Lack of miRNA-17 family mediates high glucose-induced PAR-1 upregulation in glomerular mesangial cells.

Upregulation of thrombin receptor protease-activated receptor 1 (PAR-1) is verified to contribute to chronic kidney diseases, including diabetic nephropathy; however, the mechanisms are still unclear. In this study, we investigated the effect of PAR-1 on high glucose-induced proliferation of human glomerular mesangial cells (HMCs), and explored the mechanism of PAR-1 upregulation from alteration of microRNAs. We found that high glucose stimulated proliferation of the mesangial cells whereas PAR-1 inhibition with vorapaxar attenuated the cell proliferation. Moreover, high glucose upregulated PAR-1 in mRNA level and protein expression while did not affect the enzymatic activity of thrombin in HMCs after 48 h culture. Then high glucose induced PAR-1 elevation was likely due to the alteration of the transcription or post-transcriptional processing. It was found that miR-17 family members including miR-17-5p, -20a-5p, and -93-5p were significantly decreased among the eight detected microRNAs only in high glucose-cultured HMCs, but miR-129-5p, miR-181a-5p, and miR-181b-5p were markedly downregulated in both high glucose-cultured HMCs and equivalent osmotic press control compared with normal glucose culture. So miR-20a was selected to confirm the role of miR-17 family on PAR-1 upregulation, finding that miR-20a-5p overexpression reversed the upregulation of PAR-1 in mRNA and protein levels induced by high glucose in HMCs. In summary, our finding indicated that PAR-1 upregulation mediated proliferation of glomerular mesangial cells induced by high glucose, and deficiency of miR-17 family resulted in PAR-1 upregulation.

High glucose upregulates PAR-1 in SH-SY5Y cells via deficiency of miR-20a and miR-190a.

Thrombin activity enhancement and its receptor protease-activated receptor 1 (PAR-1) activation play vital roles in neurologic deficits in the central nervous system. Our recent study showed that PAR-1 upregulation stimulated by chronic high glucose (HG) caused central neuron injury through neuroinflammation; however, the molecular mechanisms are far from clear. In the present study, we found that HG resulted in neuronal injury of SH-SY5Y cells as evidenced by decreased cell viability and increased lactate dehydrogenase release and elevated the mRNA level of PAR-1. Moreover, we predicted and determined several potential microRNAs (miRs) combining with the 3'-UTR of PAR-1 mRNA, finding that miR-20a-5p, miR-93-5p, and miR-190a-5p were significantly decreased in HG-cultured SH-SY5Y cells compared with control. Further, SH-SY5Y cells stably transfected with miR-20a-5p or miR-190a-5p mimic were established, and overexpression efficiency were confirmed. It was found that miR-20a-5p or miR-190a-5p overexpression markedly decreased PAR-1 mRNA level and protein expression in SH-SY5Y cells cultured with HG and normal glucose, indicating that miR-20a or miR-19a deficiency contributed to HG-induced PAR-1 upregulation. Together, our findings demonstrated that PAR-1 upregulation mediated HG-induced neuronal damage in central neurons, which was achieved through miR-20a or miR-190a deficiency.

Piperine, as a TAS2R14 agonist, stimulates the secretion of glucagon-like peptide-1 in the human enteroendocrine cell line Caco-2.

Piperine is reported to ameliorate common metabolic diseases, however, its molecular mechanism is still unclear. In the present study, we examined whether piperine could stimulate glucagon-like peptide-1 (GLP-1) secretion in a human enteroendocrine cell line, Caco-2, and explored the potential mechanisms from the activation of human bitter taste receptors (TAS2Rs). It was found that TAS2R14 was highly expressed in Caco-2 cells, far more than TAS2R4 and TAS2R10. Piperine and flufenamic acid (FA, a known TAS2R14 agonist) markedly increased intracellular calcium mobilization and significantly enhanced the GLP-1 secretion, accompanied by elevated levels of proglucagon mRNA in Caco-2 cells compared with the control. Moreover, piperine and FA activated TAS2R14 signaling as evidenced by the increased mRNA and protein levels of TAS2R14, and the protein expression of its downstream key molecules including phospholipase C ß2 (PLCß2) and a transient receptor potential channel melastatin 5 (TRPM5). On the other hand, a G protein ßγ subunit inhibitor Gallein or a PLC inhibitor U73122 alleviated piperine-stimulated GLP-1 secretion in Caco-2 cells. In the meantime, a flavanone hesperetin significantly attenuated piperine and FA induced the intracellular calcium mobilization and GLP-1 secretion. Furthermore, TAS2R14 knockdown reversed the piperine-triggered up-regulation of PLCß2 and TRPM5 as well as increased the GLP-1 secretion in Caco-2 cells by TAS2R14 shRNA transfection. In summary, our findings demonstrated that piperine promoted the GLP-1 secretion from enteroendocrine cells through the activation of TAS2R14 signaling. Moreover, TAS2R14 was likely a target of piperine in the alleviation of metabolic diseases.

Sarsasapogenin attenuates Alzheimer-like encephalopathy in diabetes.

BACKGROUND: A crosstalk exists between diabetes and Alzheimer's disease (AD), and diabetic encephalopathy displays AD-like disorders. Sarsasapogenin (Sar) has strong anti-inflammatory efficacy, showing neuroprotection and memory-enhancement effects. PURPOSE: This study aims to verify the ameliorative effects of Sar on diabetic encephalopathy in vivo and in vitro, and to clarify the mechanisms from attenuation of AD-like pathology. METHODS: Streptozotocin-induced type 1 diabetic rats and high glucose-cultured SH-SY5Y cells were used in this study. After Sar treatment (20 and 60 mg/kg) for consecutive 9 weeks, Morris water maze and novel object recognition tasks were performed. Hematoxylin-eosin staining was used for examining loss of neurons in CA1 area and ki67 expression for reflecting neurogenesis in DG area of hippocampus. Aß production pathway and tau phosphorylation kinase cascade were examined in these two models. RESULTS: Sar improved learning and memory ability, loss of neurons and reduction of neurogenesis in the hippocampus of diabetic rats. Moreover, Sar suppressed Aß overproduction due to up-regulation of BACE1 in protein and mRNA and tau hyperphosphorylation from inactivation of AKT/GSK-3ß cascade in the hippocampus and cerebral cortex of diabetic rats and high glucose-cultured SH-SY5Y cells, and PPARγ antagonism abolished the effects of Sar on key molecules in the two pathways. Additionally, it was found that high glucose-stimulated Aß overproduction was prior to tau hyperphosphorylation in neurons. CONCLUSION: Sar alleviated diabetic encephalopathy, which was obtained through inhibitions of Aß overproduction and tau hyperphosphorylation mediated by the activation of PPARγ signaling. Hence, Sar is a good candidate compound for AD-like disorders.

Hesperetin ameliorates diabetes-associated anxiety and depression-like behaviors in rats via activating Nrf2/ARE pathway.

Diabetes-associated affective disorders are of wide concern, and oxidative stress plays a vital role in the pathological process. This study was to investigate the cerebroprotective effects of hesperetin against anxious and depressive disorders caused by diabetes, exploring the potential mechanisms related to activation of Nrf2/ARE pathway. Streptozotocin-induced diabetic rats were intragastrically administrated with hesperetin (0, 50, and 150 mg/kg) for 10 weeks. Forced swimming test, open field test, and elevated plus maze were used to evaluate the anxiety and depression-like behaviors of rats. The brain was collected for assays of Nrf2/ARE pathway. Moreover, high glucose-cultured SH-SY5Y cells were used to further examine the neuroprotective effects of hesperetin and underlying mechanisms. Hesperetin showed anxiolytic and antidepressant effects in diabetic rats according to the behavior tests, and increased p-Nrf2 in cytoplasm and Nrf2 in nucleus followed by elevations in mRNA levels and protein expression of glyoxalase 1 (Glo-1) and γ-glutamylcysteine synthetase (γ-GCS) in brain, known target genes of Nrf2/ARE signaling. Moreover, hesperetin attenuated high glucose-induced neuronal damages through activation of the classical Nrf2/ARE pathway in SH-SY5Y cells. Further study indicated that PKC inhibition or GSK-3ß activation pretreatment attenuated even abolished the effect of hesperetin on the protein expression of Glo-1 and γ-GCS in high glucose-cultured SH-SY5Y cells. In summary, hesperetin ameliorated diabetes-associated anxiety and depression-like behaviors in rats, which was achieved through activation of the Nrf2/ARE pathway. Furthermore, an increase in nuclear Nrf2 phosphorylation from PKC activation and GSK-3ß inhibition contributed to the activation of Nrf2/ARE pathway by hesperetin.

Sarsasapogenin restores podocyte autophagy in diabetic nephropathy by targeting GSK3ß signaling pathway.

Podocyte injury following abnormal podocyte autophagy plays an indispensable role in diabetic nephropathy (DN), therefore, restoration of podocyte autophagy is considered as a feasible strategy for the treatment of DN. Here, we investigated the preventive effects of sarsasapogenin (Sar), the main active ingredient in Anemarrhena asphodeloides Bunge, on the podocyte injury in diabetic rats, and tried to illustrate the mechanisms underlying the effects in high glucose (HG, 40 mM)-treated podocytes (MPs). Diabetes model was established in rats with single streptozocin (60 mg· kg-1) intraperitoneal administration. The rats were then treated with Sar (20, 60 mg· kg-1· d-1, i.g.) or a positive control drug insulin (INS) (40 U· kg-1· d-1, i.h.) for 10 weeks. Our results showed that both Sar and insulin precluded the decreases of autophagy-related proteins (ATG5, Beclin1 and LC3B) and podocyte marker proteins (podocin, nephrin and synaptopodin) in the diabetic kidney. Furthermore, network pharmacology was utilized to assess GSK3ß as the potential target involved in the action of Sar on DN and were substantiated by significant changes of GSK3ß signaling in the diabetic kidney. The underlying protection mechanisms of Sar were explored in HG-treated MPs. Sar (20, 40 µM) or insulin (50 mU/L) significantly increased the expression of autophagy- related proteins and podocyte marker proteins in HG-treated MPs. Furthermore, Sar or insulin treatment efficiently regulatedphosphorylation at activation and inhibition sites of GSK3ß. To sum up, this study certifies that Sar meliorates experimental DN through targeting GSK3ß signaling pathway and restoring podocyte autophagy.

Sarsasapogenin ameliorates diabetes-associated memory impairment and neuroinflammation through down-regulation of PAR-1 receptor.

Sarsasapogenin (Sar), a natural steroidal compound, shows neuroprotection, cognition-enhancement, antiinflammation, antithrombosis effects, and so on. However, whether Sar has ameliorative effects on diabetes-associated cognitive impairment remains unknown. In this study, we found that Sar ameliorated diabetes-associated memory impairment in streptozotocin-induced diabetic rats, evidenced by increased numbers of crossing platform and percentage of time spent in the target quadrant in Morris water maze tests, and suppressed the nucleotide-binding domain and leucine-rich repeat containing protein 1 (NLRP1) inflammasome in hippocampus and cerebral cortex. Furthermore, Sar inhibited advanced glycation end-products and its receptor (AGEs/RAGE) axis and suppressed up-regulation of thrombin receptor protease-activated receptor 1 (PAR-1) in cerebral cortex. On the other hand, Sar mitigated high glucose-induced neuronal damages, NLRP1 inflammasome activation, and PAR-1 up-regulation in high glucose-cultured SH-SY5Y cells, but did not affect thrombin activity. Moreover, the effects of Sar were similar to those of a selective PAR-1 antagonist vorapaxar. Further studies indicated that activation of the NLRP1 inflammasome and NF-κB mediated the effect of PAR-1 up-regulation in high glucose condition by using PAR-1 knockdown assay. In summary, this study demonstrated that Sar prevented memory impairment caused by diabetes, which was achieved through suppressing neuroinflammation from activated NLRP1 inflammasome and NF-κB regulated by cerebral PAR-1. HIGHLIGHTS: Sarsasapogenin ameliorated memory impairment caused by diabetes in rats. Sarsasapogenin mitigated neuronal damages and neuroinflammation by down-regulating cerebral PAR-1. The NLRP1 inflammasome and NF-κB signaling mediated the pro-inflammatory effects of PAR-1. Sarsasapogenin was a pleiotropic neuroprotective agent and memory enhancer in diabetic rodents.

High-continuity genome assembly of the jellyfish Chrysaora quinquecirrha.

The Atlantic sea nettle ( Chrysaora quinquecirrha) has an important evolutionary position due to its high ecological value. However, due to limited sequencing technologies and complex jellyfish genomic sequences, the current C. quinquecirrha genome assembly is highly fragmented. Here, we used the most advanced high-throughput chromosome conformation capture (Hi-C) technology to obtain high-coverage sequencing data of the C. quinquecirrha genome. We then anchored these data to the previously published contig-level assembly to improve the genome. Finally, a high-continuity genome sequence of C. quinquecirrha was successfully assembled, which contained 1 882 scaffolds with a N50 length of 3.83 Mb. The N50 length of the genome assembly was 5.23 times longer than the previously released one, and additional analysis revealed that it had a high degree of genomic continuity and accuracy. Acquisition of the high-continuity genome sequence of C. quinquecirrha not only provides a basis for the study of jellyfish evolution through comparative genomics but also provides an important resource for studies on jellyfish growth and development.

Sarsasapogenin alleviates diabetic nephropathy through suppression of chronic inflammation by down-regulating PAR-1: In vivo and in vitro study.

BACKGROUND: Sarsasapogenin (Sar) shows good effects on diabetic nephropathy (DN) through inhibition of the NLRP3 inflammasome, yet the potential mechanism is not well known. PURPOSE: This study was designed to explore the regulation of thrombin and/or its receptor protease-activated receptor 1 (PAR-1) on the NLRP3 inflammasome and NF-κB signaling in DN condition, and further expounded the molecular mechanism of Sar on DN. METHODS: Streptozotocin-induced diabetic rats were treated by gavage with Sar (0, 20 and 60 mg/kg) for consecutive 10 weeks. Then urine and serum were collected for protein excretion, creatinine, urea nitrogen, and uric acid assay reflecting renal functions, renal tissue sections for periodic acid-Schiff staining and ki67 expression reflecting cell proliferation, and renal cortex for the NLRP3 inflammasome and NF-κB signaling as well as thrombin/PAR-1 signaling. High glucose-cultured human mesangial cells (HMCs) were used to further investigate the effects and mechanisms of Sar. RESULTS: Sar markedly ameliorated the renal functions and mesangial cell proliferation in diabetic rats, and suppressed activation of the NLRP3 inflammasome and NF-κB in renal cortex. Moreover, Sar remarkably down-regulated PAR-1 in protein and mRNA levels but didn't affect thrombin activity in kidney, although thrombin activity was significantly decreased in the renal cortex of diabetic rats. Meanwhile, high glucose induced activation of the NLRP3 inflammasome and NF-κB, and increased PAR-1 expression while didn't change thrombin activity in HMCs; however, Sar co-treatment ameliorated all the above indices. Further studies demonstrated that PAR-1 knockdown attenuated activation of the NLRP3 inflammasome and NF-κB, and Sar addition strengthened these effects in high glucose-cultured HMCs. CONCLUSION: Sar relieved DN in rat through inhibition of the NLRP3 inflammasome and NF-κB by down-regulating PAR-1 in kidney.

Thrombin/PAR-1 activation induces endothelial damages via NLRP1 inflammasome in gestational diabetes.

Gestational diabetes mellitus (GDM) is associated with an increased risk of progressing to type 2 DM and cardiovascular disease; however, the pathogenesis is still poorly understood. This study was to investigate roles of thrombin and its receptor protease-activated receptor 1 (PAR-1) and NLRP1 inflammasome in endothelial injury in GDM condition. Umbilical cord and plasma of GDM patients and high glucose (HG) cultured human umbilical vein endothelial cells (HUVECs) were used to examine the pathological changes of these pathways. Meanwhile, ameliorative effects and potential mechanisms of a natural product sarsasapogenin (Sar) were investigated in HUVECs. Thrombin/PAR-1 pathway, advanced glycation endproducts (AGEs) and their receptor (RAGE) axis, and the nucleotide-binding domain and leucine-rich repeat containing protein 1 (NLRP1) inflammasome were activated in GDM condition and HG-cultured HUVECs, accompanied by endothelial injury (decreased cell viability and increased lactate dehydrogenase release). Nevertheless, thrombin inhibition or PAR-1 antagonism caused decreases in AGEs formation and RAGE expression in HG-cultured HUVECs, while AGEs inhibition or RAGE antagonism declined PAR-1 expression not thrombin activity. Furthermore, thrombin inhibition or PAR-1 antagonism restrained NLRP1 inflammasome activation in HG-cultured HUVECs; meanwhile, NLRP1 expression and interleukin 18 levels were remarkably reduced in HG-cultured HUVECs after PAR-1 knockdown. Interestingly, Sar co-treatment could suppress thrombin/PAR-1 pathway, NLRP1 inflammasome, and AGEs/RAGE axis. Together, endothelial damages in GDM were likely due to enhanced interaction between AGEs/RAGE axis and thrombin/PAR-1 pathway, followed by NLRP1 inflammasome activation. Moreover, Sar may act as a protective agent against endothelial injury in chronic HG condition.

A novel compound AB-38b improves diabetes-associated cognitive decline in mice via activation of Nrf2/ARE pathway.

OBJECTIVE: Diabetes-associated cognitive decline (DACD) is increasingly being concerned, and oxidative stress plays a vital role in the pathological process. AB-38b is a novel synthetic compound with two specific active groups of biphenyl dicarboxylate and α, ß unsaturated ketone, showing good antioxidant activity. The aim of this study was to investigate the ameliorative effects of AB-38b on DACD in mice, and to explore the possible mechanisms from glyoxylase 1 (Glo-1) enhancement and NF-E2-related factor-2 (Nrf2) activation. METHODS: Experimental type 2 mouse model of diabetes with C57BL/6 mice was made through high-fat diet combining with intraperitoneal streptozotocin. Diabetic mice were treated by gavage with AB-38b (0, 10, 20 and 40 mg/kg) or resveratrol (40 mg/kg), a typical inducer of Nrf2, for 8 weeks. Cognitive performances were evaluated by the novel object recognition task. Then brain tissues were collected to assess hippocampal damages, protein glycation, Glo-1 functions and protein expression, and the classic Nrf2/ARE pathway. RESULT: AB-38b markedly increased the preference index to novel object and the number of neurons in hippocampal CA1 area of diabetic mice. AB-38b significantly elevated the activity and protein of Glo-1, while reduced the levels of advanced glycation end products (AGEs) and protein expression of its receptor RAGE. Moreover, AB-38b raised Nrf2 expression and phosphorylation, as well as the protein expression and enzymatic activity of γ-glutamylcysteine synthetase, a well-known gene of Nrf2/ARE pathway, in hippocampus of the diabetic mice. CONCLUSION: AB-38b improved the cognitive performances of diabetic mice, which was achieved via up-regulation of Glo-1 and activation of Nrf2/ARE pathway.

Hesperetin ameliorates diabetic nephropathy in rats by activating Nrf2/ARE/glyoxalase 1 pathway.

Diabetic nephropathy (DN) is one of the most common diabetic complications, and alpha-carbonyl aldehydes and their detoxicating enzyme glyoxalase 1 (Glo-1) play vital roles in pathogenesis of diabetic complications. The aim of this study was to evaluate the renoprotective effects of hesperetin against DN in rats, and to investigate mechanisms from the aspect of Nrf2/ARE/Glo-1 pathway. Streptozotocin-induced diabetic rats were treated orally with hesperetin (50 and 150 mg/kg), or nuclear factor erythroid-derived-2-like 2 (Nrf2) inducer tert-butylhydroquinone (tBHQ, 25 mg/kg) for 10 weeks. Then proteinuria, creatinine, urea nitrogen, and uric acid were assayed for renal functions, fibronectin and collagen IV levels by immunohistochemistry, as well as periodic acid-Schiff staining and electron microscope observation, were used to assess renal morphology. Glo-1 activity, protein, and mRNA levels and the classic Nrf2/ARE pathway were investigated. Moreover, advanced glycation endproducts (AGEs) and its receptor RAGE, interleukin-1ß and tumor necrosis factor-α levels were also examined in the kidney. Hesperetin markedly ameliorated the renal functions and structural changes of diabetic rats, accompanied by up-regulation of Glo-1 as well as inhibition of AGEs/RAGE axis and inflammation. Meanwhile, hesperetin caused significant increases in Nrf2 and p-Nrf2 levels, as well as up-regulation of γ-glutamylcysteine synthetase, a well-known target gene of Nrf2/ARE signaling. Our results demonstrated that hesperetin could slow down the pathological process of DN, and Glo-1 enhancement contributed to the beneficial effects, which was obtained by the activation of Nrf2/ARE pathway.

Neuroprotection of quercetin on central neurons against chronic high glucose through enhancement of Nrf2/ARE/glyoxalase-1 pathway mediated by phosphorylation regulation.

Although dietary flavonoid quercetin alleviates diabetes-associated cognitive decline in rodents, the mechanisms are not clearly clarified. This study was designed to investigate whether quercetin showed neuroprotection on central neurons against chronic high glucose through the enhancement of Nrf2/ARE/glyoxalase 1 (Glo-1) pathway. SH-SY5Y cells were divided into 8 groups: normal glucose, high glucose (HG), osmotic pressure control, solvent control, HG plus low, middle, high concentrations of quercetin, or Nrf2 activator (sulforaphane). After treatment for 72 h, the associated parameters were measured. We found quercetin and sulforaphane increased cell viability, and enhanced Glo-1 functions (Glo-1 activity, the reduced glutathione and advanced glycation end-products levels) as well as Glo-1 protein and mRNA levels in SH-SY5Y cells cultured with HG. Meanwhile, quercetin and sulforaphane activated Nrf2/ARE pathway, reflected by the raised Nrf2 and p-Nrf2 levels, and the elevated protein and mRNA levels of γ-glutamycysteine synthase (γ-GCS), a known target gene of Nrf2/ARE signaling. Moreover, Nrf2/ARE pathway was activated after pretreatment with a PKC activator, p38 MAPK inhibitor, or GSK-3ß inhibitor under the condition of HG, and quercetin addition further strengthened this pathway; however, PKC inhibition or GSK-3ß activation pretreatment reversed the effects of quercetin on the protein expression of γ-GCS in the HG condition. In summary, quercetin exerts the neuroprotection by enhancing Glo-1 functions in central neurons under chronic HG condition, which may be mediated by activation of Nrf2/ARE pathway; furthermore, the increased Nrf2 phosphorylation mediated by PKC activation and/or GSK-3ß inhibition may involve in the activation of Nrf2/ARE pathway.

Enhancement of glyoxalase 1, a polyfunctional defense enzyme, by quercetin in the brain in streptozotocin-induced diabetic rats.

Glyoxalase 1 (Glo-1) is an ubiquitous cellular enzyme that participates in the detoxification of methylglyoxal (MG), a cytotoxic byproduct of glycolysis that induces protein modification (advanced glycation end products [AGEs]), oxidative stress, and inflammation. The concentration of MG is elevated under high-glucose conditions, such as diabetes. Therefore, Glo-1 and MG have been implicated in the pathogenesis of diabetic encephalopathy. We investigated the effect of quercetin on brain damage that was caused by diabetes in rats and the mechanisms associated with Glo-1. Streptozotocin-induced diabetic rats were treated orally with quercetin (30, 60, and 90 mg/kg) or distilled water for 14 weeks. The temporal cortex and hippocampus were harvested and analyzed for different indices assays. Quercetin, especially at a high dose, increased the levels of reduced glutathione and the activity of superoxide dismutase and decreased the levels of AGEs, the receptor for AGEs (RAGE), and malondialdehyde in the diabetic brain. Quercetin also significantly decreased the levels of inflammatory markers (cyclooxygenase-2, interleukin-1ß, and tumor necrosis factor α) in diabetic brains. Most importantly, Glo-1 activity and protein expression were increased in quercetin-treated diabetic rat brains compared with untreated diabetic brains. These results indicate that quercetin exerts beneficial effects by decreasing protein glycation, oxidative stress, and inflammation through the upregulation of Glo-1, which may ameliorate diabetic encephalopathy.

Protective effects of sarsasapogenin against early stage of diabetic nephropathy in rats.

Rhizome of Anemarrhena asphodeloides Bunge (AA, family Liliaceae) has been widely used in China for thousands of years to treat febrile diseases and diabetes. Steroidal saponins from AA show good antidiabetes effects and ameliorate diabetic complications. This study was designed to investigate the effects of sarsasapogenin (Sar), a major sapogenin from AA, on diabetic nephropathy (DN) in rats, and to explore the possible mechanisms. Diabetic rats were divided into 3 groups treated orally with Sar (0, 20, or 60 mg/kg) and carboxymethylcellulose sodium, whereas normal rats for Sar (0 or 60 mg/kg) and carboxymethylcellulose sodium. We found that chronic treatment with Sar for 9 weeks significantly ameliorated renal dysfunction of diabetic rats, as evidenced by decreases in albuminuria, kidney weight index, serum uric acid, and morphologic changes such as extracellular matrix expansion and accumulation (fibronectin and collagen IV levels, etc.). Meanwhile, Sar treatment resulted in decreases in interleukin-18, NLRP3, and activated caspase 1 levels as well as advanced glycation endproducts (AGEs) and their receptor (RAGE) levels in the renal cortex of diabetic rats. However, Sar has no effects on the above indices in the normal rats. Therefore, Sar can markedly ameliorate diabetic nephropathy in rats via inhibition of NLRP3 inflammasome activation and AGEs-RAGE interaction.

Sarsasapogenin suppresses Aß overproduction induced by high glucose in HT-22 cells.

The aim of this study is to investigate effects and potential mechanisms of sarsasapogenin (Sar), an active component purified from Rhizoma Anemarrhenae, on high glucose-induced amyloid-beta (Aß) peptide overproduction in HT-22 cells. HT-22 cells were divided into normal glucose; high glucose (HG); HG co-treated with low, middle, and high concentration of Sar (1, 5, 25 µmol/L); and peroxisome proliferator-activated receptor γ (PPARγ) agonist (10 µmol/L pioglitazone). After treatment for 24 h, protein expression of Aß and ß-site Aß precursor protein cleaving enzyme 1 (BACE1) and activated PPARγ level were determined by Western blot; Aß42 levels were also measured by using both immunofluorescence and ELISA methods. BACE1 activity and mRNA level were assessed by fluorospectrophotometry and quantitative PCR, respectively. Cell viability was assayed with a CCK-8 kit. Elevated Aß expression and Aß42 level were found in HG-treated HT-22 cells, accompanied by increased BACE1 protein and mRNA levels as well as enzymatic activity, which was markedly attenuated by three concentrations of Sar and pioglitazone. Moreover, HG reduced nuclear PPARγ levels, which was reversed by middle and high concentrations of Sar as well as pioglitazone. PPARγ antagonist GW9662 (20 µmol/L) pretreatment reversed the effect of Sar on BACE1 protein expression in HG-cultured HT-22 cells. Additionally, Sar suppressed HG-induced decreases in cell viability of HT-22 cells. High glucose can induce an increase in Aß levels and a decrease in cell viability in HT-22 cells, while co-treatment with Sar improves these results, which is mediated likely through activation of PPARγ and subsequent downregulation of BACE1.

Mangiferin Upregulates Glyoxalase 1 Through Activation of Nrf2/ARE Signaling in Central Neurons Cultured with High Glucose.

Mangiferin, a natural C-glucoside xanthone, has anti-inflammatory, anti-oxidative, neuroprotective actions. Our previous study showed that mangiferin could attenuate diabetes-associated cognitive impairment of rats by enhancing the function of glyoxalase 1 (Glo-1) in brain. The aim of this study was to investigate whether Glo-1 upregulation by mangiferin in central neurons exposed to chronic high glucose may be related to activation of Nrf2/ARE pathway. Compared with normal glucose (25 mmol/L) culture, Glo-1 protein, mRNA, and activity levels were markedly decreased in primary hippocampal and cerebral cortical neurons cultured with high glucose (50 mmol/L) for 72 h, accompanied by the declined Nrf2 nuclear translocation and protein expression of Nrf2 in cell nucleus, as well as protein expression and mRNA level of γ-glutamylcysteine synthetase (γ-GCS) and superoxide dismutase activity, target genes of Nrf2/ARE signaling. Nonetheless, high glucose cotreating with mangiferin or sulforaphane, a typical inducer of Nrf2 activation, attenuated the above changes in both central neurons. In addition, mangiferin and sulforaphane significantly prevented the formation of advanced glycation end-products (AGEs) reflecting Glo-1 activity, while elevated the level of glutathione, a cofactor of Glo-1 activity and production of γ-GCS, in high glucose cultured central neurons. These findings demonstrated that Glo-1 was greatly downregulated in central neurons exposed to chronic high glucose, which is expected to lead the formation of AGEs and oxidative stress damages. We also proved that mangiferin enhanced the function of Glo-1 under high glucose condition by inducing activation of Nrf2/ARE signaling pathway.

Neuroprotection of quercetin on central neurons against chronic high glucose through enhancement of Nrf2/Glo-1 mediated by phosphorylation regulation / 中国药理学与毒理学杂志

OBJECTIVE To investigate the neuroprotective effects of quercetin on central neurons against chronic high glucose in central neurons, in relation to Nrf2/ARE/Glo-1 activation. METHODS SH- SY5Y cells were cultured with high glucose (HG, 70 mmol · L- 1), 4- fold of the normal glucose (17.5 mmol · L- 1). Quercetin was set three concentrations (5, 10, 20 μmol · L- 1), with Nrf2 activator sulforaphane (SFN) as a positive group (2.5 μmol·L-1). After 72 h, cells were collected for glyoxalase 1 (Glo-1) activity and GSH level were by spectrophotometry; advanced glycation end-products (AGEs) as well as nuclear Nrf2 and p-Nrf2 levels by immunofluorescence; Glo-1, γ-glutamycysteine synthase (γ-GCS), Nrf2 and p-Nrf2 protein levels by Western blotting, and Glo-1 and γ-GCS mRNA levels by real-time qPCR. RESULTS Quercetin increased the cell viability of SH-SY5Y cells, and upregulated the levels of Glo-1 activity, protein, and mRNA in SH-SY5Y cells cultured with HG, accompanied by the elevated levels of glutathione, a cofactor of Glo-1 activity, and the reduced levels of AGEs. Meanwhile, quercetin could increase p- Nrf2 and Nrf2 levels in nucleus as well as p- Nrf2 levels in cytosol of SH-SY5Y cells exposed to chronic HG, accompanied by the elevated protein expression and mRNA levels of γ- GCS, a known target gene of Nrf2/ARE signaling. Moreover, a PKC activator or a p38 MAPK inhibitor pretreatment could significantly increase the protein expression of γ-GCS in HG condition, but an alkylating agent for sulfydryl of cysteine in Keap 1, a negative regulator of Nrf2, pretreatment only showed an increased tendency of γ-GCS protein, compared with without pretreatment; however, after pretreatment with those tool drugs, co-treatment with quercetin and HG had similar results to those of single tool drug pretreatment followed by HG exposure. CONCLUSION Firstly, quercetin can enhance Glo-1 function in central neurons, which is mediated by activation of Nrf2/ARE pathway, then exerts the neuroprotection against HG induced damage; moreover, PKC and p38 MAPK pathways may be involved in Nrf2 inactivation in chronic HG condition.

Ibuprofen attenuates nephropathy in streptozotocin­induced diabetic rats.

Ibuprofen, a commonly administered nonsteroidal anti­inflammatory therapeutic agent, is also a partial agonist of peroxisome proliferator­activated receptor Î³ (PPARγ). The present study investigated the effects of ibuprofen on type 1 diabetic nephropathy (DN) in rats, and the potential mechanisms associated with the activation of PPARγ. Diabetic rats were induced through a single intraperitoneal injection of streptozotocin before oral treatment with ibuprofen or pioglitazone for 8 weeks. The 24­h urine collection was performed for measurement of total protein content. The kidney was fixed in 10% formalin for periodic acid­Schiff and Masson's trichrome staining. Blood and residual kidney tissue samples were collected to measure the associated biochemical parameters. Chronic ibuprofen treatment decreased urinary protein excretion, blood urea nitrogen, glomerular basement membrane thickening and renal fibrosis, which were accompanied by increases in PPARγ protein expression, glutathione (GSH) level, and superoxide dismutase (SOD) activity, decreases in cyclooxygenase 2 and inducible nitric oxide synthase protein expressions, as well as a decreased interleukin 1ß (IL­1ß) level in the renal cortex of DN rats. Furthermore, the reduced IL­1ß level, increased GSH quantities and stronger SOD activity in the rat serum were evaluated in ibuprofen­treated diabetic rats and were compared with untreated diabetic rats. Regarding GSH and IL­1ß levels, ibuprofen was identified to be superior to the positive control, pioglitazone, while levels of the other indices were identified to be similar. Thus, ibuprofen was observed to prevent the development of DN, caused by type 1 diabetes, by anti­inflammatory and anti­oxidative action, potentially via PPARγ activation.