Aging-rewired metabolic cues promote autophagy and senescence via DRAM1.

Being a major contributor to cell senescence and aging, DNA damage activates macroautophagy/autophagy, but how this process is affected by aging-rewired metabolism in normal biological systems remains to be explored. Here in cultured human umbilical cord-derived mesenchymal stem cells (HsMSCs) and the mouse liver that accumulate DNA damage during aging, we found an elevation of DRAM1 (DNA damage regulated autophagy modulator 1) and DRAM1-mediated pro-senescent autophagy (DMPA). Confirming that DRAM1 activated AMPK, we sought DMPA-associated metabolic features and noted substantial enrichment of N-acetylhistamine (N-AcHA) and phosphatidylethanolamine (PE) products in the aging HsMSCs and mouse liver. Elevating DNA damage and senescence, N-AcHA supplements were sufficient to upregulate DRAM1 and DMPA in primary hepatocytes from young mice but not even in pre-senescent HsMSCs, hence reflecting the differential tolerance of these cell models toward cytotoxic metabolic cues. The effects of N-AcHA were further verified in mouse aging and post-hepatectomy liver regeneration models. In contrast, accumulating cellular PE contents via ethanolamine supplements augmented autophagy but not DNA damage and senescence despite tending to induce DRAM1. Combined treatments with N-AcHA and ethanolamine were sufficient to trigger DMPA in HsMSCs. Despite their differential cellular responses toward N-AcHA and ethanolamine supplements, in primary HsMSCs and mouse hepatocytes DMPA did not notably downregulate SQSTM1/p62 proteins, which differed from general macroautophagy and may constitutively support the fusion of SQSTM1-modified cargo-containing autophagosomes with lysosomes. Overall, this study reveals DMPA-promoting metabolic and molecular features. Thus, targeting certain metabolic pathways and DMPA may promote DNA repair and delay senescence/aging.Abbreviations: ATM: ATM serine/threonine kinase; ATG5: autophagy related 5; ACTB: actin beta; BaFA1: bafilomycin A(1); CDKN1A/p21: cyclin dependent kinase inhibitor 1A; DDR: DNA damage response; DEGs: differentially expressed genes; DRAM1: DNA damage regulated autophagy modulator 1; DMPA: DRAM1-mediated pro-senescent autophagy; DPMPs: differentially presented metabolic products; ETO: etoposide; Eth: ethanolamine; GL: glycerolipids; GP: glycerophospholipids; γ-H2AX: phosphorylated H2A.X variant histone; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; HsMSC: human mesenchymal stem cell; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MSA: methanesulfonic acid; N-AcHA: N-acetylhistamine; PE: phosphatidylethanolamine; PHx: partial hepatectomy; PCYT2: phosphate cytidyltransferase 2, ethanolamine; SASP: senescence-associated secretory phenotype; SA-GLB1/β-gal: senescence-associated galactosidase beta 1; SQSTM1/p62: sequestosome 1; TAF: telomere-associated foci; TP53/p53: tumor protein p53.