Genetic ablation of histone deacetylase 2 leads to lung cellular senescence and lymphoid follicle formation in COPD/emphysema

Histone deacetylase 2 (HDAC2), a critical determinant of chromatin remodeling, is reduced as a consequence of oxidative stress-mediated DNA damage and impaired repair. Cigarette smoke (CS) exposure causes DNA damage and cellular senescence. However, no information is available on the role of HDAC2 in CS-induced DNA damage, stress-induced premature senescence (SIPS), and senescence-associated secretory phenotype (SASP) during the pathogenesis of chronic obstructive pulmonary disease (COPD)/emphysema. We hypothesized that CS causes persistent DNA damage and cellular senescence via HDAC2-dependent mechanisms. We used HDAC2 global knockout (KO) and HDAC2 lung epithelial cell-specific KO [Clara cell-specific HDAC2 deletion (HDAC2 CreCC10)] mice to determine whether HDAC2 is a major player in CS-induced oxidative stress, SIPS, and SASP. HDAC2 KO mice exposed to CS show exaggerated DNA damage, inflammatory response, and decline in lung function leading to airspace enlargement. Chronic CS exposure augments lung senescence-associated β-galactosidase activity in HDAC2 KO, but not in HDAC2 CreCC10 mice. HDAC2 lung epithelial cell-specific KO did not further augment CS-induced inflammatory response and airspace enlargement but instead caused an increase in lymphoid aggregate formation. Our study reveals that HDAC2 is a key player regulating CS-induced DNA damage, inflammatory response, and cellular senescence leading to COPD/emphysema.-Sundar, I. K., Rashid, K., Gerloff, J., Rangel-Moreno, J., Li, D., Rahman, I. Genetic ablation of histone deacetylase 2 leads to lung cellular senescence and lymphoid follicle formation in COPD/emphysema.