Carbon Monoxide Releasing Molecule-2-Upregulated ROS-Dependent Heme Oxygenase-1 Axis Suppresses Lipopolysaccharide-Induced Airway Inflammation.

Chih-Chung Lin,Chih-Chung Lin,Li-Der Hsiao,Li-Der Hsiao,Rou-Ling Cho,Chuen-Mao Yang

doi:10.3390/ijms20133157

Abstract

The up-regulation of heme oxygenase-1 (HO-1) is mediated through nicotinamaide adenine dinucleotide phosphate (NADPH) oxidases (Nox) and reactive oxygen species (ROS) generation, which could provide cytoprotection against inflammation. However, the molecular mechanisms of carbon monoxide-releasing molecule (CORM)-2-induced HO-1 expression in human tracheal smooth muscle cells (HTSMCs) remain unknown. Here, we found that pretreatment with CORM-2 attenuated the lipopolysaccharide (LPS)-induced intercellular adhesion molecule (ICAM-1) expression and leukocyte count through the up-regulation of HO-1 in mice, which was revealed by immunohistochemistrical staining, Western blot, real-time PCR, and cell count. The inhibitory effects of HO-1 by CORM-2 were reversed by transfection with HO-1 siRNA. Next, Western blot, real-time PCR, and promoter activity assay were performed to examine the HO-1 induction in HTSMCs. We found that CORM-2 induced HO-1 expression via the activation of protein kinase C (PKC)α and proline-rich tyrosine kinase (Pyk2), which was mediated through Nox-derived ROS generation using pharmacological inhibitors or small interfering ribonucleic acids (siRNAs). CORM-2-induced HO-1 expression was mediated through Nox-(1, 2, 4) or p47phox, which was confirmed by transfection with their own siRNAs. The Nox-derived ROS signals promoted the activities of extracellular signal-regulated kinase 1/2 (ERK1/2). Subsequently, c-Fos and c-Jun—activator protein-1 (AP-1) subunits—were up-regulated by activated ERK1/2, which turned on transcription of the HO-1 gene by regulating the HO-1 promoter. These results suggested that in HTSMCs, CORM-2 activates PKCα/Pyk2-dependent Nox/ROS/ERK1/2/AP-1, leading to HO-1 up-regulation, which suppresses the lipopolysaccharide (LPS)-induced airway inflammation.

Highlights

Heme oxygenase (HO), a rate-limiting enzyme, metabolizes heme to biliverdin-IXα, ferrous iron, and carbon monoxide (CO)
Our results demonstrated that carbon monoxide-releasing molecule (CORM)-2-induced heme oxygenase-1 (HO-1) expression is mediated via protein kinase C (PKC) α/proline-rich tyrosine kinase 2 (Pyk2)-dependent Nox/reactive oxygen species (ROS) generation linking to the extracellular signal-regulated kinase 1/2 (ERK1/2)-mediated activation of activator protein-1 (AP-1) in human tracheal smooth muscle cells (HTSMCs), which could protect against the lipopolysaccharide (LPS)-induced airway inflammatory diseases
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Summary

Introduction

Heme oxygenase (HO), a rate-limiting enzyme, metabolizes heme to biliverdin-IXα, ferrous iron, and carbon monoxide (CO). These secondary products are involved in the regulation of different physiological processes. The ferrous iron is rapidly sequestered with ferritin to function additional antioxidant and anti-apoptotic effects [5,6]. CO has been shown to exert anti-apoptotic and anti-inflammatory effects that are mediated via HO-1 up-regulation [4,7,8]. Accumulating evidence concerning HO-1/CO-dependent cytoprotection elicits the mechanisms involved in the modulation of the inflammatory responses, including the down-regulation of pro-inflammatory mediators, atherosclerosis, ischemia-reperfusion systems, and airway disorders [8,13,14]

Methods

Results

Conclusion