Targeting senescence induced by age or chemotherapy with a polyphenol-rich natural extract improves longevity and healthspan in mice.

Accumulating senescent cells within tissues contribute to the progression of aging and age-related diseases. Botanical extracts, rich in phytoconstituents, present a useful resource for discovering therapies that could target senescence and thus improve healthspan. Here, we show that daily oral administration of a standardized extract of Salvia haenkei (Haenkenium (HK)) extended lifespan and healthspan of naturally aged mice. HK treatment inhibited age-induced inflammation, fibrosis and senescence markers across several tissues, as well as increased muscle strength and fur thickness compared with age-matched controls. We also found that HK treatment reduced acutely induced senescence by the chemotherapeutic agent doxorubicin, using p16LUC reporter mice. We profiled the constituent components of HK by mass spectrometry, and identified luteolin-the most concentrated flavonoid in HK-as a senomorphic compound. Mechanistically, by performing surface plasmon resonance and in situ proximity ligation assay, we found that luteolin disrupted the p16-CDK6 interaction. This work demonstrates that administration of HK promotes longevity in mice, possibly by modulating cellular senescence and by disrupting the p16-CDK6 interaction.

The aryl hydrocarbon receptor suppresses cigarette-smoke-induced oxidative stress in association with dioxin response element (DRE)-independent regulation of sulfiredoxin 1.

The aryl hydrocarbon receptor (AhR) is a ubiquitously expressed receptor/transcription factor that mediates toxicological responses of environmental contaminants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Emerging evidence indicates that the AhR suppresses apoptosis and proliferation independent of exogenous ligands, including suppression of apoptosis by cigarette smoke, a key risk factor for chronic obstructive pulmonary disease (COPD). As cigarette smoke is a potent inducer of oxidative stress, a feature that may contribute to the development of COPD, we hypothesized that the AhR prevents smoke-induced apoptosis by regulating oxidative stress. Utilizing primary lung fibroblasts derived from AhR(+/+) and AhR(-/-) mice as well as A549 human lung adenocarcinoma cells deficient in AhR expression (A549-AhR(ko)), we first show that AhR(-/-) fibroblasts and A549-AhR(ko) epithelial cells have a significant increase in cigarette smoke extract (CSE)-induced oxidative stress compared to wild type. CSE induced a significant increase in the mRNA expression of key antioxidant genes, including Nqo1 and Srxn1, predominantly in AhR(+/+) fibroblasts, with significantly less induction in AhR(-/-) cells. The induction of Srxn1, but not Nqo1, was independent of dioxin-response element (DRE) binding as AhR(DBD/DBD) lung fibroblasts, which express an AhR incapable of binding the DRE, increased Srxn1 to a degree similar to wild-type cells in response to CSE. There was no difference in Nrf2 expression or activation based on AhR expression. Lung fibroblasts derived from COPD subjects have significantly less AhR protein expression compared with both never-smokers (Normal) and smokers (At Risk). Consequently, COPD-derived fibroblasts were less robust in their induction of both Nqo1 and Srxn1 mRNA after exposure to CSE, which also failed to activate the AhR in the COPD fibroblasts. Taken together, these results support a new role for the AhR in regulating antioxidant defense in lung structural cells, such that low AhR expression may facilitate the development or progression of COPD.

Aryl hydrocarbon receptor-dependent regulation of miR-196a expression controls lung fibroblast apoptosis but not proliferation.

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor implicated in the regulation of apoptosis and proliferation. Although activation of the AhR by xenobiotics such as dioxin inhibits the cell cycle and control apoptosis, paradoxically, AhR expression also promotes cell proliferation and survival independent of exogenous ligands. The microRNA (miRNA) miR-196a has also emerged as a regulator of proliferation and apoptosis but a relationship between the AhR and miR-196a is not known. Therefore, we hypothesized that AhR-dependent regulation of endogenous miR-196a expression would promote cell survival and proliferation. Utilizing lung fibroblasts from AhR deficient (AhR(-/-)) and wild-type (AhR(+/+)) mice, we show that there is ligand-independent regulation of miRNA, including low miR-196a in AhR(-/-) cells. Validation by qRT-PCR revealed a significant decrease in basal expression of miR-196a in AhR(-/-) compared to AhR(+/+) cells. Exposure to AhR agonists benzo[a]pyrene (B[a]P) and FICZ as well as AhR antagonist CH-223191 decreased miR-196a expression in AhR(+/+) fibroblasts concomitant with decreased AhR protein levels. There was increased proliferation only in AhR(+/+) lung fibroblasts in response to serum, corresponding to a decrease in p27(KIP1) protein, a cyclin-dependent kinase inhibitor. Increasing the cellular levels of miR-196a had no effect on proliferation or expression of p27(KIP1) in AhR(-/-) fibroblasts but attenuated cigarette smoke-induced apoptosis. This study provides the first evidence that AhR expression is essential for the physiological regulation of cellular miRNA levels- including miR-196a. Future experiments designed to elucidate the functional relationship between the AhR and miR-196a may delineate additional novel ligand-independent roles for the AhR.