The HIV protease inhibitor Saquinavir attenuates sepsis-induced acute lung injury and promotes M2 macrophage polarization via targeting matrix metalloproteinase-9

Quan Li,Timothy R. Billiar,Yao Tong,Xiaoyin Niu,Xiaohu Yang,Xibing Ding,Bruce R. Pitt,Zhuang Yu,Zhixia Chen,Mengzhu Li,Renlingzi Zhang,Lingling Zhang

doi:10.1038/s41419-020-03320-0

Abstract

Imbalance of macrophage polarization plays an indispensable role in acute lung injury (ALI), which is considered as a promising target. Matrix metalloproteinase-9 (MMP-9) is expressed in the macrophage, and has a pivotal role in secreting inflammatory cytokines. We reported that saquinavir (SQV), a first-generation human immunodeficiency virus-protease inhibitor, restricted exaggerated inflammatory response. However, whether MMP-9 could regulate macrophage polarization and inhibit by SQV is still unknown. We focused on the important role of macrophage polarization in CLP (cecal ligation puncture)-mediated ALI and determined the ability of SQV to maintain M2 over M1 phenotype partially through the inhibition of MMP-9. We also performed a limited clinical study to determine if MMP-9 is a biomarker of sepsis. Lipopolysaccharide (LPS) increased MMP-9 expression and recombinant MMP-9 (rMMP-9) exacerbated LPS-mediated M1 switching. Small interfering RNA to MMP-9 inhibited LPS-mediated M1 phenotype and SQV inhibition of this switching was reversed with rMMP-9, suggesting an important role for MMP-9 in mediating LPS-induced M1 phenotype. MMP-9 messenger RNA levels in peripheral blood mononuclear cells of these 14 patients correlated with their clinical assessment. There was a significant dose-dependent decrease in mortality and ALI after CLP with SQV. SQV significantly inhibited LPS-mediated M1 phenotype and increased M2 phenotype in cultured RAW 264.7 and primary murine bone marrow-derived macrophages as well as lung macrophages from CLP-treated mice. This study supports an important role for MMP-9 in macrophage phenotypic switching and suggests that SQV-mediated inhibition of MMP-9 may be involved in suppressing ALI during systemic sepsis.

Highlights

Sepsis remains a leading cause of death in the intensive care unit[1], which has high rates of in-hospital mortality[2].Amplified inflammatory response in the early phase of sepsis has been reported as a major cause of acute lung injury (ALI) that is characterized by increased vascular permeability, intrapulmonary retention of neutrophils, and synthesis of proinflammatory cytokines[3]
Matrix metalloproteinase-9 (MMP-9) protein was in large part eliminated in the presence of siRNA to matrix metalloproteinases (MMPs)-9 (Fig. 1A). siRNA- to MMP-9-treated cells showed a significant decrease in LPS-mediated increases in M1 gene expression (interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), IL-1β, and inducible nitric oxide synthases (Fig. 1B) and significant increases in M2 gene expression (Arg[1], Mrc[1], Fizz[1], and IL-10; Fig. 1C)
We found that recombinant MMP-9 (rMMP-9), by itself, did not affect nuclear factor-κB (NF-κB) signaling, but in the presence of LPS, rMMP-9 significantly increased phospho-NF-κB proteins, including p-IKK, p-P65, and p-IκBα in RAW 264.7 cells (Fig. 1F). siRNA to MMP-9-treated cells showed a significant decrease in LPS-mediated increases in phosphoNF-κB proteins (Fig. 1G)

Summary

Introduction

Amplified inflammatory response in the early phase of sepsis has been reported as a major cause of acute lung injury (ALI) that is characterized by increased vascular permeability, intrapulmonary retention of neutrophils, and synthesis of proinflammatory cytokines[3]. Tong et al Cell Death and Disease (2021)12:67 and regulation of macrophage polarization may be a potential rational therapeutic target for mitigation of sepsis-induced ALI. Macrophages secrete various proinflammatory mediators, including interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and matrix metalloproteinases (MMPs) following lipopolysaccharide (LPS) stimulation[7]. The role of MMP-9 is somewhat unclear in ALI11 and may be specific to the cause of lung injury, the kinetics of underlying inflammation, concomitant changes in other MMP’s and/or the activity of endogenous inhibitors of MMP (e.g., tissue inhibitors of metalloproteinases (TIMPs))

Methods

Results

Conclusion