Emodin increases Ca2+ influx through L-type Ca2+ channel in guinea pig gallbladder smooth muscle

Emodin repairs interstitial cells of Cajal damaged by cholelithiasis in the gallbladder

BACKGROUND

Hypercholesterolemia induces cholelithiasis and dysfunction of gallbladder motility. Interstitial cells of Cajal (ICCs) contribute to gallbladder motility. Emodin modulates the contractility of the gallbladder muscle; however, the underlying mechanism is unknown.

AIM

This study aimed to explore the effects of emodin on gallbladder ICCs with cholelithiasis in a guinea pig model.

METHODS

Animals were randomly divided into a healthy control group and three study groups. All study groups received a high-cholesterol diet (HCD) for 8 weeks. Subsequently, they were randomly assigned to either the HCD group or one of the emodin treatment groups lasting 4 or 8 weeks. Total cholesterol (TC) and triglycerides (TG) were measured to determine changes in serum lipid levels. Immunohistochemistry was performed to detect the morphology and number of ICCs. TUNEL assays were performed to detect ICC apoptosis. Transmission electron microscopy was employed to observe ICC structure. Western blotting and real-time polymerase chain reaction were used to detect changes in stem cell factor (SCF)/c-kit pathway expression.

RESULTS

Serum TC and TG were higher in all study groups. In cases of cholelithiasis, the SCF/c-kit pathway was downregulated, the number of gallbladder ICCs decreased, apoptosis increased, and the ICC network structure was damaged. After emodin treatment, the SCF/c-kit pathway was upregulated, the number of gallbladder ICCs increased, apoptosis decreased, and the ICC network structure recovered.

CONCLUSION

Cholelithiasis downregulates the SCF/c-kit pathway and damages gallbladder ICCs. Emodin upregulates the SCF/c-kit pathway and increases gallbladder ICCs, contributing to recovery from gallbladder motility disorders.\.

Synthetic imperatorin derivatives alleviate allergic reactions via mast cells

Anaphylaxis is a severe systemic allergic reaction that exhibits multiple clinical symptoms. The Mas-related G protein-coupled receptor X2 (MRGPRX2) is recognized as a key cell receptor mediating allergic diseases and drug-induced anaphylactoid reactions. Thus, it has been a promising target for preventing and treating these reactions. Based on the potential activity of imperatorin and active structural feature of MRGPRX2, we first demonstrated that the synthetic imperatorin derivatives (IDs) could significantly inhibit MRGPRX2 agonist-induced degranulation and cytokine release in LAD2 cells, as well as alleviate local and systemic anaphylaxis in mice. The IC₅₀ value of the most promising compound is an order of magnitude lower than that of imperatorin. IDs were further identified to display anti-pseudo-allergic activity by binding MRGPRX2 with the tertiary nitrogen substructures, just liking the reported MRGPRX2-ligand. These results would propose evidence for discovery of agents for treating MCs-dependent allergic disorders.

Emodin - A natural anthraquinone derivative with diverse pharmacological activities

Emodin (1,3,8-trihydroxy-6-methyl-anthraquinone) is a natural anthraquinone derivative that is present in numerous globally renowned herbal medicines. It is recognised as a protein tyrosine kinase inhibitor and as an anticancer drug, active against various tumour cells, including lung, breast, liver, and ovarian cancer cells. Recently, its role in combination chemotherapy with various allopathic medicines, to minimize their toxicity and to enhance their efficacy, has been studied. The use of emodin in these therapies is gaining popularity, due to fewer associated side effects compared with standard anticancer drugs. Emodin has a broad therapeutic window, and in addition to its antineoplastic activity, it displays anti-ulcer, anti-inflammatory, hepatoprotective, neuroprotective, antimicrobial, muscle relaxant, immunosuppressive and antifibrotic activities, in both in vitro and in vivo models. Although reviews on the anticancer activity of emodin have been published, none coherently unite all the pharmacological properties of emodin, particularly the anti-oxidant, antimicrobial, antidiabetic, immunosuppressive and hepatoprotective activities of the compound. Hence, in this review, all of the available data regarding the pharmacological properties of emodin are explored, with particular emphasis on the modes of action of the molecule. In addition, the manuscript details the occurrence, biosynthesis and chemical synthesis of the compound, as well as its toxic effects on biotic systems.

Effect of emodin on mobility signal transduction system of gallbladder smooth muscle in Guinea pig with cholelithiasis

OBJECTIVE

To study the effect of emodin on protein and gene expressions of the massagers in mobility signal transduction system of cholecyst smooth muscle cells in guinea pig with cholesterol calculus.

METHODS

The guinea pigs were randomly divided into 4 groups, such as control group, gall-stone (GS) group, emodin group and ursodeoxycholic acid (UA) group. Cholesterol calculus models were induced in guinea pigs of GS, emodin and UA groups by lithogenic diet, while emodin or UA were given to the corresponding group for 7 weeks. The histomorphological and ultrastructure change of gallbladder were detected by microscope and electron microscope, the content of plasma cholecystokinin (CCK) and [Ca²⁺]_i were analyzed successively by radioimmunoassay and flow cytometry. The protein and mRNA of Gsα, Giα and Cap in cholecyst cells were determined by western blotting and real time polymerase chain reaction (RT-PCR).

RESULTS

Emodin or UA can relieve pathogenic changes in epithelial cells and muscle cells in gallbladder of guinea pig with cholesterol calculus by microscope and transmission electron microscope. In the cholecyst cells of GS group, CCK levels in plasma and [Ca²⁺]_i decreased, the protein and mRNA of GS were down-regulated, the protein and mRNA of Gi and Cap were up-regulated. Emodin significantly decreased the formative rate of gallstone, improved the pathogenic change in epithelial cells and muscle cells, increased CCK levels in plasma and [Ca²⁺]_i in cholecyst cells, enhanced the protein and mRNA of Gs in cholecyst cells, reduced the protein and mRNA of Gi and Cap in cholecyst cells in guinea pig with cholesterol calculus.

CONCLUSION

The dysfunction of gallbladder contraction gives rise to the disorders of mobility signal transduction system in cholecyst smooth muscle cells, including low content of plasma CCK and [Ca²⁺]_i in cholecyst cells, abnormal protein and mRNA of Gs, Gi and Cap. Emodin can enhance the contractibility of gallbladder and alleviate cholestasis by regulating plasma CCK levels, [Ca²⁺]_i in cholecyst cells and the protein and mRNA of Gs, Gi and Cap.

Quercetin relaxes guinea pig gallbladder strips

Quercetin, a phytoestrogen and flavonoid, relaxes intestinal and vascular smooth muscle. The purpose of this study was to determine if quercetin had an effect on gallbladder smooth muscle. An in vitro technique was used to determine the effects of quercetin on gallbladder strips and which system(s) mediated the relaxation. Paired t tests were used; differences between means of P < .05 were considered significant. Adding quercetin before cholecystokinin or KCl produced a significant (P < .001) decrease in the amount of tension (0.80 ± 0.04 vs 0.48 ± 0.04 g cholecystokinin octapeptide and 0.8 ± 0.06 vs 0.54 ± 0.05 g KCl, respectively). When the protein kinase C (PKC) inhibitors bisindolymaleimide IV and chelerythrine Cl^- were simultaneously, a significant (P < .001) reduction in the quercetin-induced relaxation (45.7% ± 4.3% vs 27.6% ± 3.4%) was observed. To determine if protein kinase A (PKA) mediated the quercetin-induced relaxation, PKA inhibitor 14-22 amide myristolated was used. It significantly (P < .05) decreased the amount (40.4% ± 3.7% vs 34.5% ± 3.3%) of quercetin-induced relaxation. The use of 2-APB also significantly (P < .001) reduced the amount of quercetin-induced relaxation (51.2% ± 3.5% vs 14.8% ± 3.6%). l-N^G-methyl-l-arginine acetate salt, a nitric oxide synthase inhibitor, significantly (P < 001) decreased the quercetin-induced relaxation (45.7% ± 4.2% vs 35.2% ± 3.6%). KT5823, a PKC inhibitor, had no effect on the quercetin-induced relaxation. Quercetin blocked extracellular Ca²⁺ entry which affected downstream events such as activation of PKC, PKA, intracellular Ca²⁺ release, and activation of nitric oxide synthase. Quercetin relaxed cholecystokinin octapeptide and KCl-induced tension in a concentration dependent manner. Thus quercetin-induced relaxation was mediated by multiple signaling pathways.

The Resveratrol-induced Relaxation of Cholecystokinin Octapeptide- or KCl-induced Tension in Male Guinea Pig Gallbladder Strips Is Mediated Through L-type Ca2+Channels

Background/Aims

Resveratrol (3,5,4′-trihydroxystilbene) is a polyphenolic compound (stilbene) and a phytoalexin. The purpose of this study was to determine the mechanism which mediated the resveratrol-induced relaxation of cholecystokinin octapeptide- or KCl-induced tension in male guinea pig gallbladder strips.

Methods

Gallbladder strips were prepared and suspended in in vitro chambers filled with Krebs-Henseleit solution. The strips were attached to force displacement transducers, and the changes in tension were recorded on a polygraph. All reagents were added directly into the chambers.

Results

To determine if intracellular Ca²⁺ release mediated the resveratrol-induced relaxation of cholecystokinin octapeptide-induced tension, 2-aminoethoxydiphenylborane (2-APB) was used. 2-APB significantly (P < 0.01) decreased the amount of RSVL-induced relaxation. To determine if protein kinase A (PKA) mediated the resveratrol-induced relaxation, PKA inhibitor 14-22 amide myristolated (PKA-IM) was used. PKA-IM had no effect on resveratrol-induced relaxation. Neither KT5823, N^G-methyl-L-arginine acetate salt, a nitric oxide synthase inhibitor, nor fulvestrant had a significant effect on the amount of resveratrol-induced relaxation. Genistein, a protein tyrosine kinase inhibitor, significantly (P < 0.01) increased the RSVL-induced relaxation. To determine if protein kinase C mediated the RSVL-induced relaxation, the protein kinase C inhibitors bisindolymaleimide IV and chelerythrine Cl- were used together, and a significant (P < 0.05) increase in resveratrol-induced relaxation was observed. The pretreatment of the strips with resveratrol significantly (P < 0.001) decreased the amount of KCl- and cholecystokinin octapep-tide-induced tension.

Conclusions

Resveratrol-induced relaxation is mediated by its effects on L-type Ca²⁺ channels and intracellular Ca²⁺ release.

Strategies for the real-time detection of Ca2+ channel events of single cells: recent advances and new possibilities

Ca(2+) ion channels play key roles in cell physiology and they are important drug targets. The Ca(2+) channel events are mainly measurable by fluorescent and patch clamp methods. This review summarizes the recent advances of these techniques for the detection of Ca(2+) channel events and the prospect of their new directions in the near future. Conventional bulk fluorescent methods are amenable to high-throughput applications, but they are not real-time single-cell measurements, which provide kinetic data on individual cells and offer unparalleled sensitive data for rare cells. Recent advances on real-time single-cell fluorescent measurements are conducted on microfluidic chips with scalable cell-retention sites, integrated with electrical stimulation and fluorescent measuring features. Patch clamp techniques are real-time measurements conducted on single cells, but the measurements are of low throughput. Recent advances are conducted on microfluidic patch clamp chips for high-throughput applications. Future real-time single-cell Ca(2+) channel event measurements will be conducted in a multiparametric manner in an integrated and automated microfluidic chip.

Progesterone inhibits L-type calcium currents in gallbladder smooth muscle cells

BACKGROUND AND AIM

The incidence of gallbladder stones is higher in women during pregnancy than in men. Progesterone can inhibit gallbladder motility and facilitate gallstone formation. However, the ionic mechanisms have not been fully illuminated. This study sought to investigate the effects of progesterone on L-type calcium currents and voltage-dependent potassium currents in gallbladder smooth muscle cells.

METHODS

Gallbladder smooth muscle cells were isolated by enzymatic digestion from adult guinea pigs. Ionic currents were recorded by the whole-cell patch clamp method.

RESULTS

Progesterone inhibited L-type calcium currents in a concentration-dependent manner. The characteristic of current-voltage curve was not significantly altered. The amplitude of calcium currents was gradually suppressed, reached a steady-state level within 4-6 min, and restored partly after washout. In the presence of protein kinase A (PKA) inhibitor, Rp-cAMP, the inhibitory effect induced by progesterone was apparently attenuated, whereas forskolin, a direct activator of adenylate cyclase, could suppress L-type calcium channel. However, progesterone did not significantly affect voltage-dependent potassium currents.

CONCLUSIONS

Progesterone inhibits L-type calcium channel by cAMP/PKA pathway in gallbladder smooth muscle cells. This may be an important mechanism for the gallbladder hypomotility induced by progesterone.

Mechanisms mediating CCK-8S-induced contraction of proximal colon in guinea pigs

AIM: To investigate the effects of sulfated cholecystokinin octapeptide (CCK-8S) on the contractile activity of guinea-pig proximal colon.

METHODS: Proximal colonic smooth muscle (PCSM) strips were obtained from adult female guinea pigs and contractile response of PCSM strips was recorded using a polyphysiograph. PCSM cells were isolated by enzymatic digestion. Resting potential (RP), action potential (AP), large conductance potassium channel currents (I_BKCa) and L-type calcium currents (I_Ca-L) were recorded by patch-clamp techniques.

RESULTS: (1) CCK-8S (10^-7 mol/L) enhanced the mean contractile amplitude of colonic circular muscle and longitudinal muscle (LM) strips by 56.53% ± 11.92% (P = 0.038) and 65.93% ± 12.98% (P = 0.019), respectively, as well as the mean frequency of LM by 31.69% ± 13.58% (P = 0.023), which were significantly attenuated by pretreating strips with devazepide, nifedipine, iberiotoxin, thapsigargin (TG) and BAPTA-AM (BA) respectively; (2) CCK-8S (10^-7 mol/L) increased the AP amplitude by 38.6% ± 3.2% (P = 0.015), decreased AP duration by 36.9% ± 8.7% (P = 0.026), and depolarized the RP from -61.3 ± 2.7 mV to -29.8 ± 5.9 mV (P = 0.032); and (3) Compared with the normal control group, CCK-8S (10^-7 mol/L) enhanced the peak current of I_BKCa by 18.7% ± 2.1% (from 916 ± 183 pA to 1088 ± 226 pA; at +60 mV; P = 0.029), which was inhibited by respective pretreatment with iberiotoxin and devazepide. Additionally, CCK-8S (10^-7 mol/L) intensified the peak current of I_Ca-L by 40% (from 60 ± 8 pA to 84 ± 11 pA; at +10 mV; P = 0.012), compared to the normal control group, which was apparently suppressed by respective pretreatment with nifedipine, devazepide, TG and BA. In the respective presence of heparin and staurosporine, CCK-8S did not significantly enhance I_BKCa and I_Ca-L.

CONCLUSION: The results suggest that CCK-8S promotes guinea-pig proximal colon contraction by CCK1 receptors, following activation of the inositol triphosphate-protein kinase C signal transduction pathway.

Emodin augments calcium activated chloride channel in colonic smooth muscle cells by Gi/Go protein

Emodin is a natural anthraquinone in rhubarb. It has been identified as a prokinetic drug for gastrointestinal motility in Chinese traditional medicine. Emodin contracts smooth muscle by increasing the concentration of intracellular Ca(2+). In many smooth muscles, increasing intracellular Ca(2+) activates Ca(2+)-activated Cl(-) channels (ClCA). The study was aimed to investigate the effects of emodin on ClCA channels in colonic smooth muscle. 4 channel physiology signal acquire system was used to measure isometric contraction of smooth muscle strips. ClCA currents were recorded by EPC10 with perforated whole cell model. Emodin contracted strips and cells in colonic smooth muscle and augmented ClCA currents. Niflumic acid (NFA) and 4', 4'-diisothiostilbene-2, 2-disulfonic acid (DIDS) blocked the effects. Gi/Go protein inhibits protein kinase A (PKA) and protein kinase C (PKC), and PKA and PKC reduced ClCA currents. Pertussis toxin (PTX, a special inhibitor of Gi/Go protein), 8-bromoadenosine 38, 58-cyclic monophosphate (8-BrcAMP, a membrane-permeant protein kinase A activator) and Phorbol-12-myristate-13-acetate (PMA, a membrane-permeant protein kinase C activator) inhibited the effects on ClCA currents significantly. Our findings suggest that emodin augments ClCA channels to contract smooth muscle in colon, and the effect is induced mostly by enhancement of membrane Gi/Go protein signal transducer pathway.