Combination Treatment with Histone Deacetylase 3 and 6 Selective Inhibitors Attenuates Lipopolysaccharide‐Induced Acute Lung Injury (ALI) in Mice.

Abstract

Endothelial barrier dysfunction plays a pivotal role in ALI. We have previously shown that inhibitors of the 90KDa heat shock protein (Hsp90) reduce the magnitude of LPS‐induced ALI in mice. Inhibition of histone deacetylases (HDAC) 3 or 6 suppresses the Hsp90 chaperone function. We now show that selective inhibition of HDAC 3 or 6 has a protective role in LPS‐mediated ALI. In vitro experiments utilized human lung microvascular endothelial cells (HLMVEC). In vivo experiments were performed in C57BL/6 mice. Selective inhibitors of HDAC3 (5µM RGFP966) or HDAC6 (5µM Tubastatin A), alone or combined, decreased total HDAC activity in HLMVEC; furthermore, RGFP966 and Tubastatin attenuated LPS‐induced phosphorylation of the Hsp90 client protein, Akt. Additionally, either RGFP966 or Tubastatin A protected against the LPS‐induced decrease in HLMVEC permeability. In subsequent experiments, mice were injected intraperitoneally with either vehicle or a combination of RGFP966 and Tubastatin (at 10mg/kg, each). 24h later, vehicle or LPS were given intratracheally. 24h after LPS, bronchoalveolar lavage (BAL) was performed. LPS produced a profound inflammatory response, characterized by alveolar cellular infiltration, as reflected in an 8‐fold increase in BAL fluid cellular content. Additionally, LPS increased lung capillary permeability, as indicated by a 6‐fold increase in BAL fluid protein content. Pretreatment with the HDAC inhibitors significantly reduced both the inflammatory and hyper‐permeability response to LPS. These data suggest HDAC3 and HDAC6 as potential therapeutic targets in ALI/ARDS. (Supported by HL101902).