The protective role of raltegravir in experimental acute lung injury in vitro and in vivo

Abstract

Disruption of pulmonary endothelial permeability and associated barrier integrity increase the severity of acute respiratory distress syndrome (ARDS). This study investigated the potential ability of the human immunodeficiency virus-1 (HIV-1) integrase inhibitor raltegravir to protect against acute lung injury (ALI) and the underlying mechanisms. Accordingly, the impact of raltegravir treatment on an in vitro lipopolysaccharide (LPS)-stimulated human pulmonary microvascular endothelial cell (HPMEC) model of ALI and an in vivo LPS-induced two-hit ALI rat model was examined. In the rat model system, raltegravir treatment alleviated ALI-associated histopathological changes, reduced microvascular permeability, decreased Evans blue dye extravasation, suppressed the expression of inflammatory proteins including HMGB1, TLR4, p-NF-kB, NLRP3, and MPO, and promoted the upregulation of protective proteins including claudin 18.1, VE-cadherin, and aquaporin 5 as measured via western blotting. Immunohistochemical staining further confirmed the ability of raltegravir treatment to reverse LPS-induced pulmonary changes in NLRP3, claudin 18.1, and aquaporin 5 expression. Furthermore, in vitro analyses of HPMECs reaffirmed the ability of raltegravir to attenuate LPS-induced declines in VE-cadherin and claudin 18.1 expression while simultaneously inhibiting NLRP3 activation and reducing the expression of HMGB1, TLR4, and NF-kB, thus decreasing overall vascular permeability. Overall, our findings suggested that raltegravir may represent a viable approach to treating experimental ALI that functions by maintaining pulmonary microvascular integrity.

Human pulmonary microvascular endothelial cells respond to DAMPs from injured renal tubular cells

“…NOD‐like receptors (NLRs) and toll‐like receptors (TLRs) are present in pulmonary endothelial cells and are known to signal in response to DAMPs. 8 , 12 , 13 , 14 , 55 We, therefore, asked whether genes in the NLR or TLR signaling pathways were differentially expressed in pulmonary HMVECs that were stimulated with supernatant from injured RTECs. Using bulk RNA sequencing we found a total of 2785 differentially expressed genes between HMVECs treated with necrotic supernatant vs media alone (Figure 2a ).…”

“…Our data also add to our understanding of PRR expression in human pulmonary microvascular endothelial cells. There are very few reports that we are aware of which show definitive expression of NLRP3 and TLR2 in human pulmonary MVECs 14 , 65 , 66 , 67 and the only available data regarding NOD1 and NOD2 in pulmonary HMVECs is based on response to synthetic ligands rather than protein expression. 8 Our data show expression of TLR2, NOD1, and NLRP3 protein, which suggests future work may benefit from focus on these PRRs.…”

“…DAMPs promote a sterile inflammatory response in the lung by binding to pattern recognition receptors (PRRs) constitutively expressed in the pulmonary endothelium. 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 We recently showed that DAMPs generated from injured renal tubular epithelial cells (RTECs) cause upregulation of PRRs, increase production of inflammatory mediators, and activate pro‐inflammatory signaling pathways in healthy renal tubular epithelium. 16 DAMPs, which contribute to injurious inflammation after renal ischemia–reperfusion injury (IRI), are likely released into the circulation where they encounter PRRs constitutively expressed in pulmonary endothelium.…”