Protective effect of thymoquinone improves cardiovascular function, and attenuates oxidative stress, inflammation and apoptosis by mediating the PI3K/Akt pathway in diabetic rats

Protective effect of thymoquinone nanoemulsion in reducing the cardiotoxic effect of 5-fluorouracil in rats

5-Fluorouracil (5-FU), which is one of the most widely used chemotherapy drugs, has various side effects on the heart. Thymoquinone (TMQ), the main bioactive component of Nigella sativa, has antioxidant and protective effects against toxicity. In this study, we investigated the protective effect of thymoquinone against cardiotoxicity caused by 5-FU in vitro and in vivo models. H9C2 cells were exposed to 5-FU and TMQ, and cell viability was evaluated in their presence. Also, 25 male Wistar rats were divided into five control groups, 5-FU, 2.5, and 5 mg TMQ in nanoemulsion form (NTMQ) + 5-FU and 5 mg NTMQ. Cardiotoxicity was assessed through electrocardiography, cardiac enzymes, oxidative stress markers, and histopathology. 5-FU induced cytotoxicity in H9c2 cells, which improved dose-dependently with NTMQ cotreatment. 5-FU caused body weight loss, ECG changes (increased ST segment, prolonged QRS, and QTc), increased cardiac enzymes (aspartate aminotransferase [AST], creatine kinase-myocardial band [CK-MB], and lactate dehydrogenase [LDH]), oxidative stress (increased malondialdehyde, myeloperoxidase, nitric acid; decreased glutathione peroxidase enzyme activity), and histological damage such as necrosis, hyperemia, and tissue hyalinization in rats. NTMQ ameliorated these 5-FU-induced effects. Higher NTMQ dose showed greater protective effects. Thus, the results of our study indicate that NTMQ protects against 5-FU cardiotoxicity likely through antioxidant mechanisms. TMQ warrants further research as an adjuvant to alleviate 5-FU chemotherapy side effects.

Potential Pharmacological Applications of Nigella Seeds with a Focus on Nigella sativa and Its Constituents against Chronic Inflammatory Diseases: Progress and Future Opportunities

The leading cause of death worldwide has been identified as chronic illnesses, according to the World Health Organization (WHO). Chronic inflammatory conditions such as asthma, cancer, diabetes, heart disease, and obesity account for three out of every five deaths. Although many people benefit from using nonsteroidal anti-inflammatory medicines (NSAIDs) for pain and inflammation relief, there are significant adverse effects to using these medications. Medicinal plants possess anti-inflammatory properties with minimal or no side effects. Nigella sativa (NS), also known as black cumin, is one of the plants used in traditional medicine the most. Many studies on the NS have shown that their therapeutic properties are attributed to the seed, oil, and secondary metabolites. This plant has been studied extensively and has many medical uses, such as anti-inflammatory. NS or its phytochemical compounds, such as thymoquinone, can cause cell apoptosis via oxidative stress, block efflux pumps, enhance membrane permeability, and exert potent biocidal effects. Notwithstanding the extensively documented anti-inflammatory effectiveness observed in the experimental model, the precise mechanisms underlying its anti-inflammatory effects in diverse chronic inflammatory diseases and its multi-targeting characteristics remain largely unexplored. This review examines NS or its secondary metabolites, a valuable source for the therapeutic development of chronic inflammatory diseases. Most clinical studies were done for diabetes and cardiovascular disease; therefore, more studies are required to examine the NS extracts and phytoconstituents to treat cancer, obesity, diabetes, asthma, neurological disorders, and COVID-19. This study will be a significant resource for clinicians and biologists seeking a pharmaceutical solution for inflammatory diseases.

Molecular mechanisms and signaling pathways of black cumin (Nigella sativa) and its active constituent, thymoquinone: a review

BACKGROUND

Nigella sativa and its main bioactive ingredient, thymoquinone, exhibit various pharmacological activities, including neuroprotective, nephroprotective, cardioprotective, gastroprotective, hepatoprotective, and anti-cancer effects. Many studies have been conducted trying to elucidate the molecular signaling pathways that mediate these diverse pharmacological properties of N. sativa and thymoquinone. Accordingly, the goal of this review is to show the effects of N. sativa and thymoquinone on different cell signaling pathways.

METHODS

The online databases Scopus, PubMed and Web of Science were searched to identify relevant articles using a list of related keywords such as Nigella sativa, black cumin, thymoquinone, black seed, signal transduction, cell signaling, antioxidant, Nrf2, NF-κB, PI3K/AKT, apoptosis, JAK/STAT, AMPK, MAPK, etc. Only articles published in the English language until May 2022 were included in the present review article.

RESULTS

Studies indicate that N. sativa and thymoquinone improve antioxidant enzyme activities, effectively scavenges free radicals, and thus protect cells from oxidative stress. They can also regulate responses to oxidative stress and inflammation via Nrf2 and NF-κB pathways. N. sativa and thymoquinone can inhibit cancer cell proliferation through disruption of the PI3K/AKT pathway by upregulating phosphatase and tensin homolog. Thymoquinone can modulate reactive oxygen species levels in tumor cells, arrest the cell cycle in the G2/M phase as well as affect molecular targets including p53, STAT3 and trigger the mitochondrial apoptosis pathway. Thymoquinone, by adjusting AMPK, can regulate cellular metabolism and energy hemostasis. Finally, N. sativa and thymoquinone can elevate brain GABA content, and thus it may ameliorate epilepsy.

CONCLUSIONS

Taken together, the improvement of antioxidant status and prevention of inflammatory process by modulating the Nrf2 and NF-κB signaling and inhibition of cancer cell proliferation through disruption of the PI3K/AKT pathway appear to be the main mechanisms involved in different pharmacological properties of N. sativa and thymoquinone.

Effects of Thymoquinone Alone or in Combination with Losartan on the Cardiotoxicity Caused by Oxidative Stress and Inflammation in Hypercholesterolemia

Dietary cholesterol accelerates oxidative and pro-inflammatory processes, causing hypercholesterolemia and cardiovascular diseases. Thus, the purpose of the current study is to compare the protective effects of thymoquinone (TQ) alone or in combination with losartan (LT) against the heart damage caused by a high-cholesterol diet (HCD). HCD-fed rat groups revealed an elevated activity of indicators of cardiac enzymes in the serum. Serum and cardiac lipids were also found to be significantly higher in HCD-fed rat groups. Cardiac pro-inflammatory and oxidative markers were also increased in HCD-fed rat groups, whereas antioxidant indicators were decreased. However, all of these biochemical, inflammatory, antioxidant, and oxidative change indicators returned to levels similar to those of normal rats after treatment with TQ alone or in combination with LT administered to HCD-fed rat groups. Hypercholesterolemia considerably induced the lipid peroxidation product, thiobarbituric acid reaction substances (TBARs), and oxidative radicals in cardiac cells, which were attenuated by QT and LT treatments, particularly when combined. Finally, QT, LT, and their combination were able to reduce the histological changes changes brought on by cholesterol excess in cardiac tissues. In conclusion, administration of TQ in a combination with LT which has a better protective effect, significantly reduced the hypercholesterolemic-induced oxidative and inflammatory changes that occurred in cardiac tissue.

The effects of thymoquinone on pancreatic cancer: Evidence from preclinical studies

Thymoquinone (TQ) is a secondary metabolite found in abundance in very few plant species including Nigella sativa L., Monarda fistulosa L., Thymus vulgaris L. and Satureja montana L. Preclinical pharmacological studies have shown that TQ has many biological activities, such as anti-inflammatory, antioxidant and anticancer. Both in vivo and in vitro experiments have shown that TQ acts as an antitumor agent by altering cell cycle progression, inhibiting cell proliferation, stimulating apoptosis, inhibiting angiogenesis, reducing metastasis and affecting autophagy. In this comprehensive study, the evidence on the pharmacological potential of TQ on pancreatic cancer is reviewed. The positive results of preclinical studies support the view that TQ can be considered as an additional therapeutic agent against pancreatic cancer. The possibilities of success for this compound in human medicine should be further explored through clinical trials.

Thymoquinone improved redox homeostasis in the heart and aorta of hypothyroid rats

OBJECTIVES

Propylthiouracil (PTU) is a common drug that is used in medicine for treating hyperthyroidism. Furthermore, hypothyroidism can also be induced with PTU. Considering the antioxidant effects of thymoquinone (TMQ), this study was designed to find out whether TMQ could counteract the oxidative damage in the heart and aorta tissues induced by hypothyroidism in rats.

METHODS

Animals were arranged into four groups: (1) Control, (2) PTU, (3) PTU-TMQ 5, and (4) PTU-TMQ 10. Hypothyroidism was induced in rats by giving 0.05% PTU in drinking water. PTU and TMQ (5 and 10 mg/kg, ip) treatments were done for 42 days. Finally, the animals were sacrificed and the serum of the rats was collected for thyroxine level assessment. The heart and aorta tissues were also removed for biochemical oxidative stress markers measurement.

RESULTS

A lower serum thyroxine level was observed after PTU treatment compared to the control group. Hypothyroidism also was accompanied by a decrease of thiol content, and superoxide dismutase (SOD), and catalase (CAT) activities in the heart and aorta tissues while increased malondialdehyde (MDA). Furthermore, a significant reduction in oxidative damage was noted in the heart and aorta following the administration of TMQ (5 and 10 mg/kg) which was indicated by the reduction in MDA and improved activities of SOD, CAT, and thiol.

CONCLUSION

In this study, TMQ was found to improve oxidative damages in the heart and aorta tissues of hypothyroid rats.

Cardioprotective Effect of Gynostemma pentaphyllum against Streptozotocin Induced Cardiac Toxicity in Rats via Alteration of AMPK/Nrf2/HO-1 Pathway

Gynostemma pentaphyllum (GP) is a plant commonly used in diabetic therapy in China. GP having potent antioxidant effect against various free radicals. The purpose of the current investigation to identify the cardioprotective effect of GP against streptozotocin (STZ)/ high fat diet (HFD) induced cardiac dysfunction in rats via alteration of AMPK/Nrf2/HO-1 pathway. Wistar rats were used for the current protocol. The rats were received the intraperitoneal injection of STZ and HFD to induce the cardiac remodelling. Blood glucose level, insulin and lipid parameters were estimated. Blood pressure and heart rate were also estimated. Cardiac parameters, antioxidant, cytokines, total protein and inflammatory mediators were analysed. The mRNA expression was detected using the RT-qPCR, respectively. GP significantly (p < 0.001) decreased the BGL and improved the insulin level. GP altered the ratio of heart/BW, liver/BW, and lung/BW. GP treatment significantly (p < 0.001) suppressed the heart rate and blood pressure (diastolic, systolic and mean pressure). GP significantly (p < 0.001) reduced the level of TC, LDL, TG, VLDL and increased the level of HDL. DCM induced rats received the GP administration exhibited reduction in the level of CK and LDH. GP significantly (p < 0.001) reduced the levels of MDA, hydrogen peroxide, peroxynitrite, ROS and increased the level of GSH, SOD, CAT and GPx. GP significantly (p < 0.001) reduced the levels of cytokines (TNF-α, IL-6, IL-1β) and inflammatory parameters (COX-2 and NFκB). GP significantly (p < 0.001) suppressed the NLRP3 and NF-κB expression. GP also boosted mitochondrial biogenesis by boosting the PGC-1α, HO-1 and Nrf2 expression in cardiac tissue. GP treatment showed the cardioprotective effects against STZ induced diabetic cardiac dysfunction via alteration of AMPK/Nrf2/HO-1 pathway.

Protective Effect of Curcumin, Chrysin and Thymoquinone Injection on Trastuzumab-Induced Cardiotoxicity via Mitochondrial Protection

Mitochondrial dysfunction may lead to cardiomyocyte death in trastuzumab (TZM)-induced cardiotoxicity. Accordingly, this study was designed to evaluate the mitochondrial protective effects of curcumin, chrysin and thymoquinone alone in TZM-induced cardiotoxicity in the rats. Forty-eight male adult Wistar rats were divided into eight groups: control group (normal saline), TZM group (2.5 mg/kg I.P. injection, daily), TZM + curcumin group (10 mg/kg, I.P. injection, daily), TZM + chrysin (10 mg/kg, I.P. injection, daily), TZM + thymoquinone (0.5 mg/kg, I.P. injection, daily), curcumin group (10 mg/kg, I.P. injection, daily), chrysin group (10 mg/kg, I.P. injection, daily) and thymoquinone group (10 mg/kg, I.P. injection, daily). Blood and tissue were collected on day 11 and used for assessment of creatine phosphokinase, lactate dehydrogenase (LDH), troponin, malondialdehyde (MDA) amount, glutathione levels and mitochondrial toxicity parameters. TZM increased mitochondrial impairments (reactive oxygen species formation, mitochondrial swelling, mitochondrial membrane potential collapse and decline in succinate dehydrogenase activity) and histopathological alterations (hypertrophy, enlarged cell, disarrangement, myocytes degeneration, infiltration of fat in some areas, hemorrhage and focal vascular thrombosis) in rat heart. As well as TZM produced a significant increase in the level of CK, LDH, troponin, MDA, glutathione disulfide. In most experiments, the co-injection of curcumin, chrysin and thymoquinone with TZM restored the level of CK, LDH, troponin, MDA, GSH, mitochondrial impairments and histopathological alterations. The study revealed the cardioprotective effects of curcumin, chrysin and thymoquinone against TZM-induced cardiotoxicity which could be attributed to their antioxidant and mitochondrial protection activities.

Thymoquinone attenuates isoproterenol-induced myocardial infarction by inhibiting cytochrome C and matrix metalloproteinase-9 expression

Thymoquinone (TQ) is the main active constituent of Nigella sativa. The present study aimed to investigate the effect of TQ on apoptotic parameters and MMP-9 expression in isoproterenol (ISP)-induced myocardial infarction (MI). TQ was given once daily for 7 days at doses of 10 and 20 mg/kg orally with ISP (86 mg/kg; s.c.) administered on the sixth and seventh days. TQ pre-treatment protected against ISP-induced MI as approved by normalisation of electrocardiogram (ECG) and b (CK)-MB, minimal histopathological changes, and reduction of the infarction size. Effects of TQ could be supported by its antioxidant activity, evidenced by the increase of cardiac reduced glutathione and total serum antioxidant capacity, and the inhibition of ISO-induced lipid peroxidation. TQ anti-inflammatory activity was associated with reduced expression of NF-κB and TNF-α. TQ ameliorated cardiomyocytes^, apoptotic pathways by inhibiting both the intrinsic pathway, via reducing cytoplasmic cytochrome C, and the extrinsic pathway, by inhibiting TNF-α and caspases, and the effect of TQ was dose-dependent. Moreover, TQ reduced the expression of metalloproteinase (MMP)-9, which is considered as a prognostic marker of ventricular remodelling, recommending that TQ can be used as a possible supplement to minimise post-MI changes. So, we conclude that TQ antiapoptotic activity and the inhibitory modulation of MMP-9 expression contribute to TQ protective effects in MI. To our knowledge, this is the first study reporting the effect of TQ on cytochrome c activity and MMP-9 expression in MI.

Cardioprotective effects of co-administration of thymoquinone and ischemic postconditioning in diabetic rats

OBJECTIVES

Ischemia/reperfusion (I/R) is a leading cause of myocardial infarction (MI) injury, contributing to excess injury to cardiac tissues involved in inflammation, apoptosis, and oxidative stress. The present study was conducted to examine the effects of combined thymoquinone (TQ) with ischemic postconditioning (IPostC) therapy on apoptosis and inflammation due to I/R injury in diabetic rat hearts.

MATERIALS AND METHODS

A single dose injection of streptozotocin (STZ; 60 mg/kg) was administered to thirty-two Wistar male rats to induce diabetes. Hearts were fixed on a Langendorff setting and exposed to a 30 min regional ischemia subsequently to 60 min reperfusion. IPostC was induced at the onset of reperfusion by 3 cycles of 30 sec R/I. ELISA, Western blotting assay, and TUNEL staining were applied to assess the cardioprotective effect of IPostC and TQ against I/R injury in diabetic and non-diabetic rats.

RESULTS

Administration of TQ alone in non-diabetic isolated hearts significantly diminished CK-MB, TNF-α, IL-1β, and apoptosis and enhanced p-GSK-3β and Bcl-2 (P<0.05). Following administration of TQ, the cardioprotective effects of IPostC by elevating p-GSK-3β and Bcl-2 and alleviating apoptosis and inflammation were reestablished compared with non-IPostC diabetic hearts.

CONCLUSION

These results provide substantial evidence that co-administration of TQ plus IPostC can exert cardioprotective effects on diabetic myocardium during I/R damage by attenuating the inflammatory response and apoptosis.

Thymoquinone, a major constituent in Nigella sativa seeds, is a potential preventative and treatment option for atherosclerosis

Atherosclerosis is a widespread and progressive chronic arterial disease that remains the leading cause of mortality and morbidity worldwide. It is generally accepted that atherosclerosis is a multifactorial disease characterized by dyslipidemia and inflammation in the vessel walls. Nonpharmacological interventions to treat chronic diseases like atherosclerosis have gained considerable attention in recent years. Thymoquinone (TQ), the major bioactive constituent of Nigella sativa seeds, presents one such example of a natural therapeutic agent that has captured the attention of many researchers due to its wide array of medicinal properties, including its potent anti-atherosclerotic effects. Various in vitro and in vivo studies support the potential of TQ in ameliorating hyperlipidemia, hypercholesterolemia, oxidative stress, and inflammation, all of which are key hallmarks of atherosclerosis. However, to date, no review has been conducted to substantiate the role of TQ in preventing and/or treating atherosclerosis. This comprehensive review aims to examine recent in vitro and in vivo experimental findings reported on the potential anti-atherosclerotic effects of TQ. The roles of TQ in combatting hyperlipidemia, oxidative stress, and inflammation in atherosclerosis are highlighted. We also shed light on the role of TQ in preventing foam cell formation by decreasing low-density lipoprotein (LDL) availability and oxidation. Moreover, recent findings on the protective role of TQ on early markers of atherosclerosis, including homocysteinemia and endothelial dysfunction, are also underscored. Experimental evidence suggests that TQ can potentially be employed as a natural therapeutic agent with minimal side effects against the development and/or progression of atherosclerosis and its associated complications.

The ameliorative effects of thymoquinone and beta-aminoisobutyric acid on streptozotocin-induced diabetic cardiomyopathy

Diabetic cardiomyopathy (DCM) is a cardiac dysfunction observed in a patient with diabetes that may lead to heart failure. No specific treatment has yet been tested in DCM. Therefore, in this study, it was investigated that the potential of thymoquinone (TYM) and beta-aminoisobutyric acid (BAIBA) to treat DCM. Five groups (n = 7) were formed, namely control, diabetes, TYM, BAIBA and TYM + BAIBA, with a random selection from 35 adult male rats. Diabetes mellitus was induced by intraperitoneal administration of 50 mg/kg streptozotocin to all groups except the control. After establishing experimental diabetes, TYM (20 mg/kg/day) and BAIBA (100 mg/kg/day) were administered alone or in combination with other groups other than the control and diabetes groups for five weeks by gavage. Serum aspartate aminotransferase, lactate dehydrogenase, creatine kinase-MB, and tissue malondialdehyde levels increased significantly, and tissue glutathione levels decreased in the diabetes group compared to the control group. An increase in the expression of tumor necrosis factor-α in the myocardium and the rate of fibrosis and apoptosis were found in the histopathological analysis. In the TYM and BAIBA groups, all pathological changes observed in the diabetes group improved significantly. The therapeutic effects of these agents on DCM are probably due to their antihyperglycemic, antidiabetic, antioxidant, and anti-inflammatory effects. The present results suggested that TYM and BAIBA have the potential therapeutic effects on DCM that were used alone or combined.

Alleviation of prilocaine-induced epileptiform activity and cardiotoxicity by thymoquinone

PURPOSE

This study investigated whether thymoquinone (TQ) could alleviate central nervous system (CNS) and cardiovascular toxicity of prilocaine, a commonly used local anesthetic.

METHODS

Rats were randomized to the following groups: control, prilocaine treated, TQ treated and prilocaine + TQ treated. Electroencephalography and electrocardiography electrodes were placed and trachea was intubated. Mechanical ventilation was initiated, right femoral artery was cannulated for continuous blood pressure measurements and blood-gas sampling while the left femoral vein was cannulated for prilocaine infusion. Markers of myocardial injury, reactive oxygen/nitrogen species (ROS/RNS) generation and total antioxidant capacity (TAC) were assayed by standard kits. Aquaporin-4 (AQP4), nuclear factor(NF)κB-p65 and -p50 subunit in brain tissue were evaluated by histological scoring.

RESULTS

Blood pH and partial oxygen pressure, was significantly decreased after prilocaine infusion. The decrease in blood pH was alleviated in the prilocaine + TQ treated group. Prilocaine produced seizure activity, cardiac arrhythmia and asystole at significantly lower doses compared to prilocaine + TQ treated rats. Thymoquinone administration attenuated levels of myocardial injury induced by prilocaine. Prilocaine treatment caused increased ROS/RNS formation and decreased TAC in heart and brain tissue. Thymoquinone increased heart and brain TAC and decreased ROS/RNS formation in prilocaine treated rats. AQP4, NFκB-p65 and NFκB-p50 expressions were increased in cerebellum, cerebral cortex, choroid plexus and thalamic nucleus in prilocaine treated rats. Thymoquinone, decreased the expression of AQP4, NFκB-p65 and NFκB-p50 in brain tissue in prilocaine + TQ treated rats.

CONCLUSION

Results indicate that TQ could ameliorate prilocaine-induced CNS and cardiovascular toxicity.

Thymoquinone reduces mitochondrial damage and death of cardiomyocytes induced by clozapine

The generation of a reactive nitrenium ion by microsomal/mitochondrial cytochrome P450 (CYPs) from clozapine (CLZ) has been suggested as the main cause of cardiotoxicity by this drug. Previous studies indicated that thymoquinone (TQ) as an active constituent of Nigella sativa has pharmacological effects such as antioxidant, reactive oxygen species (ROS) scavenger, and inhibitory effect on CYPs enzymes. Therefore, we hypothesized that TQ with these pharmacological effects can reduce CLZ-induced toxicity in isolated cardiomyocytes and mitochondria. Rat left ventricular cardiomyocytes and mitochondria were isolated by collagenase perfusion and differential centrifugation respectively. Then, isolated cardiomyocytes and mitochondria were pretreated with different concentrations of TQ (1, 5, and 10 μmol/l) for 30 min and then followed by exposure to CLZ (50 μmol/l) for 6 h. After 6 h of incubation, using biochemical evaluations and flow cytometric analysis, the parameters of cellular toxicity including cytotoxicity, the level of oxidized/reduced glutathione (GSH/GSSG), malondialdehyde (MDA), reactive oxygen species (ROS) formation, lysosomal membrane integrity, mitochondria membrane potential (ΔΨm) collapse, and mitochondrial toxicity including succinate dehydrogenase (SDH) activity and mitochondrial swelling were analyzed. We observed a significant toxicity in isolated cardiomyocytes and mitochondria after exposure with CLZ which was related to ROS formation, oxidative stress, GSH depletion, lysosomal and mitochondrial damages, and mitochondrial dysfunction and swelling, while TQ pretreatment reverted the above toxic effect of CLZ on isolated cardiomyocytes and mitochondria. Our results indicate that TQ prevents and reverses CLZ-induced cytotoxicity and mitochondrial damages in isolated cardiomyocytes and mitochondria, providing an experimental basis for clinical treatment on CLZ-induced cardiotoxicity.

Anti-inflammatory effects of thymoquinone and its protective effects against several diseases

Thymoquinone (TQ, 2-methyl-5-isopropyl-1, 4-benzoquinone), a monoterpene molecule present in Nigella sativa L., has an anti-inflammatory, anti-oxidant, and anti-apoptotic properties in several disorders such as asthma, hypertension, diabetes, inflammation, bronchitis, headache, eczema, fever, dizziness and influenza. TQ exerts its anti-inflammatory and anti-oxidant effects via several molecular pathways, including the release of cytokines, and activation of cyclooxygenase-2 (COX2), nuclear factor erythroid 2-related factor 2 (Nrf2), phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT), nuclear factor kappa-light-chain-enhancer of activated B (NF-Κβ). In this review, recent reports on the anti-inflammatory efficacy of TQ in heart disorders, respiratory diseases, neuroinflammation, diabetes and arthritis are summarized. We suggest that further investigation is necessary to better characterize the efficacy of TQ as a therapeutic agent.

Alleviative effects of 20(R)-Rg3 on HFD/STZ-induced diabetic nephropathy via MAPK/NF-κB signaling pathways in C57BL/6 mice

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic nephropathy (DN) is a major complication of diabetes. The kidney disease develops in nearly 20%-40% of type 2 diabetes (T2D) patients. Ginseng is the root of Panax ginseng C. A. Meyer and has been used in prevention and treatment of diseases for more than 2000 years as a traditional oriental medicine. The 20(R)-ginsenoside Rg3, an active saponin isolated from ginseng, can prevent and treat many diseases. The object of this research was to explore the alleviative effects of 20(R)-Rg3 on DN in mice.

MATERIALS AND METHODS

The T2D animal model was induced by continuous access to a high fat diet (HFD) combined with a single injection of 100 mg/kg streptozotocin (STZ) in C57BL/6 mice. The mice were treated by oral gavage of the 20(R)-Rg3 (10, 20 mg/kg) for 8 weeks. Functional and histopathological analyses of the kidneys were then performed. Protein expression levels of MAPKs and NF-κB signal pathways in the kidney were evaluated by western blotting. The expressions of HO-1 and NF-κB in the kidney were measured by fluorescent labeling staining. Other assessments including fasting blood glucose (FBG) levels, blood lipids, oxidative indicators, and inflammatory factors were all performed.

RESULTS

Abnormally elevated FBG levels were observed in HFD/STZ mice, contributing significantly to the occurrence of DN. Simultaneously, HFD/STZ mice showed the rise of serum total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) levels, and the decrease in high density lipoprotein cholesterol (HDL-C). DN was evidenced by the overproduction of malondialdehyde (MDA), decreased levels of superoxide dismutase (SOD) and catalase (CAT) enzymatic activities, high levels of serum blood urea nitrogen (BUN) and creatinine (Cr). Simultaneously, the results of the immunofluorescence assay showed an increased expression level in NF-κB p65 while a decrease in antioxidant enzyme HO-1 was observed. Herein, 20(R)-Rg3 treatment for 8 weeks not only attenuated FBG levels and advanced glycation end products (AGEs) levels but also improved insulin (INS) level, blood lipids, oxidative stress, and renal function by regulating MAPKs and NF-κB signal pathways in DN mice.

CONCLUSION

Taken together, the findings from the present study explicitly confirmed that 20(R)-Rg3 exerted ameliorative effects on DN mice via improving anti-oxidative activity and reducing renal inflammation.

Effects of Nigella sativa oil and thymoquinone against bisphenol A-induced metabolic disorder in rats

The underlying mechanisms of bisphenol A (BPA)-induced metabolic disorder and the protective impact of Nigella sativa oil (NSO) and thymoquinone (TQ) against BPA-induced metabolic disorder were investigated. Rats were treated as follows: Control, BPA (10 mg/kg), TQ (2 mg/kg), NSO (84 μL/kg), BPA + TQ (0.5, 1, 2 mg/kg), and BPA + NSO (21, 42, 84 μL/kg). BPA was administered by gavage, while, TQ and NSO were injected intraperitoneally (daily, 54 days). The weight, blood pressure, serum parameters [glucose, lipid profile, hepatic enzymes, insulin, interlukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), leptin, adiponectin], malondialdehyde (MDA), glutathione (GSH) and insulin signaling pathways [insulin receptor substrate (p-IRS,IRS); kinase (p-Akt,Akt); glycogen synthase kinase (p-GS3K,GS3K)] were measured. BPA increased the blood pressure, MDA, lipid profile, hepatic enzymes, insulin, IL-6, TNF-α, and leptin, and decreased the GSH and phosphorylated forms of IRS, Akt, GS3K but did not alter weight, glucose, IRS, AKT, and GS3K in the liver. Administration of NSO or TQ with BPA reduced the blood pressure, liver level of MDA, lipid profile, hepatic enzymes, insulin, IL-6, TNF-α, leptin, and increased the liver level of GSH and p-IRS, p-AKT, p-GS3K. TQ and NSO are thought to be effective in controlling metabolic disorders induced by BPA.

Ketogenic Diet Ameliorates Cardiac Dysfunction via Balancing Mitochondrial Dynamics and Inhibiting Apoptosis in Type 2 Diabetic Mice

The ketogenic diet (KD) has been widely used in clinical studies and shown to hace an anti-diabetic effect, but the underlying mechanisms have not been fully elaborated. Our aim was to investigate the effects and the underling mechanisms of the KD on cardiac function in db/db mice. In the present study, db/db mice were subjected to a normal diet (ND) or KD. Fasting blood glucose, cardiac function and morphology, mitochondrial dynamics, oxidative stress, and apoptosis were measured 8 weeks post KD treatment. Compared with the ND, the KD improved glycemic control and protected against diabetic cardiomyopathy in db/db mice, and improved mitochondrial function, as well as reduced oxidative stress were observed in hearts. In addition, KD treatment exerted an anti-apoptotic effect in the heart of db/db mice. Further data showed that the PI3K/Akt pathway was involved in this protective effect. Our data demonstrated that KD treatment ameliorates cardiac dysfunction by inhibiting apoptosis via activating the PI3K-Akt pathway in type 2 diabetic mice, suggesting that the KD is a promising lifestyle intervention to protect against diabetic cardiomyopathy.

Thymoquinone Attenuates Cardiomyopathy in Streptozotocin-Treated Diabetic Rats

Diabetic cardiomyopathy is a diabetic complication due to oxidative stress injuries. This study examined the protecting influence of thymoquinone (TQ) on diabetes-caused cardiac complications. The intracellular means by which TQ works against diabetes-caused cardiac myopathy in rats is not completely understood. In this study, Wistar male rats (n = 60) were assigned into four groups: control, diabetic (diabetes induced by IP infusion of streptozotocin, 65 mg/kg), diabetic + TQ (diabetic rats given TQ (50 mg/kg) administered once per day by stomach gavage), and TQ (50 mg/kg) for 12 weeks. TQ supplementation appreciably recovered the cardiac parameters alongside significant declines in plasma nitric oxide concentrations and total superoxide dismutase (T.SOD) activities. Importantly, TQ downgraded expression of cardiac-inducible nitric oxide synthase in addition to significantly upregulating vascular endothelial growth factor and erythropoietin genes and nuclear factor-erythroid-2-related factor 2 (Nrf2) protein. TQ normalized plasma triacylglycerol and low-density lipoprotein-cholesterol and significantly improved the high-density lipoprotein-cholesterol levels. Additionally, TQ administration improved the antioxidant ability of cardiac tissue via significantly increased cardiac T.SOD and decreased cardiac malondialdehyde levels. Oral supplementation with TQ prevented diabetic-induced cardiomyopathy via its inhibitory effect on the E-selectin level, C-reactive protein, and interleukin-6. The TQ protecting effect on the heart tissue was shown by normalization of the plasma cardiac markers troponin I and creatine kinase. This experiment shows the aptitude of TQ to protect cardiac muscles against diabetic oxidative stress, mainly through upregulation of Nrf2, which defeated oxidative damage by improvement of the antioxidant power of cardiac muscle that consequently protected the cardiac muscles and alleviated the inflammatory process.

Thymoquinone activates MAPK pathway in hippocampus of streptozotocin-treated rat model

Streptozotocin (STZ), a glucosamine-nitrosourea compound, produces deficiencies in learning, memory, and cognitive functions when it was administered intracerebroventricularly (i.c.v). In molecular level, increase in neuroinflammation and oxidative stress in brain, and decrease in the number of surviving neurons are the outcomes of STZ administration. Herein, we aimed to investigate the effect of thymoquinone (TQ), an anti-inflammatory, immunomodulatory and neuroprotective agent, on STZ-induced neurodegeneration in rats. For this purpose, bilateral i.c.v. injection of STZ (3 mg/kg) was given to adult female rats on days 1 and 3. TQ (20 mg/kg/day in cornoil) was administered intragastrically to rats for 15 days starting from the 15th day of STZ injection. The Morris water maze test and passive avoidance test were applied to measure the learning and memory performance of animals. Following the behavioral tests, all of the rats were sacrificed for evaluation of molecular alterations. Rats in the STZ-TQ group showed higher performance in passive avoidance test than rats in the STZ group whose memory performance declined compared to control group. The worse memory performance in STZ group was correlated with low number of surviving neurons and high number of degenerating neurons. In addition, an increase in APOE expression and a decrease in NGF expression were observed with STZ injection. Administration of TQ reversed these STZ-triggered cognitive and molecular alterations. In the present study, we observed the neuroregenerative effects of TQ by activation of JNK protein, upregulation of mir-124, and downregulation of ERK1/2 and NOS enzymes. The same ameliorative effect of TQ was also observed in the pTau protein expression. To sum up, we can say that the healing effect of TQ on STZ induced neurodegeneration opens a new door for the development of Alzheimer's disease treatment using natural products as an adjuvant when their action mechanism was explained in detail.

Thymoquinone reduces spinal cord injury by inhibiting inflammatory response, oxidative stress and apoptosis via PPAR-γ and PI3K/Akt pathways

The present study used a mild contusion injury in rat spinal cord to determine that thymoquinone reduces inflammatory response, oxidative stress and apoptosis in a spinal cord injury (SCI) rat model and to demonstrate its possible molecular mechanisms. The rats in the thymoquinone group received 30 mg/kg thymoquinone once daily by intragastric administration from 3 weeks after surgery. Hematoxylin and eosin staining, Basso, Beattie and Bresnahan (BBB) scale and tissue water content detection were used in the present study to analyze the effect of thymoquinone on SCI. The activity of inflammatory response mediators, oxidative stress factors and caspase-3/9 was measured using ELISA kits. Furthermore, western blotting was performed to analyzed the protein expression levels of prostaglandin E2, suppressed cyclooxygenase-2 (COX-2) and activated peroxisome proliferator-activated receptor γ (PPAR-γ), PI3K and Akt. The results from the study demonstrated that thymoquinone increased Basso, Beattie and Bresnahan score and decreased water content in spinal cord tissue. Treatment with thymoquinone decreased inflammatory response [measured by levels of tumor necrosis factor α, interleukin (IL)-1β, IL-6 and IL-18], oxidative stress (measured by levels of superoxide dismutase, catalase, glutathione and malondialdehyde) and cell apoptosis (measured by levels of caspase-3 and caspase-9) in SCI rats. Thymoquinone treatment inhibited prostaglandin E2 activity, suppressed COX-2 protein expression and activated PPAR-γ, PI3K and p-Akt protein expression in SCI rats. These data revealed that thymoquinone reduces inflammatory response, oxidative stress and apoptosis via PPAR-γ and PI3K/Akt pathways in an SCI rat model.

Thymoquinone Can Improve Neuronal Survival and Promote Neurogenesis in Rat Hippocampal Neurons

SCOPE

Thymoquinone (TQ) has been used as a potential therapeutic for diseases such as cancer and diabetes. Herein, we aim to investigate the effect of TQ on behavioral and molecular parameters in healthy rat hippocampus.

METHODS

TQ (20 mg kg^-1  d^-1 ) is administered intragastrically for 15 days to adult rats. After behavioral tests, the hippocampal tissues are investigated at the histological and molecular levels.

RESULTS

In both dentate gyrus and cornu ammonis 1, TQ significantly increases the number of hippocampal neurons. This increase is supported by a significant increase in the doublecortin expression on both gene and protein levels. In addition, TQ significantly decreases the amount of Caspase-3 expression and the cleavage of poly ADP ribose polymerase, indicating a decrease in apoptosis. Further, ERK, GSK-3, JNK, CREB, and iNOS proteins are found to be positively regulated by TQ. However, the gene expression of synapsin, synaptophysin, NGF, AKT, Bax, NFkB, and p53 and the protein expression of BDNF and nNOS are not affected by TQ.

CONCLUSION

These findings suggest that TQ has an enhancing effect on cell survival and neurogenesis in healthy hippocampus, rather inducing apoptosis in damaged neurons. This may proceed via ERK/JNK and CREB signaling pathways as a candidate acting mechanism for TQ.

Molecular mechanisms of cardiac pathology in diabetes - Experimental insights

Diabetic cardiomyopathy is a distinct pathology independent of co-morbidities such as coronary artery disease and hypertension. Diminished glucose uptake due to impaired insulin signaling and decreased expression of glucose transporters is associated with a shift towards increased reliance on fatty acid oxidation and reduced cardiac efficiency in diabetic hearts. The cardiac metabolic profile in diabetes is influenced by disturbances in circulating glucose, insulin and fatty acids, and alterations in cardiomyocyte signaling. In this review, we focus on recent preclinical advances in understanding the molecular mechanisms of diabetic cardiomyopathy. Genetic manipulation of cardiomyocyte insulin signaling intermediates has demonstrated that partial cardiac functional rescue can be achieved by upregulation of the insulin signaling pathway in diabetic hearts. Inconsistent findings have been reported relating to the role of cardiac AMPK and β-adrenergic signaling in diabetes, and systemic administration of agents targeting these pathways appear to elicit some cardiac benefit, but whether these effects are related to direct cardiac actions is uncertain. Overload of cardiomyocyte fuel storage is evident in the diabetic heart, with accumulation of glycogen and lipid droplets. Cardiac metabolic dysregulation in diabetes has been linked with oxidative stress and autophagy disturbance, which may lead to cell death induction, fibrotic 'backfill' and cardiac dysfunction. This review examines the weight of evidence relating to the molecular mechanisms of diabetic cardiomyopathy, with a particular focus on metabolic and signaling pathways. Areas of uncertainty in the field are highlighted and important knowledge gaps for further investigation are identified. This article is part of a Special issue entitled Cardiac adaptations to obesity, diabetes and insulin resistance, edited by Professors Jan F.C. Glatz, Jason R.B. Dyck and Christine Des Rosiers.

Therapeutic Potential and Pharmaceutical Development of Thymoquinone: A Multitargeted Molecule of Natural Origin

Thymoquinone, a monoterpene molecule is chemically known as 2-methyl-5-isopropyl-1, 4-benzoquinone. It is abundantly present in seeds of Nigella sativa L. that is popularly known as black cumin or black seed and belongs to the family Ranunculaceae. A large number of studies have revealed that thymoquinone is the major active constituent in N. sativa oil this constituent is responsible for the majority of the pharmacological properties. The beneficial organoprotective activities of thymoquinone in experimental animal models of different human diseases are attributed to the potent anti-oxidant and anti-inflammatory properties. Thymoquinone has also been shown to alter numerous molecular and signaling pathways in many inflammatory and degenerative diseases including cancer. Thymoquinone has been reported to possess potent lipophilicity and limited bioavailability and exhibits light and heat sensitivity. Altogether, these physiochemical properties encumber the successful formulation for the delivery of drug in oral dosages form and restrict the pharmaceutical development. In recent past, many efforts were undertaken to improve the bioavailability for clinical usage by manipulating the physiochemical parameters. The present review aimed to provide insights regarding the physicochemical characteristics, pharmacokinetics and the methods to promote pharmaceutical development and endorse the clinical usage of TQ in future by overcoming the associated physiochemical obstacles. It also enumerates briefly the pharmacological and molecular targets of thymoquinone as well as the pharmacological properties in various diseases and the underlying molecular mechanism. Though, a convincing number of experimental studies are available but human studies are not available with thymoquinone despite of the long history of use of black cumin in different diseases. Thus, the clinical studies including pharmacokinetic studies and regulatory toxicity studies are required to encourage the clinical development of thymoquinone.

High Glucose Induces Mouse Mesangial Cell Overproliferation via Inhibition of Hydrogen Sulfide Synthesis in a TLR-4-Dependent Manner

Background/Aims: Overproliferation of mesangial cells was believed to play an important role in the progress of diabetic nephropathy, one of the primary complications of diabetes. Hydrogen sulfide (H2S), a well-known and pungent gas with the distinctive smell of rotten eggs, was discovered to play a protective role in diabetic nephropathy. Methods: MTT assay was used to examine the viability of mesangial cells. Small interfering RNA was used to knock down the expression of TLR4 while specific inhibitor LY294002 to suppress the function of PI3K. H2S generation rate was determined by a H2S micro-respiration sensor. Results: Glucose of 25mM induced significant mesangial cells proliferation, which was accomplished by significantly inhibited endogenous H2S synthesis. And exogenous H2S treatment by NaHS markedly mitigated the overproliferation of mouse mesangial cells. Furthermore, it was found that H2S deficiency could result in TLR4 activation. And H2S supplementation remarkably inhibited TLR4 expression and curbed the mesangial cell overproliferation. Besides, PI3K/Akt pathway inhibition also significantly ameliorated the cell overproliferation. Conclusion: High glucose (HG) induces mouse mesangial cell overproliferation via inhibition of hydrogen sulfide synthesis in a TLR-4-dependent manner. And PI3K/Akt pathway might also play a vital part in the HG-induced mesangial cell overproliferation.

Aspalathin Protects the Heart against Hyperglycemia-Induced Oxidative Damage by Up-Regulating Nrf2 Expression

Aspalathin (ASP) can protect H9c2 cardiomyocytes against high glucose (HG)-induced shifts in myocardial substrate preference, oxidative stress, and apoptosis. The protective mechanism of ASP remains unknown. However, as one of possible, it is well known that phytochemical flavonoids reduce oxidative stress via nuclear factor (erythroid-derived 2)-like 2 (Nrf2) activation resulting in up-regulation of antioxidant genes and enzymes. Therefore, we hypothesized that ASP protects the myocardium against HG- and hyperglycemia-induced oxidative damage by up-regulating Nrf2 expression in H9c2 cardiomyocytes and diabetic (db/db) mice, respectively. Using an oxidative stress RT² Profiler PCR array, ASP at a dose of 1 µM was demonstrated to protect H9c2 cardiomyocytes against HG-induced oxidative stress, but silencing of Nrf2 abolished this protective response of ASP and exacerbated cardiomyocyte apoptosis. Db/db mice and their non-diabetic (db/+) littermate controls were subsequently treated daily for six weeks with either a low (13 mg/kg) or high (130 mg/kg) ASP dose. Compared to nondiabetic mice the db/db mice presented increased cardiac remodeling and enlarged left ventricular wall that occurred concomitant to enhanced oxidative stress. Daily treatment of mice with ASP at a dose of 130 mg/kg for six weeks was more effective at reversing complications than both a low dose ASP or metformin, eliciting enhanced expression of Nrf2 and its downstream antioxidant genes. These results indicate that ASP maintains cellular homeostasis and protects the myocardium against hyperglycemia-induced oxidative stress through activation of Nrf2 and its downstream target genes.