Endoplasmic reticulum Ca2+ release causes Rieske iron-sulfur protein-mediated mitochondrial ROS generation in pulmonary artery smooth muscle cells.

Dapeng Dong,Ping Zhang,Tao Wang,Xiaodong Liang,Zhenghua Fei,Qiongyu Hao,Fei Han

doi:10.1042/bsr20192414

Abstract

Mitochondrial reactive oxygen species (ROS) cause Ca2+ release from the endoplasmic reticulum (ER) via ryanodine receptors (RyRs) in pulmonary artery smooth muscle cells (PASMCs), playing an essential role in hypoxic pulmonary vasoconstriction (HPV). Here we tested a novel hypothesis that hypoxia-induced RyR-mediated Ca2+ release may, in turn, promote mitochondrial ROS generation contributing to hypoxic cellular responses in PASMCs. Our data reveal that application of caffeine to elevate intracellular Ca2+ concentration ([Ca2+]i) by activating RyRs results in a significant increase in ROS production in cytosol and mitochondria of PASMCs. Norepinephrine to increase [Ca2+]i due to the opening of inositol 1,4,5-triphosphate receptors (IP3Rs) produces similar effects. Exogenous Ca2+ significantly increases mitochondrial-derived ROS generation as well. Ru360 also inhibits the hypoxic ROS production. The RyR antagonist tetracaine or RyR2 gene knockout (KO) suppresses hypoxia-induced responses as well. Inhibition of mitochondrial Ca2+ uptake with Ru360 eliminates N- and Ca2+-induced responses. RISP KD abolishes the hypoxia-induced ROS production in mitochondria of PASMCs. Rieske iron–sulfur protein (RISP) gene knockdown (KD) blocks caffeine- or NE-induced ROS production. Taken together, these findings have further demonstrated that ER Ca2+ release causes mitochondrial Ca2+ uptake and RISP-mediated ROS production; this novel local ER/mitochondrion communication-elicited, Ca2+-mediated, RISP-dependent ROS production may play a significant role in hypoxic cellular responses in PASMCs.

Highlights

Calcium ions (Ca2+) are one of the most crucial intracellular second messengers, involved in a plethora of cellular functions including cell survival and death, muscle contraction, regulation of metabolism, and gene expression [1]
Considering all the aforementioned descriptions, together with the fact that Ca2+ signaling is central to mitochondrial functions, possibly including reactive oxygen species (ROS) generation, in cardiac myocytes [25], we have proposed an exciting hypothesis that the hypoxia-induced, RyR2-mediated increase in [intracellular Ca2+ concentration (Ca2+]i) may promote mitochondrial ROS production, which provides a positive feedback revenue for the hypoxic ROS production, thereby contributing to attendant Ca2+ and contractile responses in pulmonary artery smooth muscle cell (PASMC)
Cells were treated with the classic Ryanodine Receptor (RyR) agonist caffeine (200 μM) for 5 min, ROS generation was remarkably increased in caffeine-treated cells compared with untreated cells by measuring DCFDA-derived fluorescence intensity (Figure 1A)

Summary

Introduction

Calcium ions (Ca2+) are one of the most crucial intracellular second messengers, involved in a plethora of cellular functions including cell survival and death, muscle contraction, regulation of metabolism, and gene expression [1]. Hypoxia causes strong vasoconstriction in pulmonary arteries, termed hypoxic pulmonary vasoconstriction (HPV) [1]. This unique response is an important adaptive mechanism for pulmonary ventilation/perfusion matching in the lungs, but may become a crucial pathological factor for pulmonary hypertension [2,3]. HPV results from an increase in intracellular Ca2+ concentration [Ca2+]i), which is mediated by multiple ion channels in PASMCs. A series of studies have revealed that ryanodine receptors (RyRs), the Ca2+ release channels on the Endoplasmic reticulum (ER), are important for the hypoxic increase in [Ca2+]i and contraction in PASMCs [4,5,6].

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Results

Conclusion