RETRACTED: Serebrovska et al. Intermittent Hypoxia-Hyperoxia Training Improves Cognitive Function and Decreases Circulating Biomarkers of Alzheimer's Disease in Patients with Mild Cognitive Impairment: A Pilot Study. Int. J. Mol. Sci. 2019, 20, 5405.

The journal Int [...].

Quercetin inhibits the expression of MYC and CYP2E1 and reduces oxidative stress in the myocardium of spontaneously hypertensive rats.

Oxidative stress is one of the most important pathological processes in chronic heart failure caused by hypertension. These processes involve MYC-regulated mechanisms, including the induction of CYP2E1 as a potent prooxidant factor. In this work, we used qPCR, Western blot analysis, and biochemical markers of oxidative stress to investigate the ability of quercetin to inhibit oxidative stress by modulating MYC expression. We studied spontaneously hypertensive rats (SHRs) in which the onset of cardiac pathology was observed at least at 4 months of age and the development of pathology occurred during life up to 22 months of age. Wistar rats were used as normotensive controls. We observed overexpression of the transcription factor MYC (p=0.0024) in the myocardium of SHRs compared to normotensive controls, and an increased expression of MYC-target gene, CYP2E1, (p=0.0001) in the old SHR group compared to young SHRs. This probably contributed significantly to the development of oxidative stress in the cardiac tissue of old SHRs. We demonstrated that long-term treatment of old SHRs with quercetin resulted in dramatic inhibition of MYC (p=0.0000), and a significant decrease in CYP2E1 (p=0.0001) expression and CYP2E1 protein levels (p=0.0136). This probably contributed significantly to the decrease in lipid peroxidation (p=0.0000). Quercetin was also able to activate antioxidant activity, resulting in a significant improvement in the prooxidant-antioxidant balance in the heart. In turn, the elimination of oxidative stress could contribute to a decrease in blood pressure (p=0.0000) and relative heart weight (p=0.0071) in quercetin-treated old SHRs compared to the untreated old SHR group.

Treatment with omega-3 PUFAs does not increase the risk of CYP2E1-dependent oxidative stress and diabetic liver pathology.

An increase in CYP2E1 expression is a key factor in the development of diabetic oxidative liver damage. Long-term treatment with omega-3 PUFAs, which are CYP2E1 substrates, may affect CYP2E1 expression in the liver. In this work, we performed Western blot analysis, biochemical methods, and microscopic ultrastructural studies of the liver in a streptozotocin-induced rat model of type 1 diabetes to investigate whether long-term treatment with omega-3 PUFAs could induce CYP2E1-dependent oxidative stress and diabetic liver pathology. Significant hyperglycemia and lack of natural weight gain were observed in the diabetic rats compared to non-diabetic controls. A 2.5-fold increase in CYP2E1 expression (protein content and activity) was also observed in the diabetic rats. In addition, signs of oxidative stress were found in the liver of the diabetic rats. A significant increase in transaminases and GGT level in blood serum was also observed, which could indicate marked destruction of liver tissue. Diabetic dyslipidemia (increased triacylglycerol levels and decreased HDL-C levels) was found. Treatment of the diabetic animals with an omega-3-enriched pharmaceutical composition of PUFAs had no effect on CYP2E1 levels but contributed to a two-fold decrease in enzyme activity. The intensity of lipid peroxidation also remained close to the diabetic group. However, at the same time, antioxidant protection was provided by induction of antioxidant enzyme activity. Examination of the liver ultrastructure revealed no characteristic signs of diabetic pathology. However, omega-3 PUFAs did not normalize blood glucose levels and serum lipid profile. Thus, long-term treatment of diabetic rats with omega-3 PUFAs does not increase the risk of CYP2E1-dependent oxidative stress and development of liver pathology but prevents some diabetic ultrastructural damage to hepatocytes.

Response of Circulating Inflammatory Markers to Intermittent Hypoxia-Hyperoxia Training in Healthy Elderly People and Patients with Mild Cognitive Impairment.

Intermittent hypoxia-hyperoxia training (IHHT) is a non-pharmacological therapeutic modality for management of some chronic- and age-related pathologies, such as Alzheimer's disease (AD). Our previous studies demonstrated significant improvement of cognitive function after IHHT in the patients with mild cognitive impairment (MCI). The present study further investigated the effects of IHHT on pro-inflammatory factors in healthy elderly individuals and patients with early signs of AD. Twenty-nine subjects (13 healthy subjects without signs of cognitive impairment syndrome and 16 patients diagnosed with MCI; age 52 to 76 years) were divided into four groups: Healthy+Sham (n = 7), Healthy+IHHT (n = 6), MCI+Sham (n = 6), and MCI+IHHT (n = 10). IHHT was carried out 5 days per week for 3 weeks (total 15 sessions), and each daily session included 4 cycles of 5-min hypoxia (12% FIO2) and 3-min hyperoxia (33% FIO2). Decline in cognitive function indices was observed initially in both MCI+Sham and MCI+IHHT groups. The sham training did not alter any of the parameters, whereas IHHT resulted in improvement in latency of cognitive evoked potentials, along with elevation in APP110, GDF15 expression, and MMP9 activity in both healthy subjects and those with MCI. Increased MMP2 activity, HMGB1, and P-selectin expression and decreased NETs formation and Aß expression were also observed in the MCI+IHHT group. There was a negative correlation between MoCA score and the plasma GDF15 expression (R = −0.5799, p < 0.05) before the initiation of IHHT. The enhanced expression of GDF15 was also associated with longer latency of the event-related potentials P330 and N200 (R = 0.6263, p < 0.05 and R = 0.5715, p < 0.05, respectively). In conclusion, IHHT upregulated circulating levels of some inflammatory markers, which may represent potential triggers for cellular adaptive reprogramming, leading to therapeutic effects against cognitive dysfunction and neuropathological changes during progression of AD. Further investigation is needed to clarify if there is a causative relationship between the improved cognitive function and the elevated inflammatory markers following IHHT.

Intermittent Hypoxia-Hyperoxia Training Improves Cognitive Function and Decreases Circulating Biomarkers of Alzheimer's Disease in Patients with Mild Cognitive Impairment: A Pilot Study.

Alzheimer's disease (AD) affects not only the central nervous system, but also peripheral blood cells including neutrophils and platelets, which actively participate in pathogenesis of AD through a vicious cycle between platelets aggregation and production of excessive amyloid beta (Aß). Platelets adhesion on amyloid plaques also increases the risk of cerebral microcirculation disorders. Moreover, activated platelets release soluble adhesion molecules that cause migration, adhesion/activation of neutrophils and formation of neutrophil extracellular traps (NETs), which may damage blood brain barrier and destroy brain parenchyma. The present study examined the effects of intermittent hypoxic-hyperoxic training (IHHT) on elderly patients with mild cognitive impairment (MCI), a precursor of AD. Twenty-one participants (age 51-74 years) were divided into three groups: Healthy Control (n = 7), MCI+Sham (n = 6), and MCI+IHHT (n = 8). IHHT was carried out five times per week for three weeks (total 15 sessions). Each IHHT session consisted of four cycles of 5-min hypoxia (12% FIO2) and 3-min hyperoxia (33% FIO2). Cognitive parameters, Aß and amyloid precursor protein (APP) expression, microRNA 29, and long non-coding RNA in isolated platelets as well as NETs in peripheral blood were investigated. We found an initial decline in cognitive function indices in both MCI+Sham and MCI+IHHT groups and significant correlations between cognitive test scores and the levels of circulating biomarkers of AD. Whereas sham training led to no change in these parameters, IHHT resulted in the improvement in cognitive test scores, along with significant increase in APP ratio and decrease in Aß expression and NETs formation one day after the end of three-week IHHT. Such effects on Aß expression and NETs formation remained more pronounced one month after IHHT. In conclusion, our results from this pilot study suggested a potential utility of IHHT as a new non-pharmacological therapy to improve cognitive function in pre-AD patients and slow down the development of AD.

Spinal PKCα inhibition and gene-silencing for pain relief: AMPAR trafficking at the synapses between primary afferents and sensory interneurons.

Upregulation of Ca2+-permeable AMPA receptors (CP-AMPARs) in dorsal horn (DH) neurons has been causally linked to persistent inflammatory pain. This upregulation, demonstrated for both synaptic and extrasynaptic AMPARs, depends on the protein kinase C alpha (PKCα) activation; hence, spinal PKC inhibition has alleviated peripheral nociceptive hypersensitivity. However, whether targeting the spinal PKCα would alleviate both pain development and maintenance has not been explored yet (essential to pharmacological translation). Similarly, if it could balance the upregulated postsynaptic CP-AMPARs also remains unknown. Here, we utilized pharmacological and genetic inhibition of spinal PKCα in various schemes of pain treatment in an animal model of long-lasting peripheral inflammation. Pharmacological inhibition (pre- or post-treatment) reduced the peripheral nociceptive hypersensitivity and accompanying locomotive deficit and anxiety in rats with induced inflammation. These effects were dose-dependent and observed for both pain development and maintenance. Gene-therapy (knockdown of PKCα) was also found to relieve inflammatory pain when applied as pre- or post-treatment. Moreover, the revealed therapeutic effects were accompanied with the declined upregulation of CP-AMPARs at the DH synapses between primary afferents and sensory interneurons. Our results provide a new focus on the mechanism-based pain treatment through interference with molecular mechanisms of AMPAR trafficking in central pain pathways.

Quercetin prevents type 1 diabetic liver damage through inhibition of CYP2E1.

BACKGROUND: Increased CYP2E1 protein and activity levels can be the main cause of stress-mediated liver damage in diabetes. In this work we investigated the quercetin properties to prevent diabetic oxidative liver injury through inhibition of CYP2E1. METHODS: Animals were randomly divided into three groups (n=5 for each group): non-diabetic control, STZ-diabetic rats and STZ-diabetic rats administered with quercetin (50mg/kg bw, per day, during 30days). Markers of oxidative stress and liver injury, hepatocyte ultrastructure and levels of CYP2E1 protein and activity were examined using biochemical, electron microscopy and molecular biological methods. RESULTS: It was shown that symptoms of diabetes (hyperglycemia, bodyweight loss, damaged hepatocyte ultrastructure), signs of oxidative stress in liver (2-fold intensification of peroxide process and 2-fold depletion of antioxidants) and serum markers of liver damage (3.5-, 1.5- and 5-fold increase in levels of ALT, AST and GGT, respectively) were present in STZ-diabetic rats. We found 3- and 2.5-fold increase in levels of protein and activity of CYP2E1 in the liver of STZ-diabetic rats. We demonstrated that the administration of quercetin leads to significant decrease in CYP2E1 activity (5- and 2-times compared to STZ-diabetic and control group, respectively). That was accompanied by normalization of pro-oxidant-antioxidant balance, improving the ultrastructure of hepatocytes and rates of serum markers of liver injury. CONCLUSIONS: CYP2E1 can play a crucial role in stress-induced pathological processes in the liver in diabetes, and the inhibition of the enzyme by quercetin during the development of diabetes mainly prevents the oxidative damage in liver.

N-3 long chain polyunsaturated fatty acids increase the expression of PPARγ-target genes and resistance of isolated heart and cultured cardiomyocytes to ischemic injury.

BACKGROUND: The goal of present investigation is to check the hypothesis that cardioprotective effect of polyunsaturated fatty acids (PUFAs) is mediated by influence on mRNA expression level of the FATP, IL-1ra and GJP43 through stimulation of PPARγ. METHODS: Animals obtained n-3 PUFAs orally during 4 weeks (0.1ml/100g b.w. per day) or during prenatal period. In experiments, isolated perfused hearts were subjected to 20-min regional ischemia and 40min reperfusion. The hearts of newborn rats (2-3days old) were used for isolated cardiomyocytes culture preparing. Culture cells underwent 30min of anoxia followed by 60min of reoxygenation. Using rtPCR the level of FATP, IL-1ra, GJP43 and BCL2 mRNA in isolated cardiomyocyte and hearts was evaluated. RESULTS: The data obtained indicate that in heart tissues from pups with prenatal n-3 PUFAs application the level of LA and DHA acids were increased in 3.6-fold and 2-fold correspondingly comparing to control. In adult hearts the level of DHA was increased in 1.4-fold, and the level of EPA-in 6.9-fold. We observed the increase in mRNA level of PPARγ-target genes: FATP in 2.25 times, and IL-1ra in 8.4 times. At the same time the level of mRNA of antiapoptotic gene BCL2 was increased in 2.13 times and Connexin-43 gene in 2.2 times after n-3 PUFAs application. These effects were accompanied by significantly improved cardiac function, and increase of living cardiomyocytes number at modeling of ischemia-reperfusion. CONCLUSIONS: n-3 PUFAs application has cardioprotective effects and increases mRNA level of FATP, IL-1ra, GJP43, and BCL2 genes in culture of neonatal cardiomyocytes and in adult hearts.

Dietary Omega-3 Polyunsaturated Fatty Acids Alter Fatty Acid Composition of Lipids and CYP2E1 Expression in Rat Liver Tissue.

Omega-3 polyunsaturated fatty acids (PUFAs) are used for the treatment and prevention of numerous pathologies in humans. As recently found, PUFAs play significantly protective roles in liver, cardiovascular system and kidney. They also are widely used in total parenteral nutrition. We evaluated the effect of omega-3 PUFA consumption on liver fatty acid composition and the expression of CYP2E1, one of the key enzymes in detoxification and prooxidant systems of liver cells. To estimate the oxidative stress in liver tissue, the antioxidant status and the level of lipid peroxidation were determined in a rodent model. Animals were divided into two groups: control (n = 10) and experimental (n = 10). Epadol-containing omega-3 PUFA fish oil capsules were administered to Wistar rats within 4 weeks (0.1 mL/100 g b.w./day). The consumption of omega-3 PUFAs resulted in changes of fatty acid composition of liver tissue. A significant increase was detected in the α-linolenic, eicosapentaenoic and docosahexaenoic acid content (5.1-, 16-, and 1.3-fold, respectively, p < 0.05), while the content of linoleic and arachidonic acid was reduced (1.7- and 3.2-fold, respectively, p < 0.05). This caused significant increases in the omega-3:omega-6 ratio. Consumption of omega-3 PUFAs led to a 3-fold (p < 0.05) increase in CYP2E1 content, which could entail enhanced Nrf2 expression levels and increases in the HO-1 content in rat liver. The alteration in CYP2E1 expression did not have an impact on the level of lipid peroxidation and on the prooxidant/antioxidant balance.

Omega-3 polyunsaturated fatty acid-enriched diet differentially protects two subpopulations of myocardial mitochondria against Ca(2+)-induced injury.

Omega-3 polyunsaturated fatty acids (PUFA) confer protection against myocardial injury after ischemia-reperfusion. There are two subfractions of mitochondria located in different regions of the cell: subsarcolemmal mitochondria (SSM) and interfibrillar mitochondria (IFM). The present study explored possible differences between Ca(2+)-induced mitochondrial swelling in rat SSM and IFM fractions under control conditions (control group [CG]) and after dietary supplementation with omega-3 PUFA (experimental group [EG]). Changes in mitochondrial matrix volumes were measured using the light-scattering technique. In the CG, the time courses of swelling were comparable in both mitochondrial fractions, with no difference in Ca(2+)-induced swelling between the two mitochondrial fractions. In the SSM fraction, no difference in the time course of swelling in Ca(2+)-free solution between CG and EG was detected. In the EG, both SSM and IFM fractions demonstrated a decreased sensitivity to Ca(2+); IFM fractions, however, exhibited significantly less pronounced swelling following Ca(2+) addition. The authors conclude that IFM and SSM fractions do not differ in their sensitivity to Ca(2+)-induced swelling. While dietary omega-3 PUFA protected both mitochondrial fractions against Ca(2+)-evoked swelling, the protective effect appeared to be more pronounced for the IFM fraction than for the SSM fraction.

Myocardial NOS activity and connexin-43 expression in untreated and omega-3 fatty acids-treated spontaneously hypertensive and hereditary hypertriglyceridemic rats.

The purpose of this study is to investigate myocardial nitric oxide synthase (NOS) activity and connexin-43 (Cx43) expression in young and old spontaneously hypertensive rats (SHR), adult hereditary hypertriglyceridemic (HTG) rats, and age-matched healthy rats without and with omega-3 PUFA supplementation for 2 months. Results showed that comparing to healthy rats the myocardial NOS activity was significantly increased in young SHR (8.2 ± 1.16 vs. 1.37 ± 0.67 pmol/min/mg) as well as old SHR (3.21 ± 0.75 vs. 2.22 ± 0.56 pmol/min/mg) and to much lesser extent in HTG rats, i.e., 1.87 ± 0.42 vs. 1.34 ± 0.1 pmol/min/mg. In parallel, there was a significant decline of total and phosphorylated forms of Cx43 in both groups of SHR while not in HTG rat hearts in which phosphorylated form of Cx43 was increased. Elevated NOS activity was suppressed (P < 0.05) in young and old SHR supplemented with omega-3 PUFA and it was associated with up-regulation of Cx43. In contrast to SHR, elevation of NOS activity in HTG rat hearts was not affected by treatment with omega-3 PUFA. However, increase of phosphorylated form of Cx43 was suppressed. In conclusion, there is an inverse relationship between myocardial NOS activity and Cx43 expression in SHR while not HTG rat hearts and omega-3 PUFA modulate both NOS activity and Cx43 expression. Whether over-expression of inducible NOS might account for down-regulation of myocardial Cx43 and whether its up-regulation is associated with an increase of endothelial NOS should be explored in further study.