TY - JOUR T1 - Base Excision Repair Proteins Are Required for Integrin-Mediated Suppression of Bleomycin-Induced DNA Breakage in Murine Lung Endothelial Cells JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 318 LP - 326 DO - 10.1124/jpet.106.113498 VL - 321 IS - 1 AU - Jane L. Rose AU - Kevin C. Reeves AU - Rostislav I. Likhotvorik AU - Dale G. Hoyt Y1 - 2007/04/01 UR - http://jpet.aspetjournals.org/content/321/1/318.abstract N2 - Engagement of integrin cell adhesion receptors suppresses bleomycin (BLM)-induced DNA strand breakage in endothelial cells. Previous investigation of cells from poly(ADP-ribose) polymerase (PARP)-1 knockout mice and with an inhibitor of the enzyme indicated that this facilitator of base excision repair (BER) is required for integrin-mediated suppression of DNA strand breakage. Here, small inhibitory RNA (siRNA) was used to assess the requirement for the BER proteins, DNA ligase III (Lig3) α, PARP-1, and X-ray repair complementing defective repair in Chinese hamster cells 1 (XRCC1), and for the long-patch BER ligase, DNA ligase I (Lig1), in integrin-mediated protection from BLM-induced DNA breakage. Murine lung endothelial cells (MLECs) were transfected with siRNA, treated with anti-β1 integrin antibody, and then BLM. 3′-OH in DNA and accumulation of phosphorylated histone H2AX (γH2AX), which reflects double-strand breakage, were measured. Integrin antibody inhibited the increases in 3′-OH caused by BLM in MLECs transfected with either control or Lig1 siRNA. However, after knockdown of Lig3α, PARP-1, or XRCC1, suppression of DNA breakage by integrin antibody was limited. BLM increased γH2AX levels, and integrin treatment inhibited this by 57 to 73% in MLECs transfected with control siRNA. Integrin engagement also inhibited increases in γH2AX in BLM-treated cells transfected with Lig1 siRNA. In contrast, Lig3α, PARP-1, and XRCC1 siRNAs prevented integrin-mediated inhibition of BLM-induced γH2AX levels. The results suggest that the BER proteins, Lig3α, PARP-1, and XRCC1, are required for integrin-mediated suppression of BLM-induced DNA breakage. The American Society for Pharmacology and Experimental Therapeutics ER -