DNA damage repair (DDR) is a safeguard for genome integrity maintenance. Increasing DDR efficiency could increase the yield of induced pluripotent stem cells (iPSC) upon reprogramming from somatic cells. The epigenetic mechanisms governing DDR during iPSC reprogramming are not completely understood. Our goal was to evaluate the splicing isoforms of histone variant macroH2A1, macroH2A1.1, and macroH2A1.2, as potential regulators of DDR during iPSC reprogramming. GFP-Trap one-step isolation of mtagGFP-macroH2A1.1 or mtagGFP-macroH2A1.2 fusion proteins from overexpressing human cell lines, followed by liquid chromatography-tandem mass spectrometry analysis, uncovered macroH2A1.1 exclusive interaction with Poly-ADP Ribose Polymerase 1 (PARP1) and X-ray cross-complementing protein 1 (XRCC1). MacroH2A1.1 overexpression in U2OS-GFP reporter cells enhanced specifically nonhomologous end joining (NHEJ) repair pathway, while macroH2A1.1 knock-out (KO) mice showed an impaired DDR capacity. The exclusive interaction of macroH2A1.1, but not macroH2A1.2, with PARP1/XRCC1, was confirmed in human umbilical vein endothelial cells (HUVEC) undergoing reprogramming into iPSC through episomal vectors. In HUVEC, macroH2A1.1 overexpression activated transcriptional programs that enhanced DDR and reprogramming. Consistently, macroH2A1.1 but not macroH2A1.2 overexpression improved iPSC reprogramming. We propose the macroH2A1 splicing isoform macroH2A1.1 as a promising epigenetic target to improve iPSC genome stability and therapeutic potential.

• Keywords
• DNA damage, cell reprogramming, induced pluripotent stem cells, macroH2A1.1,
• MeSH
• DNA MeSH
• Endothelial Cells metabolism   MeSH
• Histones * metabolism   MeSH
• Induced Pluripotent Stem Cells * metabolism   MeSH
• Humans MeSH
• Mice MeSH
• DNA Repair MeSH
• X-ray Repair Cross Complementing Protein 1 genetics   metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• DNA MeSH
• Histones * MeSH
• MACROH2A1 protein, human MeSH Browser
• X-ray Repair Cross Complementing Protein 1 MeSH
• XRCC1 protein, human MeSH Browser

Accumulation of senescent cells may drive age-associated alterations and pathologies. Senolytics are promising therapeutics that can preferentially eliminate senescent cells. Here, we performed a high-throughput automatized screening (HTS) of the commercial LOPAC®Pfizer library on aphidicolin-induced senescent human fibroblasts, to identify novel senolytics. We discovered the nociceptin receptor FQ opioid receptor (NOP) selective ligand 1-[1-(1-methylcyclooctyl)-4-piperidinyl]-2-[(3R)-3-piperidinyl]-1H-benzimidazole (MCOPPB, a compound previously studied as potential anxiolytic) as the best scoring hit. The ability of MCOPPB to eliminate senescent cells in in vitro models was further tested in mice and in C. elegans. MCOPPB reduced the senescence cell burden in peripheral tissues but not in the central nervous system. Mice and worms exposed to MCOPPB also exhibited locomotion and lipid storage changes. Mechanistically, MCOPPB treatment activated transcriptional networks involved in the immune responses to external stressors, implicating Toll-like receptors (TLRs). Our study uncovers MCOPPB as a NOP ligand that, apart from anxiolytic effects, also shows tissue-specific senolytic effects.

• Keywords
• Aging, NOP, Senescence, Senolytic,
• MeSH
• Anti-Anxiety Agents * pharmacology   MeSH
• Caenorhabditis elegans MeSH
• Senotherapeutics * MeSH
• Humans MeSH
• Ligands MeSH
• Mice MeSH
• Narcotic Antagonists pharmacology   MeSH
• Nociceptin MeSH
• Analgesics, Opioid MeSH
• Opioid Peptides MeSH
• Piperidines pharmacology   MeSH
• Receptors, Opioid MeSH
• High-Throughput Screening Assays MeSH
• Cellular Senescence * MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Anti-Anxiety Agents * MeSH
• Senotherapeutics * MeSH
• Ligands MeSH
• Narcotic Antagonists MeSH
• Analgesics, Opioid MeSH
• Opioid Peptides MeSH
• Piperidines MeSH
• Receptors, Opioid MeSH

Staining mice tissues for β-galactosidase activity is a fundamental tool to detect age- or disease-associated cellular senescence. However, reported analyses of positivity for senescence-associated β-galactosidase activity or for other markers of senescence in post-mitotic cells of healthy murine tissues have been fragmentary or inconclusive. Here, we attempted to independently deepen this knowledge using multiple senescence markers within the same cells of wild type mice entering middle age (9 months of age). A histochemistry protocol for the pH-dependent detection of β-galactosidase activity in several tissues was used. At pH 6, routinely utilized to detect senescence-associated β-galactosidase activity, only specific cellular populations in the mouse body (including Purkinje cells and choroid plexus in the central nervous system) were detected as strongly positive for β-galactosidase activity. These post-mitotic cells were also positive for other established markers of senescence (p16, p21 and DPP4), detected by immunofluorescence, confirming a potential senescent phenotype. These data might contribute to understanding the functional relation between the senescence-associated β-galactosidase activity and senescence markers in post-mitotic cells in absence of disease or advanced aging.

• Keywords
• markers, mice, senescence,
• MeSH
• beta-Galactosidase metabolism   MeSH
• Biomarkers metabolism   MeSH
• Immunohistochemistry MeSH
• Hydrogen-Ion Concentration MeSH
• Mitosis physiology   MeSH
• Mice, Inbred C57BL MeSH
• Mice MeSH
• Cellular Senescence physiology   MeSH
• Aging physiology   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• beta-Galactosidase MeSH
• Biomarkers MeSH