Ca2+ Signaling and Proliferation via Ca2+-Sensing Receptors in Human Hepatic Stellate LX-2 Cells.

Hepatic stellate cells (HSCs) play a significant role in the development of chronic liver diseases. Hepatic damage activates HSCs and results in hepatic fibrosis. The functions of activated HSCs require an increase in the cytosolic Ca2+ concentration ([Ca2+]cyt). However, the regulatory mechanisms underlying Ca2+ signaling in activated HSCs remain largely unknown. In the present study, functional analyses of Ca2+-sensing receptors (CaSRs) were performed using activated human HSCs, LX-2. Expression analyses revealed that CaSR proteins were expressed in α-smooth muscle actin-positive LX-2 cells. Extracellular Ca2+ restoration (from 0 to 2.2 mM) increased [Ca2+]cyt in these cells. The extracellular Ca2+-induced increase in [Ca2+]cyt was reduced by the CaSR antagonists, NPS2143 and Calhex 231. Furthermore, the growth of LX-2 cells was blocked by NPS2143 and Calhex 231 in concentration-dependent manners (IC50 = 6.0 and 9.5 µM, respectively). LX-2 cell proliferation was also attenuated by NPS2143 and Calhex 231. In conclusion, CaSRs are functionally expressed in activated HSCs and regulate Ca2+ signaling and cell proliferation. The present results provide insights into the molecular mechanisms underlying hepatic fibrosis and will contribute to the development of potential therapeutic targets.

Calhex231 Alleviates High Glucose-Induced Myocardial Fibrosis via Inhibiting Itch-Ubiquitin Proteasome Pathway in Vitro.

Diabetic cardiomyopathy (DCM) is a major complication of diabetes, and features myocardial fibrosis as its main pathological feature. Calcium sensing receptor (CaSR) is a G protein-coupled receptor, which involves in myocardial fibrosis by regulation of calcium homeostasis. Calhex231, the CaSR inhibitor, is not clear whether it regulates myocardial fibrosis in DCM. In the present study, type 1 diabetic (T1D) rats and primary neonatal rat cardiac fibroblasts were used to observe the role of Calhex231. In vivo experiments showed that in the T1D group, contractile dysfunction and the deposition of collagen I and III were obvious after 12 weeks. In vitro experiments, we found that high glucose (HG) could increase the expression of CaSR, α-smooth muscle actin (α-SMA), transforming growth factor-ß1 (TGF-ß1) collagen I/III, matrix metalloproteinase-2 (MMP-2), MMP9, along with cardiac fibroblast migration and proliferation. We further demonstrated that CaSR activation increased intracellular Ca2+ concentration and upregulated the expression of Itch (atrophin-1 interacting protein 4), which resulted in increasing the ubiquitination levels of Smad7 and upregulating the expression of p-Smad2, p-Smad3. However, treatment with Calhex231 clearly inhibited the above-mentioned changes. Collectively these results suggest that Calhex231 could inhibit Itch-ubiquitin proteasome and TGF-ß1/Smads pathways, and then depress the proliferation of cardiac fibroblasts, along with the reduction deposition of collagen, alleviate glucose-induced myocardial fibrosis. Our findings indicate an important new mechanism for myocardial fibrosis, and suggest Calhex231 would be a new therapeutic agent for the treatment of DCM.

Protective effect of calcium-sensing receptor inhibitor Calhex231 on traumatic hemorrhagic shock rats / 中华创伤杂志

Objective To observe the protective effects of calcium-sensing receptor (CaSR) inhibitor Calhex231 on traumatic hemorrhagic shock rats. Methods 144 SD rats were divided into six groups by random number table method: normal group, shock group, lactated Ringer's solution (LR) group, LR + Calhex231 0.1 mg/kg group, LR + Calhex231 1 mg/kg group, and LR + Calhex231 5 mg/kg group, with 16 rats in each group for survival observation and 8 rats for hemodynamics test. 64 SD rats were divided into four groups: normal group, shock group, lactated Ringer's solution (LR) group, LR + Calhex231 1 mg/kg group, with 8 rats in each group for detecting organ blood flow and superior mesenteric artery vascular reactivity and the other 8 rats for mesenteric artery vascular reactivity. After the establishment of traumatic hemorrhagic shock model, the shock group did not receive resuscitation, and the LR group was resuscitated with LR equal to two times of the blood loss volume. The three LR + Calhex231 groups with different dosages were firstly given LR of equal volume to that of blood loss, and then the Calhex231 was dissolved into LR (equal to the blood loss volume) to resuscitate. The wound was ligated and sutured immediately after resuscitation. The effect of Calhex231 on animal's 24-hour survival since the beginning of resuscitation was observed. The hemodynamics including the mean arterial blood pressure (MAP), left intraventricular systolic pressure (LVSP), maximal rising, and declining rate of left intraventricular pressure (±dp/dtmax) were observed before shock, at the end of shock, 1 hour after resuscitation, and 2 hours after resuscitation. The effects of Calhex231 on vital organ blood flow and vascular reactivity were observed 2 hours after resuscitation. Results All the shock rats died within 9 hours after the shock model was established. The survival outcomes of LR group rats were slightly improved compared with the shock group rats(P ＜0.05). The survival time and 24 hour survival rate of LR + Calhex231 1 mg/kg group and LR + Calhex231 5 mg/kg group rats were significantly increased compared with the shock group rats (P ＜0.05). The hemodynamic indexes of LR + Calhex231 groups were higher than those of the LR group. The best effect was observed in LR + Calhex231 1 mg/kg group rats (P ＜ 0.01). The MAP, LVSP and ± dp/dtmax were restored to normal level (64.9％, 82.4％, 89.8％, and 77.8％, respectively). Meanwhile, the blood flow in liver and kidney of LR + Calhex231 1 mg/kg group rats were increased from 57.2％ and 41％ to 108.7％ and 95.1％, respectively. The vascular reactivity including superior mesenteric artery and mesenteric artery of LR + Calhex231 1 mg/kg group rats were also increased (P ＜0.01). Conclusions In rats with hemorrhagic shock, the calcium sensitive receptor inhibitor Calhex231 can improve the vascular reactivity, the hemodynamics, and the blood flow of important organs. It plays a role in protecting the cardiovascular function and reducing the mortality after traumatic hemorrhagic shock.

The calcilytics Calhex-231 and NPS 2143 and the calcimimetic Calindol reduce vascular reactivity via inhibition of voltage-gated Ca2+ channels.

The present study investigates the effect of commonly used negative and positive allosteric modulators of the calcium-sensing receptor (CaSR) on vascular reactivity. In wire myography studies, increasing [Ca2+]o from 1mM to 6mM induced concentration-dependent relaxations of methoxamine-induced pre-contracted rabbit mesenteric arteries, with 6mM [Ca2+]o producing almost complete relaxation. [Ca2+]o-induced relaxations were attenuated in the presence of the calcilytics Calhex-231 and NPS 2143, and abolished by the removal of the endothelium. In addition to their calcilytic effects, Calhex-231 and NPS 2143 also produced concentration-dependent inhibitions of methoxamine- or KCl-induced precontracted tone, which were unaffected by removal of the endothelium and unopposed in the presence of the calcimimetic Calindol. In vessels with depleted Ca2+ stores, contractions mediated by Ca2+ influx via voltage-gated Ca2+ channels (VGCCs) were inhibited by Calhex231. In freshly isolated single rabbit mesenteric artery smooth muscle cells, Calhex-231 and NPS 2143 inhibited whole-cell VGCC currents. Application of Calindol also inhibited methoxamine- and KCl-induced pre-contracted tone, and inhibited whole-cell VGCC currents. In conclusion, in addition to their CaSR-mediated actions in the vasculature, Calhex-231, NPS 2143 and Calindol reduce vascular contractility via direct inhibition of VGCCs.

The effects of extracellular calcium-sensing receptor ligands on the contractility of pregnant human myometrium in vitro.

Ligands for extracellular calcium-sensing (CaS) receptors inhibit oxytocin-induced contractions of the rat's uterus. In this study, we investigated whether the CaS receptor ligands calindol, cinacalcet, and calhex 231 have similar effects on pregnant human myometrium. We compared their effects to those of the calcium-channel blocker nifedipine. In conventional concentration-effect experiments, both the mean contractile force (MCF) and the maximum amplitude of contractions induced by 1 nmol/L oxytocin were inhibited by nifedipine. Calindol and cinacalcet were ineffective as inhibitors, while calhex-231 produced partial inhibition. When single 10 µmol/L doses were applied calhex-231 produced a slowly developing inhibition, reducing the MCF to 38%, and amplitude to 34%, of vehicle controls after 1 hour. In similar experiments, calindol was ineffective while cinacalcet weakly inhibited only the amplitude. Immunohistochemistry revealed sparse expression of CaS receptors in pregnant human myometrium.