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Objective The aims of the study were to investigate the effects of human islet amyloid polypeptide (hIAPP) on autophagy in INS-1 cells and its underlying mechanism,and to explore the role of autophagy in hIAPP-induced cytotoxicity and oxidative stress.Methods INS-1 cells were treated with hIAPP (10 μmol/L) for 24 h in the presence or absence of N-acetyl-L-cysteine (NAC),compound C,5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) and 3-methyladenine (3-MA),respectively.Transmission electron microscopy was used to observe the number of autophagosome in cells.Cell viability was determined by methyl thiazolyl tetrazolium (MTT) test.2',7'-dichlorofluorescin diacetate (DCFH-DA) assay was used to measure the relative levels of reactive oxygen species (ROS).Western blot was used to detect expression of adenosine monophosphate-activated protein kinase (AMPK) and autophagic markers p62 and microtubule associated protein 1 light chain3 (LC3).Results Treatment of INS-1 cells with hIAPP resulted in a significant increase in the number of autophagosomes and the expression of LC3-Ⅱ/LC3-Ⅰ (both P＜0.05).Meanwhile,treatment of INS-1 cells with hIAPP enhanced the level of ROS to 1.76 times of control cells (P＜0.01).Co-treatment with NAC,an antioxidant,inhibited hIAPP-induced ROS generation,and the expression of LC3-Ⅱ/LC3-Ⅰ and p-AMPK in the INS-1 cells (all P＜0.05).Pretreatment of INS-1 cells with AMPK inhibitor compound C suppressed hIAPP and AICAR,an activator of AMPK,induced expression of LC3-Ⅱ/LC3-Ⅰ and p-AMPK (all P＜0.05).Autophagic inhibitor 3-MA and compound C aggravated the hIAPP-induced cell death and ROS generation in INS-1 cells (All P＜0.05).The cytotoxic effects of hIAPP were significantly attenuated by co-treatment with AICAR (P＜0.05).Conclusion Autophagy may act as an adaptive mechanism to alleviate hIAPP-induced oxidative damage and toxicity in INS-1 cells.
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Cyclic diguanosine monophosphate (c-di-GMP) is a ubiquitous nucleotide second messenger present in a wide variety of bacteria. It regulates many important bacterial physiological functions such as biofilm formation, motility, adhesion, virulence and extracellular polysaccharide synthesis. It binds with many different proteins or RNA receptors, one of which is called riboswitch that is usually located at the 5'-untranslational region (5'-UTR) in some mRNA. Riboswitch usually comprises a specific ligand-binding (sensor) domain (named aptamer domain, AD), as well as a variable domain, termed expression platform (EP), to regulate expression of downstream coding sequences. When a specific metabolite concentration exceeds its threshold level, it will bind to its cognate riboswitch receptor to induce a conformational change of 5'-UTR, leading to modulation of downstream gene expression. Two classes of c-di-GMP-binding riboswitches (c-di-GMP-Ⅰ and c-di-GMP-Ⅱ) have been discovered that bind with this second messenger with high affinity to regulate diverse downstream genes, underscoring the importance of this unique RNA receptor in this pathway. Class Ⅰ c-di-GMP riboswitches are present in a wide variety of bacteria, and are most common in the phyla Firmicutes and Proteobacteria, while class Ⅱ c-di-GMP riboswitches typically function as allosteric ribozymes, binding to c-di-GMP to induce folding changes at atypical splicing site junctions to modulate downstream gene expression. This review introduces the discovery, classification, function, and also the affected downstream genes of c-di-GMP riboswitches.
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Objective: To study the effect of ghrelin on L-type calcium channel current (ICa-L) of ventricular myocytes in experimental rats. Methods: The single ventricular myocyte in experimental rats were obtained by enzymolysis method, and the whole-cell patch-clamp technique was used to investigate the effect of ghrelin on ICa-L of ventricular myocytes at different doses of 10 nmol/L, 100 nmol/L and 1μmol/L respectively. Results: Ghrelin at 10 nmol/L, 100 nmol/L and 1μmol/L may inhibit ICa-L at (8.95 ± 2.13) %, (31.18 ± 4.78) % and (64.63 ± 8.57)% respectively,P<0.05, and the current-voltage curve was shifted upwards. The channel half inactivation curve decreased from (-1.34 ± 1.9) mV to (-8.04 ± 1.32 ) mV, (9.76 ± 1.17) mV and (-11.81 ± 0.73) mV respectively,P<0.05, and the recovery time after inactivation was prolonged as τ value from (63.23 ± 9.32) to (98.95 ± 10.74), (109.56 ± 13.42) and (127.39 ± 16.13) respectively,P<0.05. Conclusion: Ghrelin may accelerate ICa-L inactivation and prolong the recovery time after inactivation. Ghrelin inhibits ICa-L in a dose-dependent manner.
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Objective To explore the effects of wogonin on hyperlipidemia in mice and clarify the molecule mechanism. Methods Thirty mice were evenly divided into three group normal control group,model control group and treatment group. The normal control group was given normal diet,the model control group received high-fat diet,the treatment group received high-fat diet with wogonin (500 mg·kg-1 ). Results The mice developed hyperlipidemia 12 weeks after starting the high-fat diet. The body weight,visceral fat and fat index were increased (P<0. 05). After treatment,these indices were reduced ( P < 0. 01). Wogonin significantly reduced the total cholesterol ( TC),low density lipoprotein ( LDL),high density lipoprotein (HDL),except the triglyceride (TG). Compared to the model control group,the hepatic lipase(HL) and lipoprotein lipase(LPL) activity in the treatment group were recovered (P<0. 05),but HMG-CoA reductase activity was inhibited ( P<0. 01). Mechanistic study suggested that the lipid-lowering effect might be related to the lipid synthesis genes (SREBP-1c,FAS, PPARγ) and the lipid metabolism genes (PPARα,CPT-1). Conclusion Wogonin can prevent hyperlipidemia,which might be related to the regulation of enzyme activity and the changes of lipid synthesis and oxidative metabolism.