Mangiferin Mitigates Gastric Ulcer in Ischemia/ Reperfused Rats: Involvement of PPAR-γ, NF-κB and Nrf2/HO-1 Signaling Pathways

Mangiferin protects against ‭intestinal ischemia/reperfusion-induced ‭liver injury: ‬‬Involvement of PPAR-‭γ, GSK-3β and Wnt/β-catenin pathway‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬

AIM

Mangiferin (MF), a xanthonoid from Mangifera indica, possesses anti-inflammatory, immunomodulatory, and potent antioxidant effects; however, its protective effect against mesenteric ischemia/reperfusion (I/R)-induced liver injury has not been fully clarified. The study was designed to assess the possible mechanism of action of MF against mesenteric I/R model.

MAIN METHODS

Male Wister rats were treated with MF (20mg/kg, i.p) or the vehicle for 3 days before I/R, which was induced by clamping the superior mesenteric artery for 30min followed by declamping for 60min.

KEY FINDINGS

The mechanistic studies revealed that MF protected the 2 organs studied, viz., liver and intestine partly via increasing the content of β-catenin and PPAR-γ along with decreasing that of GSK-3β and the phosphorylated NF-қB-p65. MF antioxidant effect was evidenced by increasing contents of total antioxidant capacity and GST, besides normalizing that of MDA. Regarding the anti-inflammatory effect, MF reduced IL-1β and IL-6, effects that were mirrored on the tissue content of MPO. Moreover, MF possessed anti-apoptotic character evidenced by elevating Bcl-2 content and reducing that of caspase-3. In the serum, intestinal I/R increased the activity of ALT, AST, and creatine kinase.

SIGNIFICANCE

The intimated protective mechanisms of MF against mesenteric I/R are mediated, partially, by modulation of oxidative stress, inflammation, and apoptosis possibly via the involvement of Wnt/β-catenin/NF-қβ/ PPAR-γ signaling pathways.

Diosmetin protects against ischemia/reperfusion-induced acute kidney injury in mice

BACKGROUND

Renal ischemia/reperfusion (I/R)-induced acute kidney injury remains to be a troublesome condition in clinical practice. Although the exact molecular mechanisms underlying renal I/R injury are incompletely understood, the deleterious progress of renal I/R injury involves inflammation, apoptosis, and oxidative stress. Diosmetin is a member of the flavonoid glycosides family, which suppresses the inflammatory response and cellular apoptosis and enhances antioxidant activity. The purpose of this study was to investigate the protective effect of diosmetin on I/R-induced renal injury in mice.

METHODS

Thirty BALB/c mice were randomly divided into five groups. Four groups of mice received diosmetin (0.25, 0.5, and 1 mg/kg) or vehicle (I/R group) before ischemia. Another group received vehicle without ischemia to serve as a negative control (sham-operated group). Twenty-four hours after reperfusion, serum and renal tissues were harvested to evaluate renal function and histopathologic features. In addition, the expression of inflammation-related proteins, apoptotic molecules, and antioxidant enzymes was analyzed.

RESULTS

Compared with sham mice, the I/R group significantly exacerbated renal function and renal tube architecture and increased the inflammatory response and renal tubule apoptosis. Nevertheless, pretreatment with diosmetin reversed these changes. In addition, diosmetin treatment resulted in a marked increase in antioxidant protein expression compared with I/R mice.

CONCLUSIONS

The renoprotective effects of diosmetin involved suppression of the nuclear factor-κB and mitochondrial apoptosis pathways, as well as activation of the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 pathway. Diosmetin has significant potential as a therapeutic intervention to ameliorate renal injury after renal I/R.

Minocycline attenuates sevoflurane-induced cell injury via activation of Nrf2

Minocycline has been demonstrated to exert neuroprotective effects in various experimental models. In the present study, we investigated the mechanisms underlying the protective effects of minocycline on cell injury induced by the inhalation of the anesthetic, sevoflurane. In our in vivo experiments using rats, minocycline attenuated sevoflurane-induced neuronal degeneration and apoptosis in the rat hippocampus, and this effect was associated with the minocycline-mediated suppression of oxidative stress in the hippocampus. In in vitro experiments, minocycline inhibited sevoflurane-induced apoptosis and the production of reactive oxygen species (ROS) in H4 human neuroglioma cells. In addition, minocycline suppressed the sevoflurane-induced upregulation of interleukin (IL)-6 and the activation of the nuclear factor-κB (NF-κB) signaling pathway in H4 cells. Furthermore, we found that nuclear factor E2-related factor 2 (Nrf2), an activator of the stress response, was upregulated and activated upon sevoflurane treatment both in the rat hippocampus and in H4 cells. In addition, minocycline further augmented the upregulation and activation of Nrf2 when used in conjunction with sevoflurane. Moreover, the knockdown of Nrf2 in H4 cells by small interfering RNA (siRNA) diminished the cytoprotective effect of minocycline, and attenuated the inhibitory effect of minocycline on ROS production, IL-6 upregulation and the activation of the NF-κB signaling pathway. On the whole, our findings indicate that minocycline may exert protective effects against sevoflurane-induced cell injury via the Nrf2-modulated antioxidant response and the inhibition of the activation of the NF-κB signaling pathway.

Mangiferin from Pueraria tuberosa reduces inflammation via inactivation of NLRP3 inflammasome

Recent reports have demonstrated the role of phyto-constituents in modulating inflammatory responses. Mangiferin isolated from Mangifera indica is known to induce potent anti-oxidative, anti-diabetic and anti-inflammatory activity. However, the molecular mechanism of its anti-inflammatory activity is not properly understood. In this study we have isolated Mangiferin from the tubers of Pueraria tuberosa (PT-Mangiferin) and analysed the mechanism of its potent anti-inflammatory effects in LPS stimulated RAW 264.7 mouse macrophage cell line and in a carrageenan induced air pouch model. PT-Mangiferin was non-toxic to primary cells but showed significant toxicity and apoptotic effect on cancerous cells. It significantly reduced the production of pro-inflammatory mediators (COX-2, iNOS and TNF-α) in LPS stimulated RAW 264.7 cells. Further, it has also reduced the generation of ROS and inhibited LPS induced NF-kB translocation in these cells. Additionally, PT-Mangiferin significantly reduced inflammation in a mouse air pouch model by inhibiting the infiltration of monocytes and neutrophils and reducing the production of cytokines. These effects were mediated via inactivation of NLRP3 inflammasome complex and its downstream signalling molecules. Taken together these results suggest that PT-Mangiferin is potent anti-inflammatory compound that reduces inflammation and holds promise in development of herbal based anti-inflammatory therapeutics in future.

Phytochemicals enhance antioxidant enzyme expression to protect against NSAID-induced oxidative damage of the gastrointestinal mucosa

The gastrointestinal (GI) mucosa provides the first protective barrier for digested food and xenobiotics, which are easily attacked by toxic substances. Nonsteroidal anti-inflammatory drugs, including aspirin, diclofenac, indomethacin, and ketoprofen, are widely used in clinical medicine, but these drugs may cause oxidative stress, leading to GI damage such as ulcers. Lansoprazol, omeprazole, and other clinical drugs are widely used to treat duodenal and gastric ulcers and have been shown to have multiple biological functions, such as antioxidant activity and the ability to upregulate antioxidant enzymes in vivo. Therefore, the reduction of oxidative stress may be an effective curative strategy for preventing and treating nonsteroidal anti-inflammatory drug induced ulcers of the GI mucosa. Phytochemicals, such as dietary phenolic compounds, phenolic acids, flavan-3-ols, flavonols, flavonoids, gingerols, carotenes, and organosulfur, are common antioxidants in fruits, vegetables, and beverages. A large amount of evidence has demonstrated that natural phytochemicals possess bioactivity and potential health benefits, such as antioxidant, anti-inflammatory, and antibacterial benefits, and they can prevent digestive disease processes. In this review, we summarize the literature on phytochemicals with biological effects, such as angiogenic, antioxidant, antiapoptotic, anti-inflammatory, and antiulceration effects, and their related mechanisms are also discussed.

Toll-like receptor 4 protects against stress-induced ulcers via regulation of glucocorticoid production in mice

Stress-induced gastric ulcer is an important life-threatening condition, while the molecular basis of its development is incompletely understood. Toll-like receptor 4 (TLR4), an innate immune pattern recognition receptor, can induce pro-inflammatory transcription, aggravating a stress ulcer. The present study found that TLR4 played a protective role in a mouse model of water immersion (23 °C) restraint stress. Wild-type (WT) and TLR4^-/- male mice were respectively divided into five groups (5 per group), and exposed to the stressor for 0, 0.5, 1, 2, or 4 hours. Gastric ulcer index, determined post mortem, increased with time in both types of mice but was greater in TLR4^-/- mice. Furthermore, increased serum cortisol and corticosterone concentrations were observed in WT mice only, and such increases were detected only in WT mice 4 h after lipopolysaccharide (LPS) treatment (2 mg/kg, intraperitoneal injection). Moreover, the administration of cortisol alleviated the gastric injury in TLR4^-/- mice. Western blotting showed expression in the adrenal of P450scc (CYP11A1), the first rate-limiting enzyme in the synthesis of steroids, was increased 4 h after water immersion restraint stress or LPS treatment in WT mice, but was conversely decreased in TLR4^-/- mice after either stressor. Furthermore, in adrenal glands of TLR4^-/- mice, structural distortion of mitochondria (which contain CYP11A1) was found with electron microscopy, and lack of lipid-storing droplets was found using light microscopy on adrenal cryosections stained with Oil red O. These data indicate that TLR4 plays a protective role in stress-induced gastric ulcer that is exerted via impacting synthesis of glucocorticoid in the adrenal gland.

Bufei Yishen granules combined with acupoint sticking therapy suppress oxidative stress in chronic obstructive pulmonary disease rats: Via regulating peroxisome proliferator-activated receptor-gamma signaling

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine (TCM) is clinically used under the guidance of its unique theory system. Bufei Yishen (BY) granules, an oral Chinese herbal formula, is confirmed effective for treating the syndrome of lung-kidney qi deficiency in chronic obstructive pulmonary disease (COPD) patients. Shu-Fei Tie ointment is another prescription for acupoint sticking (AS) therapy based on the theory of treating an internal disease by external treatment on proper acupoints. The beneficial effects of BY granules combined with Shu-Fei Tie have been proved in previous clinical trials. However, the underlying mechanism remains unclear. The present study was initiated to explore the antioxidative mechanism of the integrated therapy of BY granules and acupoint sticking via regulating by peroxisome proliferator activated receptor-gamma (PPARγ) signaling in a cigarette-smoke/bacterial exposure induced COPD rat model.

MATERIALS AND METHODS

Rats were randomized into Control, Model, BY, AS, BY+AS and aminophylline (APL) groups. COPD rats were induced by cigarette-smoke and bacterial exposures, and were administrated with normal saline, BY granules, AS, BY+AS or aminophylline from week 9 and sacrificed at week 20. Activity of superoxide dismutase (SOD) and levels of methane dicarboxylic aldehyde (MDA) in peripheral blood and bronchoalveolar lavage fluid (BALF) were determined by hydroxylamine and thiobarbituric acid methods. The gene and protein expressions of PPARγ in the lung tissues were analyzed by quantitative polymerase chain reaction and western blot.

RESULTS

Serum and BALF SOD decreased significantly in Model group (P<0.01), while MDA increased (P<0.01). Compared to COPD rats, serum SOD was higher in all treatment groups (P<0.01), and BALF SOD was higher in BY and BY+AS groups (P<0.01); serum and BALF MDA was lower in all treatment groups (P<0.01). Serum and BALF SOD was higher in BY+AS group than in AS group, while MDA was lower (P<0.05). BALF SOD increased in BY+AS group compared with APL group, while MDA decreased (P<0.05). PPARγ mRNA and protein and the phosphorylation of PPARγ (p-PPARγ) decreased in COPD rats (P<0.01), and increased in all treatment groups (P<0.01). PPARγ mRNA was higher in BY+AS group than in AS group (P<0.05), PPARγ and p-PPARγ were higher in BY+AS group than in AS and APL groups (P<0.05, P<0.01); PPARγ protein was higher in BY group than in APL group (P<0.05).

CONCLUSION

Bufei Yishen granules, Shu-Fei Tie and their combination have beneficial effects in stable COPD, and can attenuate the oxidative stress, and the activation of PPARγ signaling might be involved in the underlying mechanisms, but there are no obvious synergistic effect of Bufei Yishen granules and Shu-Fei Tie.

Omeprazole induces heme oxygenase-1 in fetal human pulmonary microvascular endothelial cells via hydrogen peroxide-independent Nrf2 signaling pathway

Omeprazole (OM) is an aryl hydrocarbon receptor (AhR) agonist and a proton pump inhibitor that is used to treat humans with gastric acid related disorders. Recently, we showed that OM induces NAD (P) H quinone oxidoreductase-1 (NQO1) via nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent mechanism. Heme oxygenase-1 (HO-1) is another cytoprotective and antioxidant enzyme that is regulated by Nrf2. Whether OM induces HO-1 in fetal human pulmonary microvascular endothelial cells (HPMEC) is unknown. Therefore, we tested the hypothesis that OM will induce HO-1 expression via Nrf2 in HPMEC. OM induced HO-1 mRNA and protein expression in a dose-dependent manner. siRNA-mediated knockdown of AhR failed to abrogate, whereas knockdown of Nrf2 abrogated HO-1 induction by OM. To identify the underlying molecular mechanisms, we determined the effects of OM on cellular hydrogen peroxide (H2O2) levels since oxidative stress mediated by the latter is known to activate Nrf2. Interestingly, the concentration at which OM induced HO-1 also increased H2O2 levels. Furthermore, H2O2 independently augmented HO-1 expression. Although N-acetyl cysteine (NAC) significantly decreased H2O2 levels in OM-treated cells, we observed that OM further increased HO-1 mRNA and protein expression in NAC-pretreated compared to vehicle-pretreated cells, suggesting that OM induces HO-1 via H2O2-independent mechanisms. In conclusion, we provide evidence that OM transcriptionally induces HO-1 via AhR - and H2O2 - independent, but Nrf2 - dependent mechanisms. These results have important implications for human disorders where Nrf2 and HO-1 play a beneficial role.

Dioscin attenuates gastric ischemia/reperfusion injury through the down-regulation of PKC/ERK1/2 signaling via PKCα and PKCβ2 inhibition

BACKGROUND

We previously reported the promising effects of dioscin against cerebral and renal ischemia-reperfusion (I/R) injury. However, its role against gastric I/R injury has not yet been reported. Thus, the aim of the present work was to investigate the protective effect and possible mechanisms of dioscin against gastric I/R.

MATERIALS AND METHODS

The hypoxia-reoxygenation (H/R) model in GES-1 cells and the celiac artery occlusion model in rats were carried out in the study.

RESULTS

Dioscin markedly attenuated H/R insult in GES-1 cells and gastric I/R injury in rats. Mechanistic studies demonstrated that dioscin-induced gastric protection was accompanied by inhibiting the levels of PKCα, PKCβ2 and phosphorylation via decreasing Raf-1 level. Blockade of PKC/ERK1/2 signaling pathway by dioscin decreased MEK1/2 level, ERK1/2 phosphorylation and the nuclear translocation, NF-κB and AP-1 transcriptional activities, pro-inflammatory cytokine responses, and up-regulated PPAR-γ level. Moreover, the results of small interfering RNA (siRNA) and overexpression of PKCα and PKCβ2 confirmed that dioscin attenuated gastric I/R injury through inhibiting PKC/ERK1/2 signaling by down-regulating PKCα and PKCβ2.

CONCLUSION

These data confirmed the protective effect of dioscin against gastric I/R injury, which should be developed as a therapeutic agent for the treatment of acute gastric mucosal lesions in the future.

Nuclear factor erythroid 2-related factor 2 antibody attenuates thermal hyperalgesia in the dorsal root ganglion: Neurochemical changes and behavioral studies after sciatic nerve-pinch injury

Oxidative stress is generated in several peripheral nerve injury models.Nuclear factor erythroid 2-related factor 2 (Nrf2) is activated to have a role in antioxidant effect. After nerve injury, the severely painful behavior is also performed. However, little has been explored regarding the function of Nrf2 in this painful process. Therefore, in this study, we compared the effects of Nrf2 antibody administration following sciatic nerve-pinch injury on painful behavior induced in young mice and neurochemical changes in dorsal root ganglion neurons. After pinch nerve injury, we found that the magnitude of the thermal allodynia was significantly decreased after application of Nrf2 antibody (5ul, 1mg/ml) in such injured animals and phosphorylated ERK(p-ERK) as well as the apoptotic protein (i.e., Bcl-6) in DRG neurons were also down-regulated in the anti-Nrf2-treated injured groups compared to the saline-treated groups. Taken collectively, these data suggested that the Nrf2 antibody reduced thermal hyperalgesia via ERK pathway and the down regulation of Bcl-6 protein from the apoptosis pathway might be protecting against the protein deletions caused by anti-Nrf2 effect and suggested the new therapeutic strategy with Nrf2 inhibitor following nerve injury.

Mangiferin and Cancer: Mechanisms of Action

Mangiferin, a bioactive compound derived primarily from Anacardiaceae and Gentianaceae families and found in mangoes and honeybush tea, has been extensively studied for its therapeutic properties. Mangiferin has shown promising chemotherapeutic and chemopreventative potential. This review focuses on the effect of mangiferin on: (1) inflammation, with respect to NFκB, PPARү and the immune system; (2) cell cycle, the MAPK pathway G₂/M checkpoint; (3) proliferation and metastasis, and implications on β-catenin, MMPs, EMT, angiogenesis and tumour volume; (4) apoptosis, with a focus on Bax/Bcl ratios, intrinsic/extrinsic apoptotic pathways and telomerase activity; (5) oxidative stress, through Nrf2/ARE signalling, ROS elimination and catalase activity; and (6) efficacy of chemotherapeutic agents, such as oxaliplatin, etoposide and doxorubicin. In addition, the need to enhance the bioavailability and delivery of mangiferin are briefly addressed, as well as the potential for toxicity.

Melatonin Prevents Mitochondrial Damage Induced by Doxorubicin in Mouse Fibroblasts Through Ampk-Ppar Gamma-Dependent Mechanisms

BACKGROUND Doxorubicin (brand name: Adriamycin®) is used to treat solid tissue cancer but it also affects noncancerous tissues. Its mechanism of cytotoxicity is probably related to increased oxidation, mitochondrial dysfunction, and apoptosis. Melatonin is reported to have antiapoptotic and antioxidative effects. The aim of this study was to determine whether melatonin would counteract in vitro cytotoxicity of doxorubicin in mouse fibroblasts and determine the pathway of its action against doxorubicin-induced apoptosis. MATERIAL AND METHODS We measured markers of apoptosis (cytochrome-c, mitochondrial membrane potential, and apoptotic cell number) and oxidative stress (total oxidant and antioxidant status) and calculated oxidant stress index in 4 groups of fibroblasts: controls, melatonin-treated, doxorubicin-treated, and fibroblasts concomittantly treated with a combination of melatonin and doxorubicin. RESULTS Melatonin given with doxorubicin succesfully countered apoptosis generated by doxorubicin alone, which points to its potential as a protective agent against cell death in doxorubicin chemotherapy. This also implies that patients should be receiving doxorubicin treatment when their physiological level of melatonin is at its highest, which is early in the morning. CONCLUSIONS This physiological level may not be high enough to overcome doxorubicin-induced oxidative stress, but adjuvant melatonin treatment may improve quality of life. Further research is needed to verify our findings.

Omeprazole induces NAD(P)H quinone oxidoreductase 1 via aryl hydrocarbon receptor-independent mechanisms: Role of the transcription factor nuclear factor erythroid 2-related factor 2

Activation of the aryl hydrocarbon receptor (AhR) transcriptionally induces phase I (cytochrome P450 (CYP) 1A1) and phase II (NAD(P)H quinone oxidoreductase 1 (NQO1) detoxifying enzymes. The effects of the classical and nonclassical AhR ligands on phase I and II enzymes are well studied in human hepatocytes. Additionally, we observed that the proton pump inhibitor, omeprazole (OM), transcriptionally induces CYP1A1 in the human adenocarcinoma cell line, H441 cells via AhR. Whether OM activates AhR and induces the phase II enzyme, NAD(P)H quinone oxidoreductase 1 (NQO1), in fetal primary human pulmonary microvascular endothelial cells (HPMEC) is unknown. Therefore, we tested the hypothesis that OM will induce NQO1 in HPMEC via the AhR. The concentrations of OM used in our experiments did not result in cytotoxicity. OM activated AhR as evident by increased CYP1A1 mRNA expression. However, contrary to our hypothesis, OM increased NQO1 mRNA and protein via an AhR-independent mechanism as AhR knockdown failed to abrogate OM-mediated increase in NQO1 expression. Interestingly, OM activated Nrf2 as evident by increased phosphoNrf2 (S40) expression in OM-treated compared to vehicle-treated cells. Furthermore, Nrf2 knockdown abrogated OM-mediated increase in NQO1 expression. In conclusion, we provide evidence that OM induces NQO1 via AhR-independent, but Nrf2-dependent mechanisms.