in PD patients. This review will focus on the evidence from studies on rodent models of PD, for employing exercise as an intervention for both motor and non-motor symptoms.

The best medicine? The influence of physical activity and inactivity on Parkinson's disease

The incidence of Parkinson's disease (PD) is expected to increase as our population ages and will likely strain the projected capacity of our health care system. Despite being the most common movement disorder, there have been few noninvasive therapeutic advances for people with PD since the first levodopa clinical trial in 1961. The study of PD pathogenesis, combined with an appreciation for the biochemical mechanisms by which physical activity and exercise may impact physiology, has resulted in emerging hypotheses for new modifiable risk factors for PD. Physical activity and exercise as a means of preventing PD, or maintaining the functionality of people with PD, are a promising area of investigation. Conversely, physical inactivity is implicated in many disease states, some of which are also correlated with the development of PD, such as metabolic syndrome. The primary relationship between these diseases is likely rooted in heightened inflammation and oxidative stress at the cellular level. Physical activity and exercise as a means of attenuating inflammation have led to increased interest in related potential therapeutic targets for PD. Ultimately, these findings may translate into low-cost, universally available therapies for PD disease modification or prevention. © 2016 International Parkinson and Movement Disorder Society.

Long-term treadmill exercise attenuates tau pathology in P301S tau transgenic mice

Background

Recent epidemiological evidence suggests that modifying lifestyle by increasing physical activity could be a non-pharmacological approach to improving symptoms and slowing disease progression in Alzheimer’s disease and other tauopathies. Previous studies have shown that exercise reduces tau hyperphosphorylation, however, it is not known whether exercise reduces the accumulation of soluble or insoluble tau aggregates and neurofibrillary tangles, which are both neuropathological hallmarks of neurodegenerative tauopathy. In this study, 7-month old P301S tau transgenic mice were subjected to 12-weeks of forced treadmill exercise and evaluated for effects on motor function and tau pathology at 10 months of age.

Results

Exercise improved general locomotor and exploratory activity and resulted in significant reductions in full-length and hyperphosphorylated tau in the spinal cord and hippocampus as well as a reduction in sarkosyl-insoluble AT8-tau in the spinal cord. Exercise did not attenuate significant neuron loss in the hippocampus or cortex. Key proteins involved in autophagy—microtubule-associated protein 1A/1B light chain 3 and p62/sequestosome 1 —were also measured to assess whether autophagy is implicated in the exercised-induced reduction of aggregated tau protein. There were no significant effects of forced treadmill exercise on autophagy protein levels in P301S mice.

Conclusions

Our results suggest that forced treadmill exercise differently affects the brain and spinal cord of aged P301S tau mice, with greater benefits observed in the spinal cord versus the brain. Our work adds to the growing body of evidence that exercise is beneficial in tauopathy, however these benefits may be more limited at later stages of disease.

A high-salt diet further impairs age-associated declines in cognitive, behavioral, and cardiovascular functions in male Fischer brown Norway rats

Aging-associated declines in cognitive, emotional, and cardiovascular function are well known. Environmental stress triggers critical changes in the brain, further compromising cardiovascular and behavioral health during aging. Excessive dietary salt intake is one such stressor. Here, we tested the effect of high salt (HS) on anxiety, learning-memory function, and blood pressure (BP) in male Fischer brown Norway (FBN) rats. Adult (A; 2 mo) and old (O; 20 mo) male rats were fed normal-salt (NS; 0.4% NaCl) or HS (8% NaCl) diets for 4 wk after being implanted with telemeter probes for conscious BP measurement. Thereafter, tests to assess anxiety-like behavior and learning-memory were conducted. The rats were then killed, and samples of plasma, urine, and brain tissue were collected. We found that systolic BP was higher in O-NS (117 ± 1.2 mm Hg) than in A-NS (105 ± 0.8 mm Hg) rats (P < 0.05). Furthermore, BP was higher in O-HS (124 ± 1.4 mm Hg) than in O-NS (117 ± 1.2 mm Hg) rats (P < 0.05). Moreover, anxiety-like behavior (light-dark and open-field tests) was not different between A-NS and O-NS rats but was greater in O-HS rats than in A-NS, O-NS, or A-HS rats (P < 0.05). Short-term memory (radial arm water maze test) was similar in A-NS and O-NS rats but was significantly impaired in O-HS rats compared with A-NS, O-NS, or A-HS rats (P < 0.05). Furthermore, oxidative stress variables (in plasma, urine, and brain) as well as corticosterone (plasma) were greater in O-HS rats when compared with A-NS, O-NS, or A-HS rats (P < 0.05). The antioxidant enzyme glyoxalase-1 expression was selectively reduced in the hippocampus and amygdala of O-HS rats compared with A-NS, O-NS, or A-HS rats (P < 0.05), whereas other antioxidant enzymes, glutathione reductase 1, manganese superoxide dismutase (SOD), and Cu/Zn SOD remained unchanged. We suggest that salt-sensitive hypertension and behavioral derangement are associated with a redox imbalance in the brain of aged FBN rats.

After the banquet: mitochondrial biogenesis, mitophagy, and cell survival

Mitochondria are highly dynamic organelles of crucial importance to the proper functioning of neuronal, cardiac and other cell types dependent upon aerobic efficiency. Mitochondrial dysfunction has been implicated in numerous human conditions, to include cancer, metabolic diseases, neurodegeneration, diabetes, and aging. In recent years, mitochondrial turnover by macroautophagy (mitophagy) has captured the limelight, due in part to discoveries that genes linked to Parkinson disease regulate this quality control process. A rapidly growing literature is clarifying effector mechanisms that underlie the process of mitophagy; however, factors that regulate positive or negative cellular outcomes have been less studied. Here, we review the literature on two major pathways that together may determine cellular adaptation vs. cell death in response to mitochondrial dysfunction. Mitochondrial biogenesis and mitophagy represent two opposing, but coordinated processes that determine mitochondrial content, structure, and function. Recent data indicate that the capacity to undergo mitochondrial biogenesis, which is dysregulated in disease states, may play a key role in determining cell survival following mitophagy-inducing injuries. The current literature on major pathways that regulate mitophagy and mitochondrial biogenesis is summarized, and mechanisms by which the interplay of these two processes may determine cell fate are discussed. We conclude that in primary neurons and other mitochondrially dependent cells, disruptions in any phase of the mitochondrial recycling process can contribute to cellular dysfunction and disease. Given the emerging importance of crosstalk among regulators of mitochondrial function, autophagy, and biogenesis, signaling pathways that coordinate these processes may contribute to therapeutic strategies that target or regulate mitochondrial turnover and regeneration.

The dynamics of the mitochondrial organelle as a potential therapeutic target

Mitochondria play a central role in cell fate after stressors such as ischemic brain injury. The convergence of intracellular signaling pathways on mitochondria and their release of critical factors are now recognized as a default conduit to cell death or survival. Besides the individual processes that converge on or emanate from mitochondria, a mitochondrial organellar response to changes in the cellular environment has recently been described. Whereas mitochondria have previously been perceived as a major center for cellular signaling, one can postulate that the organelle's dynamics themselves affect cell survival. This brief perspective review puts forward the concept that disruptions in mitochondrial dynamics--biogenesis, clearance, and fission/fusion events--may underlie neural diseases and thus could be targeted as neuroprotective strategies in the context of ischemic injury. To do so, we present a general overview of the current understanding of mitochondrial dynamics and regulation. We then review emerging studies that correlate mitochondrial biogenesis, mitophagy, and fission/fusion events with neurologic disease and recovery. An overview of the system as it is currently understood is presented, and current assessment strategies and their limitations are discussed.