miR-146a impedes the anti-aging effect of AMPK via NAMPT suppression and NAD^(+)/SIRT inactivation

Nicotinamide adenine dinucleotide(NAD^(+))is indispensable for the anti-aging activity of the sirtuin(SIRT)family enzymes.AMPactivated protein kinase(AMPK)upregulates NAD^(+)synthesis and SIRT activity in a nicotinamide phosphoribosyltransferase(NAMPT)-dependent manner.However,the molecular mechanisms that affect AMPK-driven NAMPT expression and NAD^(+)/SIRT activation remain unclear.In this study,we tried to identify senescence-associated microRNAs(miRNAs)that negatively regulate the cascade linking AMPK and NAMPT expression.miRNA-screening experiments showed that the expression of miR-146a increased in senescent cells but decreased following AMPK activation.Additionally,miR-146a overexpression weakened the metforminmediated upregulation of NAMPT expression,NAD^(+)synthesis,SIRT activity,and senescence protection,whereas treatment with the miR-146a inhibitor reversed this effect.Importantly,these findings were observed both in vitro and in vivo.Mechanistically,miR146a directly targeted the 3′-UTR of Nampt mRNA to reduce the expression of NAMPT.AMPK activators metformin and 5-aminoimidazole-4-carboxamide(AICAR)hindered miR-146a expression at the transcriptional level by promoting IκB kinase(IKK)phosphorylation to attenuate nuclear factor-kappaB(NF-κB)activity.These findings identified a novel cascade that negatively regulates the NAD^(+)/SIRT pathway by suppressing miR-146a-mediated NAMPT downregulation.Furthermore,our results showed that miR-146a impedes the anti-aging effect of AMPK.This mutual inhibitory relationship between miR-146a and AMPK enriches our understanding of the molecular connections between AMPK and SIRT and provides new insight into miRNA-mediated NAD^(+)/SIRT regulation and an intervention point for the prevention of aging and age-related diseases.

SeHed,a novel gene expression system with stress-evoked hydrogen peroxide elimination property and anti-aging effect

Dear Editor,The moderate level of reactive oxygen species(ROS)contributes to cellular functions such as proliferation,differentiation,and infection resistance,but the excessive level of ROS causes oxidative damage which underlies the basic mechanism for aging and geriatric diseases.1 Therefore,precisely managing cellular ROS levels,meaning to keep redox homeostasis properly,stands as an aim for health and longevity.Actually,this aim is challenging,as it asks not only to restrain excessive ROS accumulation at the right time and right place but also to guarantee proper ROS levels for fitting physiological requirements.Traditional ways for eliminating ROS put more attention on the efficiency and identified a variety of drugs and enzymes with antioxidant properties,known as enzymatic and non-enzymatic ROS scavengers,respectively.However,how to accurately manage the integrative effect of ROS scavengers in vivo remains a problem.Actually,the effectiveness of non-enzymatic antioxidants in vivo is controversial,explained mostly by the uncertainty to reach a given organ with the appropriate concentration or to work there persistently.2 As to enzymatic ROS scavengers,although their overexpression in a given place can be achieved,this mode is often unwieldy or harmful to intrinsic physiologic functions in cases.3 For this reason,we attempt to develop new ways for in vivo antioxidation,for establishing a high-quality balance between efficiency and safety.As the consequence,we innovated a gene expression system that can limit the excessive ROS accumulation but keep the physiological level of ROS.