The RNA binding protein HuR regulates the senescence-associated secretory phenotype under conditions of oxidative stress

<b>Background:</b> COPD is associated with accelerated lung aging and cellular senescence, caused by increased levels of oxidative stress, mainly due to inhalation of cigarette smoke. HuR, a RNA-binding protein, has been shown to modulate the expression of sirtuin-1 and cellular senescence markers p16 and p21. However, the role of HuR in regulating the senescence-associated secretory phenotype (SASP) is unclear. <b>Aim:</b> To investigate the effects of HuR knockdown in the presence and absence of oxidative stress (H₂O₂) on senescence-associated secretory phenotype (SASP) in airway epithelial cells. <b>Methods:</b> Bronchial epithelial cells (BEAS2B) and primary small airway epithelial cells (SAEC, non-smokers) were transfected with siRNA against HuR +/- 100μM H₂O₂ mRNA levels were determined using qPCR. Matrix metalloprotease (MMP) activity in SAEC was assessed by zymography. <b>Results:</b> Gene silencing of HuR in BEAS2B increased mRNA expression of p16 (2-fold, p&lt;0.01), p21 (2-fold), IL-6 (10-fold, p&lt;0.01), CXCL-8 (4-fold, p&lt;0.01), MMP-2 (22-fold, p&lt;0.001) and reduced sirtuin-1 expression by 30% (n=6). HuR knockdown in the presence of H₂O₂ further elevated the expression of p16 (3-fold), IL-6 (39-fold, p&lt;0.01), CXCL-8 (10-fold, p&lt;0.05) and reduced sirtuin-1 expression by 46% (n=6). Gene silencing of HuR increased MMP-2 and MMP-9 activity in the presence and absence of oxidative stress, in SAECs (n=4). <b>Conclusion:</b> Gene silencing of HuR in the presence and absence of oxidative stress results in increased expression of inflammatory mediators, MMPs and senescence markers, suggesting HuR may play a role in regulation of the SASP in COPD.