CD38-mediated Ca2+ Signaling Contributes to Angiotensin II-induced Activation of Hepatic Stellate Cells: ATTENUATION OF HEPATIC FIBROSIS BY CD38 ABLATION

Seon-Young Kim,Baik Hwan Cho,Uh-Hyun Kim

doi:10.1074/jbc.m109.076216

Seon-Young Kim, Baik Hwan Cho + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m109.076216

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Abstract

CD38 is a type II glycoprotein that is responsible for the synthesis and hydrolysis of cyclic ADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP), Ca(2+)-mobilizing second messengers. The activation of hepatic stellate cells (HSCs) is a critical event in hepatic fibrosis because these cells are the main producers of extracellular matrix proteins in the liver. Recent evidence indicates that the renin-angiotensin system plays a major role in liver fibrosis. In this study, we showed that angiotensin II (Ang II) evoked long lasting Ca(2+) rises and induced NAADP or cADPR productions via CD38 in HSCs. Inositol 1,4,5-trisphosphate as well as NAADP-induced initial Ca(2+) transients were prerequisite for the production of cADPR, which was responsible for later sustained Ca(2+) rises in the Ang II-treated HSCs. Ang II-mediated inositol 1,4,5-trisphosphate- and NAADP-stimulated Ca(2+) signals cross-talked in a dependent manner with each other. We also demonstrated that CD38 plays an important role in Ang II-induced proliferation and overproduction of extracellular matrix proteins in HSCs, which were reduced by an antagonistic cADPR analog, 8-bromo-cADPR, or in CD38(-/-) HSCs. Moreover, we presented evidence to implicate CD38 in the bile duct ligation-induced liver fibrogenesis; infiltration of inflammatory cells and expressions of alpha-smooth muscle actin, transforming growth factor-beta1, collagen alphaI(1), and fibronectin were reduced in CD38(-/-) mice compared with those in CD38(+/+) mice. These results demonstrate that CD38-mediated Ca(2+) signals contribute to liver fibrosis via HSCs activation, suggesting that intervention of CD38 activation may help prevent hepatic fibrosis.

Highlights

Hepatic fibrosis represents a major medical problem worldwide with significant morbidity and mortality
We showed that angiotensin II (Ang II) evoked long lasting Ca2؉ rises and induced nicotinic acid adenine dinucleotide phosphate (NAADP) or cyclic adenosine diphosphoribose (cADPR) productions via CD38 in Hepatic stellate cells (HSCs)
We demonstrated that CD38 plays an important role in Ang II-induced proliferation and overproduction of extracellular matrix proteins in HSCs, which were reduced by an antagonistic cADPR analog, 8-bromo-cADPR, or in CD38؊/؊ HSCs

Summary

FIGURE NAADP

Ang II evoked sustained intracellular Ca2ϩ increase in CD38ϩ/ϩ. HSCs; the later phase of sustained Ca2ϩ signal was not detected in the Ang II-treated HSCs from CD38Ϫ/Ϫ mice Pretreatment of HSCs with 8-BrcADPR blocked the sustained Ca2ϩ increase, similar to that shown in (1:100; DakoCytomation). The stained sections were incu- CD38Ϫ/Ϫ HSCs (Fig. 2C), suggesting that Ang II-mediated long bated with biotinylated secondary antibody (DakoCytomation), lasting Ca2ϩ signaling in HSCs is due to the action of cADPR. The Ang II-mediated Ca2ϩ signal in HSCs consists of two phases of Ca2ϩ signals; initial Ca2ϩ transient is dependent on both IP3 and NAADP, whereas later sustained Ca2ϩ signal on cADPR (Fig. 2F). Statistical significance of difference between groups was duction in HSCs—To elucidate whether cADPR and NAADP determined using Student’s t test. Differences were considered are produced in Ang II-treated HSCs, we measured intracellusignificant if the p value was Ͻ0.05

RESULTS

DISCUSSION