Effects of Aerobic Treadmill Training on Oxidative Stress Parameters, Metabolic Enzymes, and Histomorphometric Changes in Colon of Rats with Experimentally Induced Hyperhomocysteinemia.

The aim of this study was to investigate the effects of aerobic treadmill training regimen of four weeks duration on oxidative stress parameters, metabolic enzymes, and histomorphometric changes in the colon of hyperhomocysteinemic rats. Male Wistar albino rats were divided into four groups (n = 10, per group): C, 0.9% NaCl 0.2 mL/day subcutaneous injection (s.c.) 2x/day; H, homocysteine 0.45 µmol/g b.w./day s.c. 2x/day; CPA, saline (0.9% NaCl 0.2 mL/day s.c. 2x/day) and an aerobic treadmill training program; and HPA, homocysteine (0.45 µmol/g b.w./day s.c. 2x/day) and an aerobic treadmill training program. The HPA group had an increased level of malondialdehyde (5.568 ± 0.872 µmol/mg protein, p = 0.0128 vs. CPA (3.080 ± 0.887 µmol/mg protein)), catalase activity (3.195 ± 0.533 U/mg protein, p < 0.0001 vs. C (1.467 ± 0.501 U/mg protein), p = 0.0012 vs. H (1.955 ± 0.293 U/mg protein), and p = 0.0003 vs. CPA (1.789 ± 0.256 U/mg protein)), and total superoxide dismutase activity (9.857 ± 1.566 U/mg protein, p < 0.0001 vs. C (6.738 ± 0.339 U/mg protein), p < 0.0001 vs. H (6.015 ± 0.424 U/mg protein), and p < 0.0001 vs. CPA (5.172 ± 0.284 U/mg protein)) were detected in the rat colon. In the HPA group, higher activities of lactate dehydrogenase (2.675 ± 1.364 mU/mg protein) were detected in comparison to the CPA group (1.198 ± 0.217 mU/mg protein, p = 0.0234) and higher activities of malate dehydrogenase (9.962 (5.752-10.220) mU/mg protein) were detected in comparison to the CPA group (4.727 (4.562-5.299) mU/mg protein, p = 0.0385). Subchronic treadmill training in the rats with hyperhomocysteinemia triggers the colon tissue antioxidant response (by increasing the activities of superoxide dismutase and catalase) and elicits an increase in metabolic enzyme activities (lactate dehydrogenase and malate dehydrogenase). This study offers a comprehensive assessment of the effects of aerobic exercise on colonic tissues in a rat model of hyperhomocysteinemia, evaluating a range of biological indicators including antioxidant enzyme activity, metabolic enzyme activity, and morphometric parameters, which suggested that exercise may confer protective effects at both the physiological and morphological levels.

In Situ Fluorescence Imaging Reveals Contribution of Cerebral Hydroxyl Radicals in Hyperhomocysteinemia-Induced Alzheimer-like Dementia.

Elevated plasma level of homocysteine, also termed as hyperhomocysteinemia, is acknowledged as a significant and independent risk factor of Alzheimer's disease. However, the mechanistic insight has not been thoroughly elucidated yet. In this work, 3,5-dihydroxybenzyloxy was explored as the unique reaction trigger and integrated into the naphthalimide fluorophore via a carbamate linker to afford a new probe for •OH imaging. •OH treatment induced aromatic hydroxylation and subsequent elimination reaction to release the caged fluorophore, accompanied with a highly specific and sensitive turn-on fluorescence response. Cell imaging results revealed that excess homocysteine triggered overwhelming •OH production, which was mediated by N-methyl-d-aspartate receptor and NADPH oxidase, and the resultant •OH stress further initiated neuronal ferroptosis, also confirmed by western blot analyses. Additionally, hyperhomocysteinemic mouse models were established, and Alzheimer-like dementia of the mice was observed from behavioral tests. Most importantly, with this probe, cerebral •OH fluctuation was in situ visualized in live mice, which positively correlated with the severity of Alzheimer-like dementia induced by hyperhomocysteinemia. These results reveal that cerebral •OH stress may be the critical nexus linking hyperhomocysteinemia and Alzheimer's disease. This work provides a robust fluorescence probe for in situ visualizing the cerebral •OH fluctuations and illuminating critical insights into •OH contributions in brain disorders.

Hyperhomocysteinemia Induces Rat Memory Impairment Via Injuring Hippocampal CA3 Neurons and Downregulating cAMP Response Element-Binding Protein (CREB) Phosphorylation.

Accumulated evidence demonstrated that an elevated plasma homocysteine level, hyperhomocysteinemia, induced cognitive impairment in animals, elderly and the patients with neurodegenerative diseases. To date, the underlying cellular and molecular mechanisms by which hyperhomocysteinemia induces cognitive impairment has not been clearly defined. The purpose of this study was to investigate the possible cellular and molecular mechanisms behind hyperhomocysteinemia signaling in rat memory impairment. The results from this study demonstrated that hyperhomocysteinemia induced neuronal damage and loss in hippocampal CA3 region and downregulated the cAMP response element-binding protein (CREB) phosphorylation. The findings of this study provide evidence that hyperhomocysteinemia induces rat memory impairment via injuring hippocampal CA3 neurons and downregulating CREB phosphorylation.

Effect of hyperhomocysteinemia on rat cardiac sarcoplasmic reticulum.

Increased concentration of plasma homocysteine (Hcy) is an independent risk factor of cardiovascular disease, yet the mechanism by which hyperhomocysteinemia (HHcy) causes cardiac dysfunction is largely unknown. The aim of present study was to investigate the contribution of sarcoplasmic reticulum to impaired cardiac contractile function in HHCy. HHcy-induced by subcutaneous injection of Hcy (0.45 µmol/g of body weight) twice a day for a period of 2 weeks resulted in significant decrease in developed left ventricular pressure and maximum rate of ventricular relaxation. Our results show that abundances of SR Ca2+-handling proteins, Ca2+-ATPase (SERCA2), calsequestrin and histidine-rich calcium-binding protein are significantly reduced while the content of phospholamban is unchanged. Moreover, we found that increased PLN:SERCA2 ratio results in the inhibition of SERCA2 activity at low free Ca2+ concentrations. We further discovered that HHcy is not associated with increased oxidative stress in SR. Taken together, these findings suggest that disturbances in SR Ca2+ handling, caused by altered protein contents but not oxidative damage, may contribute to impaired cardiac contractility in HHcy.

Tadalafil ameliorates memory deficits, oxidative stress, endothelial dysfunction and neuropathological changes in rat model of hyperhomocysteinemia induced vascular dementia.

AIM: The present study investigates the potential of Tadalafil, a phosphodiesterase-5 inhibitor, in a rat model of hyperhomocysteinemia induced vascular dementia. METHODS: Hyperhomocysteinemia induced vascular dementia in Wistar rats was produced by administering l-Methionine (1.7 g/kg/day; p.o.×8 weeks). Learning and memory was assessed by employing Morris water maze (MWM) test. Endothelial dysfunction was assessed through acetylcholine-induced endothelial-dependent vasorelaxation and serum nitrite levels. Various other biochemical and histopathological estimations were also performed. RESULTS: l-Methionine produced significant impairment in acetylcholine-induced endothelium-dependent vasorelaxation and a decrease in serum nitrite levels indicating endothelial dysfunction. Further, these animals performed poorly on Morris water maze, depicting impairment of learning and memory. There was a significant rise in brain oxidative stress level (indicated by an increase in brain thiobarbituric acid reactive species and a decrease in reduced glutathione levels). Increase in brain acetylcholinesterase activity; brain myeloperoxidase activity and brain neutrophil infiltration (a marker of inflammation) were also observed. Tadalafil (5 and 10 mg/kg, p.o.)/Donepezil (0.5 mg/kg, i.p., serving as standard) treatment ameliorated l-Methionine induced endothelial dysfunction; memory deficits; biochemical and histopathological changes in a significant manner. CONCLUSIONS: It may be concluded that tadalafil has shown efficacy in the rat model of l-Methionine induced vascular dementia and that phosphodiesterase-5 can be considered as an important therapeutic target for the treatment of vascular dementia.

PROTEOLYTIC ACTIVITY IN THE HEART OF RATS WITH HYPERHOMOCYSTEINEMIA.

OBJECTIVE: The aim: To investigate the distribution of proteolytic activity and cytokine profile in the heart of rats with hyperhomocysteinemia. PATIENTS AND METHODS: Materials and methods: A total of 60 albino non-linear male rats was used in the study. Hyperhomocysteinemia was induced by intragastric administration of DL-homocysteine thiolactone. Total proteolytic activity was measured using casein as a substrate. To determine the activity of metal-dependent and serine proteases, ethylenediaminetetraacetic acid, and phenylmethylsulfonyl fluoride were used. The level of matrix metalloproteinases, tissue inhibitor of metalloproteinases-1, and cytokines was studied by enzyme-linked immunosorbent assay. RESULTS: Results: It was found an increase in the total proteolytic activity in the heart of young, adult, and old animals. In addition, the redistribution of proteolytic activity was revealed - the portion of metal-dependent enzymes increased in all groups while the percentage of serine proteases decreased in the old animals with hyperhomocysteinemia. The state of mild inflammation, evidenced by the increased level of some pro-inflammatory cytokines, was found in the heart of young and old animals with hyperhomocysteinemia. CONCLUSION: Conclusions: The pathogenesis of hyperhomocysteinemia is accompanied by a change in the proteolytic activity in the heart as well as a change in the cytokine profile.

THE INFLUENCE OF CHRONIC HYPERHOMOCYSTEINEMIA ON PHAGOCYTIC AND METABOLIC ACTIVITY OF PERIPHERAL BLOOD NEUTROPHILS IN CASE OF LIPOPOLYSACCHARIDE-INDUCED PERIODONTITIS.

The aim of the study was to investigate the phagocytic and metabolic activity of peripheral blood neutrophils in rats with lipopolysaccharide (LPS)-induced periodontitis combined with chronic thiolactone hyperhomocysteinemia (HHcy).The experiment included non-linear mature male rats (n=48), which were divided into 4 groups: control; animals with a periodontitis model; animals with a model of chronic thiolactone HHcy; animals with a model of periodontitis in combination with chronic thiolactone HHcy. Phagocytic activity, phagocytic index and phagocytic number were determined as indicators of phagocytosis of peripheral blood neutrophils. The oxygen-dependent bactericidal activity of peripheral blood neutrophils was studied using nitroblue tetrazolium test (NBT-test).Our research has found that LPS-induced periodontitis in rats is accompanied by dysfunction of phagocytosis process (increased phagocytic activity with a simultaneous decrease of absorption capacity) and activation of oxygen-dependent microbicidal mechanisms of peripheral blood neutrophils, as indicated by an increase of indices of spontaneous and activated NBT-test. Chronic thiolactone HHcy adversely affects the functional and metabolic activity of peripheral blood neutrophils in case of periodontitis, which is confirmed by a violation of the process of phagocytosis, a more pronounced decrease in absorption capacity and depletion of metabolic reserves of these cells in rats with comorbid course of LPS-induced periodontitis vs. animals with only LPS-induced periodontitis. The observed disorders in the process of phagocytosis in rats with comorbid course of periodontitis are an important factor in reducing the non-specific organism resistance which contributes to the progression of periodontitis. The obtained results reveal new aspects of the high Hcys plasma level influence on the course of inflammatory process in periodontal tissues, which opens opportunities for improving pathogenetic therapy in patients with periodontal disease combined with chronic HHcy.

Neurotrophins of the Fetal Brain and Placenta in Prenatal Hyperhomocysteinemia.

Prenatal hyperhomocysteinemia (PHHC) in pregnant rats was induced by chronic L-methionine loading, resulting in a significant increase in the L-homocysteine content both in the mothers' blood and blood and brain of fetuses. Significant decrease in the weight of the placenta, fetus, and fetal brain was detected by the morphometric studies on day 20 of pregnancy. PHHC also activated maternal immune system due to the increase in the content of proinflammatory interleukin-1ß in the rat blood and fetal part of the placenta. PHHC elevated the levels of the brain-derived neurotrophic factor (BDNF, 29 kDa) and nerve growth factor (NGF, 31 kDa) precursors in the placenta and the content of the BDNF isoform (29 kDa) in the fetal brain. The content of neuregulin 1 (NRG1) decreased in the placenta and increased in the fetal brain on day 20 of embryonic development. An increase in the caspase-3 activity was detected in the brains of fetuses subjected to PHHC. It was suggested that changes in the processing of neurotrophins induced by PPHC, oxidative stress, and inflammatory processes initiated by it, as well as apoptosis, play an important role in the development of brain disorders in the offspring.

Implementation of programmed cell death in circulating neutrophils and its special characteristics in experimentally induced hyperhomocysteinemia in a setting of thyroid dysfunction.

Cardiovascular (CV) disease continues to be the main cause of morbidity and mortality in worldwide. Hyperhomocysteinemia (HHCy) is a novel metabolic risk factor of vascular damage. In addition to that, there is evidence that HHCy management with folic acid and vitamin B supplements prevents atherosclerosis and its sequelae. Oxidative stress is one of the mechanisms behind the cardiotoxic effects of high homocysteine levels. On the one hand, HHCy facilitates endothelial dysfunction, probably as a result of impaired synthesis and/or inactivation of nitrogen (II) oxide (NO). On the other hand, oxidation of homocysteine is accompanied by formation of reactive oxygen species (ROS), which induce lipid peroxidation in cell membranes and in low density lipoproteins, mitochondrial membrane, secretion of cytochrome C and activation of caspase-3, culminating in apoptosis. Thyroid hormones are known to have a profound effect on CV functions. Hyperthyroidism causes heart rate, myocardial contractility and ejection fraction to increase; this may result in systolic hypertension, systolic heart murmurs, increased left ventricular weight and development of angina and atrial fibrillation with a risk for stroke. AIM: The aim of our work was to investigate into the special aspects that characterize implementation of programmed cell death in circulating neutrophils of HHCy rats either without comorbidities or with hyper- or hypothyroidism. MATERIALS AND METHODS: Prolonged hyperthyroidism and hypothyroidism were modeled in experimental rats by dosing the animals with Lthyroxine and thiamazole, respectively, for 21 days, and prolonged with HHCy administered with excessive exogenous HCy, for 21 days. Prolonged HHCy rats with hyper- or hypothyroidism were observed. RESULTS: We have found the count of circulating neutrophils with increased ROS production and reduced transmembrane mitochondrial potential to be significantly increased in rats with HHCy compared to control animals, which suggests prooxidant properties of HCy and its ability to cause mitochondrial dysfunction. The intensity of ROS production by circulating neutrophils in hyperthyroid animals with HHCy was not significantly different from that in hyperthyroid rats without HHCy. In hypothyroid rats with HHCy, ROS production by circulating neutrophils was significantly higher compared to the control group. HCys increased ROS generation in kidney mitochondria while strongly decreasing it in liver, heart and brain mitochondria showing that the changes are tissue-specific. We have found the count of circulating neutrophils with signs of apoptosis to be increased in rats with HHCy compared to the control group. CONCLUSIONS: Experimentally induced HHCy is accompanied by hyperproduction of reactive oxygen species and by impaired integrity of external mitochondrial membrane, which results in initiation of apoptotic cell death. The deficiency of thyroid hormones enhances initiation of programmed cell death.

Effect of Methionine Diet on Metabolic and Histopathological Changes of Rat Hippocampus.

Hyperhomocysteinemia (hHcy) is regarded as an independent and strong risk factor for cerebrovascular diseases, stroke, and dementias. The hippocampus has a crucial role in spatial navigation and memory processes and is being constantly studied for neurodegenerative disorders. We used a moderate methionine (Met) diet at a dose of 2 g/kg of animal weight/day in duration of four weeks to induce mild hHcy in adult male Wistar rats. A novel approach has been used to explore the hippocampal metabolic changes using proton magnetic resonance spectroscopy (1H MRS), involving a 7T MR scanner in combination with histochemical and immunofluorescence analysis. We found alterations in the metabolic profile, as well as remarkable histo-morphological changes such as an increase of hippocampal volume, alterations in number and morphology of astrocytes, neurons, and their processes in the selective vulnerable brain area of animals treated with a Met-enriched diet. Results of both methodologies suggest that the mild hHcy induced by Met-enriched diet alters volume, histo-morphological pattern, and metabolic profile of hippocampal brain area, which might eventually endorse the neurodegenerative processes.

Anti-Ischemic Activity of Triamine ALM-802 under Conditions of Endothelial Dysfunction.

Anti-ischemic activity of N1-(2,3,4-trimethoxybenzyl)-N2-{2-[(2,3,4-trimethoxybenzyl)amino] ethyl}-1,2-ethanediamine (ALM-802) based on the structure of standard p-FOX inhibitors trimetazidine and ranolazine was studied on the model of endocardial ischemia in intact rats and animals with endothelial dysfunction. Acute endocardial myocardial ischemia was caused by infusion of isoproterenol (20 µg/kg/min intravenously). Endothelial dysfunction in rats was modeled by inducing hyperhomocysteinemia (3 g/kg methionine intragastrically one a day over 7 days). The reference drugs trimetazidine (30 mg/kg, intravenously) and ranolazine 10 mg/kg, intravenously) that were effective only in intact rats. In contrast, ALM-802 (2 mg/kg, intravenously) showed a pronounced anti-ischemic effect in animals with endothelial dysfunction, which suggests that the mechanisms of its cardioprotective action differ from those known for p-FOX inhibitors.

Diet-induced hyperhomocysteinemia impairs vasodilation in 5/6-nephrectomized rats.

Plasma homocysteine is elevated in patients with impaired renal function, and markedly so at end-stage renal disease. As chronic kidney disease and hyperhomocysteinemia are also independent risk factors for cardiovascular disease, the latter is hypothesized to accelerate vascular abnormalities following renal failure. This study aimed to investigate the combined effect of impaired renal function and hyperhomocysteinemia on vascular function. We show that in 5/6-nephrectomized rats, a model of chronic kidney disease, a methionine-rich diet for 8 weeks induces moderate hyperhomocysteinemia, exacerbates hypertension, and attenuates the vascular response to acetylcholine, sodium nitroprusside, 8-bromo-cGMP, and isoprenaline. However, plasma nitrate/nitrite and total NOS activity in the thoracic aorta were not affected. Collectively, the data imply that hyperhomocysteinemia and end-stage renal disease synergistically impair endothelium-dependent and endothelium-independent vasodilatation by blocking the cGMP/protein kinase G and/or cAMP/protein kinase A pathways. 5/6-Nephrectomized rat with hyperhomocysteinemia induced by a methionine-rich diet would be a useful model for elucidating the pathogenesis of vascular impairment in patients with end-stage renal disease.

Association of Induced Hyperhomocysteinemia with Alzheimer's Disease-Like Neurodegeneration in Rat Cortical Neurons After Global Ischemia-Reperfusion Injury.

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disorder that results in massive hippocampal and neocortical neuronal loss leading to dementia and eventual death. The exact cause of Alzheimer's disease is not fully explored, although a number of risk factors have been recognized, including high plasma concentration of homocysteine (Hcy). Hyperhomocysteinemia (hHcy) is considered a strong, independent risk factor for stroke and dementia. However, the molecular background underlying these mechanisms linked with hHcy and ischemic stroke is not fully understood. Paper describes rat model of global forebrain ischemia combined with the experimentally induced hHcy. Global ischemia-reperfusion injury (IRI) was developed by 4-vessels occlusion lasting for 15 min followed by reperfusion period of 72 h. hHcy was induced by subcutaneous injection of 0.45 µmol/g of Hcy in duration of 14 days. The results showed remarkable neural cell death induced by hHcy in the brain cortex and neurodegeneration is further aggravated by global IRI. We demonstrated degeneration of cortical neurons, alterations in number and morphology of tissue astrocytes and dysregulation of oxidative balance with increased membrane protein oxidation. Complementary to, an immunohistochemical analysis of tau protein and ß-amyloid peptide showed that combination of hHcy with the IRI might lead to the progression of AD-like pathological features. Conclusively, these findings suggest that combination of risk factor hHcy with IRI aggravates neurodegeneration processes and leads to development of AD-like pathology in cerebral cortex.

Effects of atorvastatin and simvastatin on oxidative stress in diet-induced hyperhomocysteinemia in Wistar albino rats: a comparative study.

Considering the well-known antioxidant properties of statins, it seems important to assess their impact on major markers of oxidative stress (superoxide anion radical, nitric oxide, and index of lipid peroxidation) to compare the antioxidative potentials of atorvastatin and simvastatin during the different degrees of hyperhomocysteinemia (HHcy) in rats. This study was conducted on adult male Wistar albino rats (n = 90; 4 weeks old; 100 ± 15 g body mass) in which HHcy was achieved by dietary manipulation. For 4 weeks, the animals were fed with one of the following diets: standard rodent chow, diet enriched in methionine with no deficiency in B vitamins (folic acid, B6, and B12), or diet enriched in methionine and deficient in B vitamins (folic acid, B6, and B12). At the same time, animals were treated with atorvastatin at doses of 3 mg/kg/day i.p. or simvastatin at doses of 5 mg/kg/day i.p. Levels of superoxide anion radical and TBARS were significantly decreased by administration of simvastatin in normal and high-homocysteine (Hcy) groups (p < 0.05). At 4 weeks after feeding with purified diets, the concentrations of the GSH, CAT, and SOD antioxidants were significantly affected among all groups (p < 0.05). Our results indicated that statin therapy had variable effects on the redox status in hyperhomocysteinemic rats, and simvastatin demonstrated stronger antioxidant effects than did atorvastatin.

Vitamin B complex mitigates cardiac dysfunction in high-methionine diet-induced hyperhomocysteinemia.

This research is designed to test the hypothesis that elevated homocysteine (Hcy) levels in vivo, caused by a deficit in vitamin B complex, promote changes in cardiac function and redox status that lead to heart failure. In order to conduct the study, we used adult male Wistar albino rats (n = 30; 4 weeks old; 100 ± 15 g body weight). Hyperhomocysteinaemia (HHcy) in these animals was achieved by dietary manipulation. For 4 weeks, the animals were fed with a standard rodent chow (control, CF), a diet enriched in methionine with no deficiency in B vitamins (i.e., folic acid, B6 and B12) (HMNV) or a diet enriched in methionine and deficient in B vitamins (HMLV). After 28 days of dietary manipulation, all animals were killed. The rat hearts were isolated and retrogradely perfused according to the Langendorff technique at a gradually increasing perfusion pressure. We found a negative correlation between elevated serum Hcy and total body and heart weight. The maximum rate of left ventricular pressure development was significantly increased in the HMNV group compared with in the other groups. Systolic left ventricular pressure was significantly changed in all groups. HHcy induces remodelling of the cardiac tissues, as moderate HHcy is associated with more prominent interstitial and perivascular fibrosis. Our results suggest that a high methionine diet without vitamin B complex causes profound negative effects associated with HHcy.

Efficacy of Folic Acid and Vitamin B12 Replacement Therapies in the Reduction of Adverse Effects of Isotretinoin: A Randomized Controlled Trial.

Previous studies have reported elevated homocysteine levels and folic acid and/or vitamin B12 deficiencies after isotretinoin therapy, which increase the risk of cardiovascular and neuropsychiatric disorders. Homocysteine is metabolized in the liver, a process requiring folate and vitamin B12. We conducted a randomized controlled trial to investigate whether folate and vitamin B12 replacement therapy with isotretinoin would be useful for preventing hyperhomocysteinemia. A total of 66 patients with acne were randomized into two groups: group A took isotretinoin, folic acid, and vitamin B12, whereas group B took isotretinoin alone. Treatment was continued for 2 months. Blood homocysteine, folic acid, and vitamin B12 levels were measured before and after treatment. In group A, a significant decrease in homocysteine level was observed after treatment (P=.0004), although it was still within the normal range. Folic acid and vitamin B12 levels significantly increased (P=.0026 and P=.0002, respectively). In group B, no significant changes were observed in the levels of homocysteine and vitamin B12, but folic acid levels decreased significantly (P=.02). We concluded that folic acid and vitamin B12 supplementation during isotretinoin therapy could be useful for preventing folate deficiency and improving blood homocysteine levels; this might as a result reduce the risks for cardiovascular and neuropsychiatric disorders in patients taking isotretinoin.

L-DOPA-induced hyperhomocysteinemia in Parkinson's disease: Elephant in the room.

BACKGROUND: Dopamine replacement therapy by its precursor, L-3.4-dihydroxyphenylalanine (L-DOPA), has been the treatment of choice for Parkinson's disease. However, the possible contributory effect of L-DOPA therapy on the progression of Parkinson's disease mediated by the L-DOPA-induced toxic metabolites remains elusive. SCOPE OF REVIEW: Prolong use of L-DOPA leads to behavioral impediments and instigate the generation of several toxic metabolites. One such metabolite is homocysteine, the level of which increases in the plasma of Parkinson's disease patients undergoing L-DOPA therapy, as well as in brain of animal models of the disease. In concoction with parkinsonian neurotoxins, Hcy exaggerates dopaminergic neurodegeneration, while its intranigral infusion has been demonstrated to decrease the dopamine level as well as causes dopaminergic neurodegeneration. Therefore, it can be propounded that elevated level of Hcy (hyperhomocysteinemia) is one of the underlying causes of L-DOPA-induced side-effects and aggravates the progressive nature of Parkinson's disease, which has been focused here. We have provided a conjectural discussion on the involvement of Hcy in L-DOPA-induced dyskinesia in Parkinson's disease. CONCLUSION: Hyperhomocysteinemia as a result of prolonged L-DOPA therapy is the emerging cause of L-DOPA-induced behavioral abnormalities and progressive nature of Parkinson's disease. GENERAL SIGNIFICANCE: This review highlights that hyperhomocysteinemia could be a putative contributor of the side-effects of chronic L-DOPA therapy because of its neurotoxic potency.

Increased myoendothelial feedback is associated with increased connexin37 and IK1 channel expression in mesenteric arteries of diet-induced hyperhomocysteinemic mice.

OBJECTIVE: Previously, we found that diet-induced HHcy in mice caused decreased eNOS expression and signaling in mesenteric arteries, but greatly enhanced non-NOS, non-prostacyclin-dependent vasodilation, which involves MEJ communication. To further assess whether HHcy enhances MEJ communication, this study examined endothelium-dependent attenuation of phenylephrine-induced vasoconstriction (myoendothelial feedback) and key molecules involved. METHODS: Myoendothelial feedback was examined in isolated mouse mesenteric arteries, after 6-weeks diet-induced HHcy, using pressure myography. Gap junction (Cx37, Cx40, Cx43), NOS (eNOS, nNOS, iNOS), and potassium channel (IK1) protein expression were measured with immunoblots, and connexin mRNAs with real-time PCR. Contribution of nNOS + iNOS to vasomotor responses was assessed using the drug TRIM. RESULTS: Myoendothelial feedback was significantly (P < .05) enhanced in HHcy arteries compared to control, coincident with significantly greater Cx37 and IK1 protein and Cx37 mRNA. Cx43 protein, but not mRNA, was significantly less in HHcy, and Cx40 was not different. eNOS protein was significantly less in HHcy. nNOS and iNOS were not different. TRIM had little effect on vasomotor function. CONCLUSIONS: Diet-induced HHcy enhanced myoendothelial feedback, and increased Cx37 and IK1 expression may contribute. nNOS or iNOS did not upregulate to compensate for decreased eNOS, and they had little involvement in vasomotor function.

Effects of fisetin on hyperhomocysteinemia-induced experimental endothelial dysfunction and vascular dementia.

This study was designed to investigate the effects of fisetin (FST) on hyperhomocysteinemia (HHcy)-induced experimental endothelial dysfunction (ED) and vascular dementia (VaD) in rats. Wistar rats were randomly divided into 8 groups: control, vehicle control, l-methionine, FST (5, 10, and 25 mg/kg, p.o.), FST-per se (25 mg/kg, p.o.), and donepezil (0.1 mg/kg, p.o.). l-Methionine administration (1.7 g/kg, p.o.) for 32 days induced HHcy. ED and VaD induced by HHcy were determined by vascular reactivity measurements, behavioral analysis using Morris water maze and Y-maze, along with a biochemical and histological evaluation of thoracic aorta and brain tissues. Administration of l-methionine developed behavioral deficits; triggered brain lipid peroxidation (LPO); compromised brain acetylcholinesterase activity (AChE); and reduced the levels of brain superoxide dismutase (SOD), brain catalase (CAT), brain reduced glutathione (GSH), and serum nitrite; and increased serum homocysteine and cholesterol levels. These effects were accompanied by decreased vascular NO bioavailability, marked intimal thickening of the aorta, and multiple necrotic foci in brain cortex. HHcy-induced alterations in the activities of SOD, CAT, GSH, AChE, LPO, behavioral deficits, ED, and histological aberrations were significantly attenuated by treatment with fisetin in a dose-dependent manner. Collectively, our results indicate that fisetin exerts endothelial and neuroprotective effects against HHcy-induced ED and VaD.

The Cardiovascular Effect of Systemic Homocysteine Is Associated with Oxidative Stress in the Rostral Ventrolateral Medulla.

It has been demonstrated that homocysteine (HCY) is a significant risk factor of hypertension, which is characterized by overactivity of sympathetic tone. Excessive oxidative stress in the rostral ventrolateral medulla (RVLM), a key region for control of sympathetic outflow, contributes to sympathetic hyperactivity in hypertension. Therefore, the goal of the present study is to determine the effect of systemic HCY on production of reactive oxygen species (ROS) in the RVLM. In the rat model of the diet-induced hyperhomocysteinemia (L-methionine, 1 g/kg/day, 8 weeks), we found that the HCY resulted in a significant increase (≈3.7-fold, P < 0.05) in ROS production in the RVLM, which was paralleled with enhanced sympathetic tone and blood pressure (BP). Compared to the vehicle group, levels of BP and basal renal sympathetic nerve activity in the HCY group were significantly (P < 0.05, n = 5) increased by an average of 27 mmHg and 31%, respectively. Furthermore, the rats treated with L-methionine (1 g/kg/day, 8 weeks) showed an upregulation of NADPHase (NOX4) protein expression and a downregulation of superoxide dismutase protein expression in the RVLM. The current data suggest that central oxidative stress induced by systemic HCY plays an important role in hypertension-associated sympathetic overactivity.