Protective Effect of Silent Mating Type Information Regulation 2 Homolog 1 on TGF-β1 Pathway via mTOR in Diabetic Nephropathy

Objective: To demonstrate whether the expression of silent mating type information regulation 2 homolog 1 (SIRT1) affects the level of TGF-β1 and Smad3 in HEK293 cells through regulating mTOR. Methods: First, recombinant plasmids DNA (rSIRT1) and siRNA targeting SIRT1 were constructed which were transfected into Human Embryonic Kidney 293 cell (HEK293) cells, respectively. Then, the generation of intracellular ROS in cells was examined by flow cytometry using the oxidation-sensitive probe. Last, the expressions of TGF-β1, smad3, P53, mTOR, p-mTOR, LC3-I and LC3-II in cells were detected to observe the effect of SIRT1 on TGF-β1 Pathway by western blot analysis. Results: We demonstrated that overexpressing of SIRT1 may decrease TGF-β1 and Smad3 expression in HEK293 cells through regulating mTOR. In addition, the result is the opposite when SIRT1 was silent in HEK293 cells. Conclusions: SIRT1 is closely related to TGF-β1/Smad3 pathway that correlates with the regulation of mTOR and ROS generation and causes diabetic nephropathy. The available evidence implies that SIRT1 has great potential as a clinical target for the prevention and treatment of renal fibrosis in the development of DN.

miR-211 promotes lens epithelial cells apoptosis by targeting silent mating-type information regulation 2 homolog 1 in age-related cataracts

AIM： To detect the expression of miR-211 in age-related cataract tissue, explore the effects of miR-211 on lens epithelial cell proliferation and apoptosis, and identify its target gene.METHODS： This study used real-time quantitative polymerase chain reaction（RT-q PCR） to measure the expression of miR-211 and its predicted target gene [silent matingtype information regulation 2 homolog 1（SIRT1）] in 46 anterior lens capsules collected from age-related cataract patients. Human lens epithelial cell line（SRA01/04） cells were transfected with either miR-211 mimics, mimic controls, miR-211 inhibitors or inhibitor controls, 72 h after transfection, miR NA and protein expression of SIRT1 were measured using RT-qP CR and Western blotting; then cells were exposed to 200 μmol/L H2O2 for 1h, whereupon cell viability was measured by MTS assay, caspase-3 assay was performed. Dual luciferase reporter assay was performed to verify the relationship between miR-211 of SIRT1.RESULTS： Compared to the control group, expression of miR-211 was significantly increased（P〈0.001）, the miR NA and protein expression of SIRT1 were significantly decreased（P〈0.001） in the anterior lens capsules of patients with age-related cataracts. Relative to the control group, SIRT1 miR NA and protein levels in the miR-211 mimic group were significantly reduced, cell proliferation activity significantly decreased, and caspase-3 activity was significantly increased（P〈0.001）. In the miR-211 inhibitor group, SIRT1 miRNA and protein expression were significantly increased, cell proliferation activity significantly increased, and caspase-3 activity was significantly decreased（P〈0.001）. A dual luciferase reporter assay confirmed that SIRT1 is a direct target of miR-211.CONCLUSION： miR-211 is highly expressed in the anterior lens capsules of patients with age-related cataracts. By negatively regulating the expression of SIRT1, miR-211 promotes lens epithelial cell apoptosis and inhibits lens epithelial cell proliferation.

SIRT1 inhibits apoptosis of human lens epithelial cells through suppressing endoplasmic reticulum stress in vitro and in vivo

AIM:To explore the effect of silent information regulator factor 2-related enzyme 1(SIRT1)on modulating apoptosis of human lens epithelial cells(HLECs)and alleviating lens opacification of rats through suppressing endoplasmic reticulum(ER)stress.METHODS:HLECs(SRA01/04)were treated with varying concentrations of tunicamycin(TM)for 24h,and the expression of SIRT1 and C/EBP homologous protein(CHOP)was assessed using real-time quantitative polymerase chain reaction(RT-PCR),Western blotting,and immunofluorescence.Cell morphology and proliferation was evaluated using an inverted microscope and cell counting kit-8(CCK-8)assay,respectively.In the SRA01/04 cell apoptosis model,which underwent siRNA transfection for SIRT1 knockdown and SRT1720 treatment for its activation,the expression levels of SIRT1,CHOP,glucose regulated protein 78(GRP78),and activating transcription factor 4(ATF4)were examined.The potential reversal of SIRT1 knockdown effects by 4-phenyl butyric acid(4-PBA;an ER stress inhibitor)was investigated.In vivo,age-related cataract(ARC)rat models were induced by sodium selenite injection,and the protective role of SIRT1,activated by SRT1720 intraperitoneal injections,was evaluated through morphology observation,hematoxylin and eosin(H&E)staining,Western blotting,and RT-PCR.RESULTS:SIRT1 expression was downregulated in TMinduced SRA01/04 cells.Besides,in SRA01/04 cells,both cell apoptosis and CHOP expression increased with the rising doses of TM.ER stress was stimulated by TM,as evidenced by the increased GRP78 and ATF4 in the SRA01/04 cell apoptosis model.Inhibition of SIRT1 by siRNA knockdown increased ER stress activation,whereas SRT1720 treatment had opposite results.4-PBA partly reverse the adverse effect of SIRT1 knockdown on apoptosis.In vivo,SRT1720 attenuated the lens opacification and weakened the ER stress activation in ARC rat models.CONCLUSION:SIRT1 plays a protective role against TM-induced apoptosis in HLECs and slows the progression of cataract in rats by inhibiting ER stress.These findings suggest a novel strategy for cataract treatment focused on targeting ER stress,highlighting the therapeutic potential of SIRT1 modulation in ARC development.

Cardiovascular and nonalcoholic fatty liver disease:Sharing common ground through SIRT1 pathways

As a non-communicable disease,cardiovascular disorders have become the lea-ding cause of death for men and women.Of additional concern is that cardio-vascular disease is linked to chronic comorbidity disorders that include nonal-coholic fatty liver disease(NAFLD).NAFLD,also termed metabolic-dysfunction-associated steatotic liver disease,is the greatest cause of liver disease throughout the world,increasing in prevalence concurrently with diabetes mellitus(DM),and can progress to nonalcoholic steatohepatitis that leads to cirrhosis and liver fi-brosis.Individuals with metabolic disorders,such as DM,are more than two times likely to experience cardiac disease,stroke,and liver disease that includes NAFLD when compared individuals without metabolic disorders.Interestingly,cardiovascular disorders and NAFLD share a common underlying cellular me-chanism for disease pathology,namely the silent mating type information regu-lation 2 homolog 1(SIRT1;Saccharomyces cerevisiae).SIRT1,a histone deacetylase,is linked to metabolic pathways through nicotinamide adenine dinucleotide and can offer cellular protection though multiple avenues,including trophic factors such as erythropoietin,stem cells,and AMP-activated protein kinase.Translating SIRT1 pathways into clinical care for cardiovascular and hepatic disease can offer significant hope for patients,but further insights into the complexity of SIRT1 pathways are necessary for effective treatment regimens.

Targeting the core of neurodegeneration:FoxO,mTOR,and SIRT1

The global increase in lifespan noted not only in developed nations,but also in large developing countries parallels an observed increase in a significant number of noncommunicable diseases,most notable neurodegenerative disorders.Neurodegenerative disorders present a number of challenges for treatment options that do not resolve disease progression.Furthermore,it is believed by the year 2030,the services required to treat cognitive disorders in the United States alone will exceed$2 trillion annually.Mammalian forkhead transcription factors,silent mating type information regulation 2 homolog 1(Saccharomyces cerevisiae),the mechanistic target of rapamycin,and the pathways of autophagy and apoptosis offer exciting avenues to address these challenges by focusing upon core cellular mechanisms that may significantly impact nervous system disease.These pathways are intimately linked such as through cell signaling pathways involving protein kinase B and can foster,sometimes in conjunction with trophic factors,enhanced neuronal survival,reduction in toxic intracellular accumulations,and mitochondrial stability.Feedback mechanisms among these pathways also exist that can oversee reparative processes in the nervous system.However,mammalian forkhead transcription factors,silent mating type information regulation 2 homolog 1,mechanistic target of rapamycin,and autophagy can lead to cellular demise under some scenarios that may be dependent upon the precise cellular environment,warranting future studies to effectively translate these core pathways into successful clinical treatment strategies for neurodegenerative disorders.

Novel nervous and multi-system regenerative therapeutic strategies for diabetes mellitus with mTOR

Throughout the globe,diabetes mellitus（DM） is increasing in incidence with limited therapies presently available to prevent or resolve the significant complications of this disorder.DM impacts multiple organs and affects all components of the central and peripheral nervous systems that can range from dementia to diabetic neuropathy.The mechanistic target of rapamycin（m TOR） is a promising agent for the development of novel regenerative strategies for the treatment of DM.m TOR and its related signaling pathways impact multiple metabolic parameters that include cellular metabolic homeostasis,insulin resistance,insulin secretion,stem cell proliferation and differentiation,pancreatic β-cell function,and programmed cell death with apoptosis and autophagy.m TOR is central element for the protein complexes m TOR Complex 1（m TORC1） and m TOR Complex 2（m TORC2） and is a critical component for a number of signaling pathways that involve phosphoinositide 3-kinase（PI 3-K）,protein kinase B（Akt）,AMP activated protein kinase（AMPK）,silent mating type information regulation 2 homolog 1（Saccharomyces cerevisiae）（SIRT1）,Wnt1 inducible signaling pathway protein 1（WISP1）,and growth factors.As a result,m TOR represents an exciting target to offer new clinical avenues for the treatment of DM and the complications of this disease.Future studies directed to elucidate the delicate balance m TOR holds over cellular metabolism and the impact of its broad signaling pathways should foster the translation of these targets into effective clinical regimens for DM.