Effects of Ca2+ channel blockers on store-operated Ca2+ channel currents of Kupffer cells after hepatic ischemia/reperfusion injury in rats

Role of TRP Channels in Liver-Related Diseases

The liver plays a crucial role in preserving the homeostasis of an entire organism by metabolizing both endogenous and exogenous substances, a process that relies on the harmonious interactions of hepatocytes, hepatic stellate cells (HSCs), Kupffer cells (KCs), and vascular endothelial cells (ECs). The disruption of the liver's normal structure and function by diverse pathogenic factors imposes a significant healthcare burden. At present, most of the treatments for liver disease are palliative in nature, rather than curative or restorative. Transient receptor potential (TRP) channels, which are extensively expressed in the liver, play a crucial role in regulating intracellular cation concentration and serve as the origin or intermediary stage of certain signaling pathways that contribute to liver diseases. This review provides an overview of recent developments in liver disease research, as well as an examination of the expression and function of TRP channels in various liver cell types. Furthermore, we elucidate the molecular mechanism by which TRP channels mediate liver injury, liver fibrosis, and hepatocellular carcinoma (HCC). Ultimately, the present discourse delves into the current state of research and extant issues pertaining to the targeting of TRP channels in the treatment of liver diseases and other ailments. Despite the numerous obstacles encountered, TRP channels persist as an extremely important target for forthcoming clinical interventions aimed at treating liver diseases.

TRPM2 Non-Selective Cation Channels in Liver Injury Mediated by Reactive Oxygen Species

TRPM2 channels admit Ca²⁺ and Na⁺ across the plasma membrane and release Ca²⁺ and Zn²⁺ from lysosomes. Channel activation is initiated by reactive oxygen species (ROS), leading to a subsequent increase in ADP-ribose and the binding of ADP-ribose to an allosteric site in the cytosolic NUDT9 homology domain. In many animal cell types, Ca²⁺ entry via TRPM2 channels mediates ROS-initiated cell injury and death. The aim of this review is to summarise the current knowledge of the roles of TRPM2 and Ca²⁺ in the initiation and progression of chronic liver diseases and acute liver injury. Studies to date provide evidence that TRPM2-mediated Ca²⁺ entry contributes to drug-induced liver toxicity, ischemia–reperfusion injury, and the progression of non-alcoholic fatty liver disease to cirrhosis, fibrosis, and hepatocellular carcinoma. Of particular current interest are the steps involved in the activation of TRPM2 in hepatocytes following an increase in ROS, the downstream pathways activated by the resultant increase in intracellular Ca²⁺, and the chronology of these events. An apparent contradiction exists between these roles of TRPM2 and the role identified for ROS-activated TRPM2 in heart muscle and in some other cell types in promoting Ca²⁺-activated mitochondrial ATP synthesis and cell survival. Inhibition of TRPM2 by curcumin and other “natural” compounds offers an attractive strategy for inhibiting ROS-induced liver cell injury. In conclusion, while it has been established that ROS-initiated activation of TRPM2 contributes to both acute and chronic liver injury, considerable further research is needed to elucidate the mechanisms involved, and the conditions under which pharmacological inhibition of TRPM2 can be an effective clinical strategy to reduce ROS-initiated liver injury.

Sevoflurane protects the liver from ischemia-reperfusion injury by regulating Nrf2/HO-1 pathway

We aimed to investigate the role and mechanism of sevoflurane (SEV) preconditioning in liver ischemia-reperfusion (I/R) injury. In vivo, rats were randomly divided into Sham group, I/R rat model group, I/R + SEV group and SEV group. In vitro, hypoxia-reoxygenation (H/R) cell model were established. Hematoxylin-Eosin (H&E) and TUNEL assay were used to evaluate the degree of tissue damage and detect apoptosis in rats, respectively. HO-1, nuclear Nrf2 and cytosolic Nrf2 expressions were detected by immunohistochemical staining, Western blot analysis and quantitative real-time PCR (qRT-PCR), respectively. Contents of Lactate dehydrogenase (LDH), malondialdehyde (MDA), and reactive oxygen species (ROS) were determined by corresponding kits. Inflammatory factor levels, cell viability, apoptosis were detected by enzyme-linked immunosorbent assay (ELISA), MTT assay, and flow cytometry, respectively.In the I/R group, liver damage was severe, apoptosis-positive cells were increased, HO-1 and nuclear Nrf2 expressions were increased, and cytosolic Nrf2 expression was decreased. After SEV pretreatment, the degree of liver injury and apoptosis in rats were significantly reduced, HO-1 and nuclear Nrf2 expressions were increased significantly, and cytosolic Nrf2 expression was decreased. 4% SEV had the best mitigating effect on H/R-induced liver cell damage, as evidenced by reduced contents of LDH and MDA, decreased inflammatory factors, a lowered apoptosis rate, inhibited ROS production, effectively promoted Nrf2 nucleation, and activated Nrf/HO-1 pathway. ML385 pretreatment significantly inhibited the effect of SEV on hepatocytes.Sevoflurane protects the liver from ischemia-reperfusion injury by regulating the Nrf2/HO-1 pathway.

Mechanism of a methylxanthine drug theophylline-induced Ca2+ signaling and cytotoxicity in AML12 mouse hepatocytes

Theophylline is a methylxanthine drug used in therapy for respiratory diseases. However, the impact of theophylline on Ca²⁺ signaling has not been explored in liver cells. This study examined whether theophylline affected Ca²⁺ homeostasis and its related cytotoxicity in AML12 mouse hepatocytes. Cell viability was measured by the cell viability reagent (WST-1). Cytosolic Ca²⁺ concentration ([Ca²⁺]_i) was measured by the Ca²⁺-sensitive fluorescent dye fura-2. Theophylline (25-125 μM) induced [Ca²⁺]_i rises and cause cytotoxicity in AML12 cells. This cytotoxic response was reversed by chelation of cytosolic Ca²⁺ with BAPTA/AM. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin abolished theophylline-induced [Ca²⁺]_i rises. Conversely, treatment with theophylline also abolished thapsigargin-induced [Ca²⁺]_i rises. However, inhibition of PLC failed to alter theophylline-evoked [Ca²⁺]_i rises. In Ca²⁺-containing medium, modulators of store-operated Ca²⁺ channels inhibited 30% of the [Ca²⁺]_i rises, whereas the PKC modulators had no effect. Furthermore, theophylline-induced Ca²⁺ influx was confirmed by Mn²⁺-induced quench of fura-2 fluorescence. Together, in AML12 cells, theophylline caused Ca²⁺-associated cytotoxicity and induced Ca²⁺ entry through PLC-independent Ca²⁺ release from the endoplasmic reticulum and PKC-insensitive store-operated Ca²⁺ channels. BAPTA-AM with its protective effects may be a potential compound for prevention of theophylline-induced cytotoxicity.

Interaction Mechanisms Between Major Depressive Disorder and Non-alcoholic Fatty Liver Disease

Major depressive disorder (MDD), which is highly associated with non-alcoholic fatty liver disease (NAFLD), has complex pathogenic mechanisms. However, a limited number of studies have evaluated the mutual pathomechanisms involved in MDD and NAFLD development. Chronic stress-mediated elevations in glucocorticoid (GC) levels play an important role in the development of MDD-related NAFLD. Elevated GC levels can induce the release of inflammatory factors and changes in gut permeability. Elevated levels of inflammatory factors activate the hypothalamic-pituitary-adrenal (HPA) axis, which further increases the release of GC. At the same time, changes in gut permeability promote the release of inflammatory factors, which results in a vicious circle among the three, causing disease outbreaks. Even though the specific role of the thyroid hormone (TH) in this pathogenesis has not been fully established, it is highly correlated with MDD and NAFLD. Therefore, changing lifestyles and reducing psychological stress levels are necessary measures for preventing MDD-related NAFLD. Among them, GC inhibitors and receptor antagonists may be key in the alleviation of early and mid-term disease progression. However, combination medications may be important in late-stage diseases, but they are associated with various side effects. Traditional Chinese medicines have been shown to be potential therapeutic alternatives for such complex diseases.

Exploration of thioridazine-induced Ca2+ signaling and non-Ca2+-triggered cell death in HepG2 human hepatocellular carcinoma cells

Thioridazine, belonging to first-generation antipsychotic drugs, is a prescription used to treat schizophrenia. However, the effect of thioridazine on intracellular Ca²⁺ concentration ([Ca²⁺]_i) and viability in human liver cancer cells is unclear. This study examined whether thioridazine altered Ca²⁺ signaling and viability in HepG2 human hepatocellular carcinoma cells. Ca²⁺ concentrations in suspended cells were measured using the fluorescent Ca²⁺-sensitive dye fura-2. Cell viability was examined by WST-1 assay. Thioridazine at concentrations of 25-100 μM induced [Ca²⁺]_i rises. Ca²⁺ removal reduced the signal by 20%. Thioridazine (100 μM) induced Mn²⁺ influx suggesting of Ca²⁺ entry. Thioridazine-induced Ca²⁺ entry was inhibited by 20% by protein kinase C (PKC) activator (phorbol 12-myristate 13 acetate) and inhibitor (GF109203X) and by three inhibitors of store-operated Ca²⁺ channels: nifedipine, econazole, and SKF96365. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin (TG) abolished thioridazine-evoked [Ca²⁺]_i rises. On the other hand, thioridazine preincubation completely inhibited the [Ca²⁺]_i rises induced by TG. Furthermore, U73122 totally suppressed the [Ca²⁺]_i rises induced by thioridazine via inhibition of phospholipase C (PLC). Regarding cytotoxicity, at 30-80 μM, thioridazine reduced cell viability in a concentration-dependent fashion. This cytotoxicity was not prevented by preincubation with 1,2-bis (2-aminophenoxy) ethane-N, N, N', N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM) (a Ca²⁺ chelator). To conclude, thioridazine caused concentration-dependent [Ca²⁺]_i rises in HepG2 human hepatoma cells by inducing Ca²⁺ release from the endoplasmic reticulum via PLC-associated pathways and Ca²⁺ influx from extracellular medium through PKC-sensitive store-operated Ca²⁺ entry. In addition, thioridazine induced cytotoxicity in a Ca²⁺-independent manner.

Mechanisms underlying the effect of an oral antihyperglycaemic agent glyburide on calcium ion (Ca2+ ) movement and its related cytotoxicity in prostate cancer cells

Glyburide is an agent commonly used to treat type 2 diabetes and also affects various physiological responses in different models. However, the effect of glyburide on Ca²⁺ movement and its related cytotoxicity in prostate cancer cells is unclear. This study examined whether glyburide altered Ca²⁺ signalling and viability in PC3 human prostate cancer cells and investigated those underlying mechanisms. Intracellular Ca²⁺ concentrations ([Ca²⁺ ]_i ) in suspended cells were measured by using the fluorescent Ca²⁺ -sensitive dye fura-2. Cell viability was examined by WST-1 assay. Glyburide at concentrations of 100-1000 μM induced [Ca²⁺ ]_i rises. Ca²⁺ removal reduced the signal by approximately 60%. In Ca²⁺ -containing medium, glyburide-induced Ca²⁺ entry was inhibited by 60% by protein kinase C (PKC) activator (phorbol 12-myristate 13 acetate, PMA) and inhibitor (GF109203X), and modulators of store-operated Ca²⁺ channels (nifedipine, econazole and SKF96365). Furthermore, glyburide induced Mn²⁺ influx suggesting of Ca²⁺ entry. In Ca²⁺ -free medium, inhibition of phospholipase C (PLC) with U73122 significantly inhibited glyburide-induced [Ca²⁺ ]_i rises. Treatment with the endoplasmic reticulum (ER) Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) abolished glyburide-evoked [Ca²⁺ ]_i rises. Conversely, treatment with glyburide abolished BHQ-evoked [Ca²⁺ ]_i rises. Glyburide at 100-500 μM decreased cell viability, which was not reversed by pretreatment with the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Together, in PC3 cells, glyburide induced [Ca²⁺ ]_i rises by Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ channels and Ca²⁺ release from the ER in a PLC-dependent manner. Glyburide also caused Ca²⁺ -independent cell death. This study suggests that glyburide could serve as a potential agent for treatment of prostate cancer.

Na-K-2Cl Cotransporter and Store-Operated Ca2+ Entry in Pacemaking by Interstitial Cells of Cajal

Pacemaker depolarization in interstitial cells of Cajal (ICCs) is believed to be induced by Ca²⁺ transients and activation of anoctamin-1 (Ano1) channels in the plasma membrane. However, block of store-operated calcium entry (SOCE) or the Na-K-2Cl cotransporter (NKCC1) terminates pacemaker activity in ICC, indicating these transporters are involved in the initiation or maintenance of pacemaker activity. We hypothesized that SOCE contributes to pacemaker depolarization by maintaining [Ca²⁺] in the endoplasmic reticulum, which is the underlying source of Ca²⁺ transients for activation of Ano1. NKCC1 maintains the Cl^- gradient supporting the driving force for inward current mediated by Ano1. Currently mechanisms sustaining release of Ca²⁺ and activation of Ano1 channels during the plateau phase of slow waves are unknown, but the reverse mode of the Na⁺/Ca²⁺ exchange may contribute. We generated a mathematical model of pacemaker activity based on current empirical observations from ICC of mouse small intestine that incorporates functions of SOCE and NKCC1. This model reproduces experimental findings, suggesting roles for SOCE and Ano1 channels: blocking of either NKCC1 or SOCE in our model terminates pacemaker activity. Direct contribution of NKCC1 to pacemaker activity in a beat-to-beat manner is not predicted by our model. Instead, NKCC1 plays a maintenance role supporting the driving force for Cl^- efflux. Incorporation of SOCE allows the model to drive pacemaker activity without a diastolic depolarization, as observed in cardiac pacemaking. Further biological experiments are necessary to validate and further refine the roles of NKCC1, Na⁺/Ca²⁺ exchange, and Ano1 in the pacemaker mechanism of ICC.

Kcne4 deletion sex dependently inhibits the RISK pathway response and exacerbates hepatic ischemia-reperfusion injury in mice

Activation of antiapoptotic signaling cascades, such as the reperfusion injury salvage kinase (RISK) and survivor activating factor enhancement (SAFE) pathways, is protective in a variety of tissues in the context of ischemia-reperfusion (IR) injury. Hepatic IR injury causes clinically significant hepatocellular damage in surgical procedures, including liver transplantation and hepatic resection, increasing associated morbidity and mortality. We previously found that the cardiovascular-expressed K⁺ voltage-gated channel ancillary subunit KCNE4 sex specifically influences the cardiac RISK/SAFE pathway response to IR and that Kcne4 deletion testosterone dependently exacerbates cardiac IR injury. Here, we discovered that germline Kcne4 deletion exacerbates hepatic IR injury damage in 13-mo-old male mice, despite a lack of Kcne4 expression in male mouse liver. Examining RISK/SAFE pathway induction, we found that Kcne4 deletion prevents the hepatic ERK1/2 phosphorylation response to IR injury. Conversely, in 13-mo-old female mice, Kcne4 deletion increased both baseline and post-IR GSK-3β inhibitory phosphorylation, and pharmacological GSK-3β inhibition was hepatoprotective. Finally, castration of male mice restored normal hepatic RISK/SAFE pathway responses in Kcne4^-/- mice, eliminated Kcne4 deletion-dependent serum alanine aminotransferase elevation, and genotype independently augmented the hepatic post-IR GSK-3β phosphorylation response. These findings support a role for KCNE4 as a systemic modulator of IR injury response and uncover hormonally influenced, sex-specific, KCNE4-dependent and -independent RISK/SAFE pathway induction.

Metformin Reduces Lipotoxicity-Induced Meta-Inflammation in β-Cells through the Activation of GPR40-PLC-IP3 Pathway

BACKGROUND AND PURPOSE

Metformin, a widely used antidiabetic drug, has been shown to have anti-inflammatory properties; nevertheless, its influence on β-cell meta-inflammation remains unclear. The following study investigated the effects of metformin on meta-inflammatory in β-cells and whether the underlying mechanisms were associated with the G protein-coupled receptor 40-phospholipase C-inositol 1, 4, 5-trisphosphate (GPR40-PLC-IP3) pathway.

MATERIALS AND METHODS

Lipotoxicity-induced β-cells and the high-fat diet-induced obese rat model were used in the study.

RESULTS

Metformin-reduced lipotoxicity-induced β-cell meta-inflammatory injury was associated with the expression of GPR40. GPR40 was involved in metformin reversing metabolic inflammation key marker TLR4 activation-mediated β-cell injury. Furthermore, downstream signaling protein PLC-IP3 of GPR40 was involved in the protective effect of metformin on meta-inflammation, and the above process of metformin was partially regulated by AMPK activity. In addition, the anti-inflammatory effects of metformin were observed in obese rats.

CONCLUSION

Metformin can reduce lipotoxicity-induced meta-inflammation in β-cells through the regulation of the GPR40-PLC-IP3 pathway and partially via the regulation of AMPK activity.

Hepatic ischemia-reperfusion injury in liver transplant setting: mechanisms and protective strategies

Hepatic ischemia-reperfusion injury is a major cause of liver transplant failure, and is of increasing significance due to increased use of expanded criteria livers for transplantation. This review summarizes the mechanisms and protective strategies for hepatic ischemia-reperfusion injury in the context of liver transplantation. Pharmacological therapies, the use of pre-and post-conditioning and machine perfusion are discussed as protective strategies. The use of machine perfusion offers significant potential in the reconditioning of liver grafts and the prevention of hepatic ischemia-reperfusion injury, and is an exciting and active area of research, which needs more study clinically.

Acetylcholine-induced Ciliary Beat of the Human Nasal Mucosa Is Regulated by the Pannexin-1 Channel and Purinergic P2X Receptor

Background Airway mucociliary transport is an important function for the clearance of inhaled foreign particulates in the respiratory tract. The present study aimed at investigating the regulatory mechanism of acetylcholine (Ach)-induced ciliary beat of the human nasal mucosa in ex vivo. Methods The inferior turbinate mucosa was collected from patients with chronic hypertrophic rhinitis during endoscopic surgery. The mucosa was cut into thin strips, and ciliary movement was observed under a phase-contrast light microscope with a high-speed digital video camera. The sample was alternatively subjected to scanning electron microscopic observation. Results Cilia on the turbinate epithelium were well preserved at the ultrastructural level. The baseline ciliary beat frequency (CBF) was 6.45 ± 0.32 Hz. CBF was significantly increased by stimulation with 100 µM Ach and 100 µM adenosine triphosphate. The Ach-induced CBF increase was completely inhibited by removing extracellular Ca²⁺. Significant inhibition of the Ach-induced CBF was also observed by the addition of 1 µM atropine, 40 µM 2-aminoethoxydiphenyl borate (inositol trisphosphate [IP₃] receptor antagonist), 10 µM carbenoxolone (pannexin-1 blocker), 1 mM probenecid (pannexin-1 blocker), 100 µM pyridoxalphosphate-6-azophenyl-20,40-disulfonic acid (P2X antagonist), and 300 µM flufenamic acid (connexin blocker). Meanwhile, 30 nM bafilomycin A1 (vesicular transport inhibitor) did not inhibit the Ach-induced CBF increase.

CONCLUSIONS

These results indicate that the regulatory mechanism of the Ach-induced ciliary beat is dependent on extracellular Ca²⁺ and involves the muscarinic Ach receptor, IP₃ receptor, pannexin-1 channel, purinergic P2X receptor, and connexin channel. We proposed a tentative intracellular signaling pathway of the Ach-induced ciliary beat, in which the pannexin-1-P2X unit may play a central role in ciliary beat regulation.

The effect of magnolol on Ca2+ homeostasis and its related physiology in human oral cancer cells

OBJECTIVE

Magnolol, a polyphenol compound from herbal medicines, was shown to alter physiology in various cell models. However, the effect of magnolol on Ca²⁺ homeostasis and its related physiology in oral cancer cells is unclear. This study examined whether magnolol altered Ca²⁺ signaling and cell viability in OC2 human oral cancer cells.

METHODS

Cytosolic Ca²⁺ concentrations ([Ca²⁺]_i) in suspended cells were measured by using the fluorescent Ca²⁺-sensitive dye fura-2. Cell viability was examined by 4-[3-[4-lodophenyl]-2-4(4-nitrophenyl)-2H-5-tetrazolio-1,3-benzene disulfonate] water soluble tetrazolium-1 (WST-1) assay.

RESULTS

Magnolol at concentrations of 20-100 μM induced [Ca²⁺]_i rises. Ca²⁺ removal reduced the signal by approximately 50%. Magnolol (100 μM) induced Mn²⁺ influx suggesting of Ca²⁺ entry. Magnolol-induced Ca²⁺ entry was partially suppressed by protein kinase C (PKC) regulators, and inhibitors of store-operated Ca²⁺ channels. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) abolished magnolol-evoked [Ca²⁺]_i rises. Conversely, treatment with magnolol abolished BHQ-evoked [Ca²⁺]_i rises. Inhibition of phospholipase C (PLC) with U73122 partially inhibited magnolol-induced [Ca²⁺]_i rises. Magnolol at 20-100 μM decreased cell viability, which was not reversed by pretreatment with the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM).

CONCLUSIONS

Together, in OC2 cells, magnolol induced [Ca²⁺]_i rises by evoking partially PLC-dependent Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ entry. Magnolol also caused Ca²⁺-independent cell death. Therefore, magnolol-induced cytotoxicity may not be involved in activation mechanisms associated with intracellular Ca²⁺ mobilization in oral cancer cells.

Effect of tetramethylpyrazine (TMP) on Ca2+ signal transduction and cell viability in a model of renal tubular cells

Tetramethylpyrazine (TMP) is a compound purified from herb. Its effect on Ca²⁺ concentrations ([Ca²⁺ ]_i ) in renal cells is unclear. This study examined whether TMP altered Ca²⁺ signaling in Madin-Darby canine kidney (MDCK) cells. TMP at 100-800 μM induced [Ca²⁺ ]_i rises, which were reduced by Ca²⁺ removal. TMP induced Mn²⁺ influx implicating Ca²⁺ entry. TMP-induced Ca²⁺ entry was inhibited by 30% by modulators of protein kinase C (PKC) and store-operated Ca²⁺ channels. Treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) inhibited 93% of TMP-evoked [Ca²⁺ ]_i rises. Treatment with TMP abolished BHQ-evoked [Ca²⁺ ]_i rises. Inhibition of phospholipase C (PLC) abolished TMP-induced responses. TMP at 200-1000 μM decreased viability, which was not reversed by pretreatment with the Ca²⁺  chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester. Together, in MDCK cells, TMP induced [Ca²⁺ ]_i rises by evoking PLC-dependent Ca²⁺ release from endoplasmic reticulum and Ca²⁺ entry via PKC-sensitive store-operated Ca²⁺ entry. TMP also caused Ca²⁺ -independent cell death.

Effects of puerarin on intracellular Ca2+ and cell viability of MDCK renal tubular cells

Puerarin is a natural compound and has been used as herb medication in a number of countries, especially in Asia. The effect of puerarin on Ca²⁺ signaling is unknown in renal cells. This study examined whether puerarin affected Ca²⁺ physiology in MDCK renal tubular cells. Cytosolic free Ca²⁺ levels ([Ca²⁺]_i) were measured using the fluorescent dye fura-2. Cell viability was examined by using WST-1 assay. Puerarin induced [Ca²⁺]_i rises and the response was reduced by removing extracellular Ca²⁺. Puerarin-induced Ca²⁺ entry was not altered by protein kinase C (PKC) activity, but was inhibited by nifedipine. In Ca²⁺-free medium, treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) or thapsigargin partly inhibited puerarin-evoked [Ca²⁺]_i rises. Inhibition of phospholipase C (PLC) with U73122 did not change puerarin-induced [Ca²⁺]_i rises. Puerarin at 25-50μM caused cytotoxicity, which was not reversed by pretreatment with the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Collectively, in MDCK cells, puerarin induced [Ca²⁺]_i rises by evoking PLC-independent Ca²⁺ release from the endoplasmic reticulum and other unknown stores, and Ca²⁺ entry via nifedipine-sensitive, PKC-insensitive Ca²⁺ entry pathways. Puerarin also caused Ca²⁺-independent cell death.

Amitriptyline modulated Ca2+ signaling and induced Ca2+-independent cell viability in human osteosarcoma cells

Amitriptyline is a widely used tricyclic antidepressant, which acts primarily as a serotonin–norepinephrine reuptake inhibitor. This study examined the effect of amitriptyline on Ca2+ homeostasis and its related mechanism in MG63 human osteosarcoma cells. Amitriptyline evoked cytosolic-free Ca2+ concentrations ([Ca2+]i) rises concentration dependently. Amitriptyline-evoked Ca2+ entry was confirmed by Mn2+-induced quench of fura-2 fluorescence. This entry was inhibited by Ca2+ entry modulators nifedipine, econazole, SKF96365, the protein kinase C (PKC) activator phorbol 12-myristate 13 acetate but was not affected by the PKC inhibitor GF109203X. In Ca2+-free medium, treatment with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin (TG) inhibited amitriptyline-evoked [Ca2+]i rises by 95%. Conversely, treatment with amitriptyline abolished TG-evoked [Ca2+]i rises. Inhibition of phospholipase C (PLC) with U73122 inhibited amitriptyline-evoked [Ca2+]i rises by 70%. Amitriptyline killed cells at 200–500 μM in a concentration-dependent fashion. Chelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid/AM did not reverse amitriptyline-induced cytotoxicity. Collectively, our data suggest that in MG63 cells, amitriptyline induced [Ca2+]i rises by evoking PLC-dependent Ca2+ release from the endoplasmic reticulum and Ca2+ entry via PKC-regulated store-operated Ca2+ entry. Amitriptyline also induced Ca2+-disassociated cell death.

The investigation of minoxidil-induced [Ca2+]i rises and non-Ca2+-triggered cell death in PC3 human prostate cancer cells

Minoxidil is clinically used to prevent hair loss. However, its effect on Ca²⁺ homeostasis in prostate cancer cells is unclear. This study explored the effect of minoxidil on cytosolic-free Ca²⁺ levels ([Ca²⁺]_i) and cell viability in PC3 human prostate cancer cells. Minoxidil at concentrations between 200 and 800 μM evoked [Ca²⁺]_i rises in a concentration-dependent manner. This Ca²⁺ signal was inhibited by 60% by removal of extracellular Ca²⁺. Minoxidil-induced Ca²⁺ influx was confirmed by Mn²⁺-induced quench of fura-2 fluorescence. Pre-treatment with the protein kinase C (PKC) inhibitor GF109203X, PKC activator phorbol 12-myristate 13 acetate (PMA), nifedipine and SKF96365 inhibited minoxidil-induced Ca²⁺ signal in Ca²⁺ containing medium by 60%. Treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-ditert-butylhydroquinone (BHQ) in Ca²⁺-free medium abolished minoxidil-induced [Ca²⁺]_i rises. Conversely, treatment with minoxidil abolished BHQ-induced [Ca²⁺]_i rises. Inhibition of phospholipase C (PLC) with U73122 abolished minoxidil-evoked [Ca²⁺]_i rises. Overnight treatment with minoxidil killed cells at concentrations of 200-600 μM in a concentration-dependent fashion. Chelation of cytosolic Ca²⁺ with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/AM (BAPTA/AM) did not prevent minoxidil's cytotoxicity. Together, in PC3 cells, minoxidil induced [Ca²⁺]_i rises that involved Ca²⁺ entry through PKC-regulated store-operated Ca²⁺ channels and PLC-dependent Ca²⁺ release from the endoplasmic reticulum. Minoxidil-induced cytotoxicity in a Ca²⁺-independent manner.

Effect of 2,5-dimethylphenol on Ca(2+) movement and viability in PC3 human prostate cancer cells

The phenolic compound 2,5-dimethylphenol is a natural product. 2,5-Dimethylphenol has been shown to affect rat hepatic and pulmonary microsomal metabolism. However, the effect of 2,5-dimethylphenol on Ca(2+ )signaling and cyotoxicity has never been explored in any culture cells. This study explored the effect of 2,5-dimethylphenol on cytosolic free Ca(2+ )levels ([Ca(2+)]i) and cell viability in PC3 human prostate cancer cells. 2,5-Dimethylphenol at concentrations between 500 μM and 1000 μM evoked [Ca(2+)]i rises in a concentration-dependent manner. This Ca(2+ )signal was inhibited by approximately half by the removal of extracellular Ca(2+). 2,5-Dimethylphenol-induced Ca(2+ )influx was confirmed by Mn(2+)-induced quench of fura-2 fluorescence. Pretreatment with the protein kinase C (PKC) inhibitor GF109203X, nifedipine or the store-operated Ca(2+ )entry inhibitors (econazole or SKF96365) inhibited 2,5-dimethylphenol-induced Ca(2+ )signal in Ca(2+)-containing medium by ∼30%. Treatment with the endoplasmic reticulum Ca(2+ )pump inhibitor thapsigargin in Ca(2+)-free medium abolished 2,5-dimethylphenol-induced [Ca(2+)]i rises. Conversely, treatment with 2,5-dimethylphenol abolished thapsigargin-induced [Ca(2+)]i rises. Inhibition of phospholipase C (PLC) with U73122 reduced 2,5-dimethylphenol-evoked [Ca(2+)]i rises by ∼80%. 2,5-Dimethylphenol killed cells at concentrations of 350-1000 μM in a concentration-dependent fashion. Chelation of cytosolic Ca(2+ )with 1,2-bis(2-aminophenoxy)ethane-N, N, N', N'-tetraacetic acid/AM (BAPTA/AM) did not prevent 2,5-dimethylphenol's cytotoxicity. Together, in PC3 cells, 2,5-dimethylphenol induced [Ca(2+)]i rises that involved Ca(2+ )entry through PKC-regulated store-operated Ca(2+ )channels and PLC-dependent Ca(2+ )release from the endoplasmic reticulum. 2,5-Dimethylphenol induced cytotoxicity in a Ca(2+)-independent manner.

Ca2+ Signaling and Cell Death Induced by Protriptyline in HepG2 Human Hepatoma Cells

The effect of protriptyline on Ca²⁺ physiology in human hepatoma is unclear. This study explored the effect of protriptyline on [Ca²⁺ ]_i and cytotoxicity in HepG2 human hepatoma cells. Protriptyline (50-150 μM) evoked [Ca²⁺ ]_i rises. The Ca²⁺ entry was inhibited by removal of Ca²⁺ . Protriptyline-induced Ca²⁺ entry was confirmed by Mn²⁺ -induced quench of fura-2 fluorescence. Except nifedipine, econazole, SKF96365, GF109203X, and phorbol 12-myristate 13 acetate did not inhibit Ca²⁺ entry. Treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) inhibited 40% of protriptyline-induced response. Treatment with protriptyline abolished BHQ-induced response. Inhibition of phospholipase C (PLC) suppressed protriptyline-evoked response by 70%. At 20-40 μM, protriptyline killed cells which was not reversed by the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Together, in HepG2 cells, protriptyline induced [Ca²⁺ ]_i rises that involved Ca²⁺ entry through nifedipine-sensitive Ca²⁺ channels and PLC-dependent Ca²⁺ release from endoplasmic reticulum. Protriptyline induced Ca²⁺ -independent cell death.

Naproxen-induced Ca2+ movement and death in MDCK canine renal tubular cells

Naproxen is an anti-inflammatory drug that affects cellular calcium ion (Ca(2+)) homeostasis and viability in different cells. This study explored the effect of naproxen on [Ca(2+)](i) and viability in Madin-Darby canine kidney cells (MDCK) canine renal tubular cells. At concentrations between 50 μM and 300 μM, naproxen induced [Ca(2+)](i) rises in a concentration-dependent manner. This Ca(2+) signal was reduced partly when extracellular Ca(2+) was removed. The Ca(2+) signal was inhibited by a Ca(2+) channel blocker nifedipine but not by store-operated Ca(2+) channel inhibitors (econazole and SKF96365), a protein kinase C (PKC) activator phorbol 12-myristate 13-acetate, and a PKC inhibitor GF109203X. In Ca(2+)-free medium, pretreatment with 2,5-di-tert-butylhydroquinone or thapsigargin, an inhibitor of endoplasmic reticulum Ca(2+) pumps, partly inhibited naproxen-induced Ca(2+) signal. Inhibition of phospholipase C with U73122 did not alter naproxen-evoked [Ca(2+)](i) rises. At concentrations between 15 μM and 30 μM, naproxen killed cells in a concentration-dependent manner, which was not reversed by prechelating cytosolic Ca(2+) with the acetoxymethyl ester of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl. Annexin V/propidium iodide staining data suggest that naproxen induced apoptosis. Together, in MDCK renal tubular cells, naproxen induced [Ca(2+)](i) rises by inducing Ca(2+) release from multiple stores that included the endoplasmic reticulum and Ca(2+) entry via nifedipine-sensitive Ca(2+) channels. Naproxen induced cell death that involved apoptosis.

Ca(2+) movement and apoptosis induced by deltamethrin in Madin-Darby canine kidney canine renal tubular cells

This study explored the effect of deltamethrin, a pesticide, on free Ca(2+) concentration [Ca(2+)]i, viability, and apoptosis in Madin-Darby canine kidney (MDCK) canine renal tubular cells. Deltamethrin at concentrations between 10μM and 40μM evoked [Ca(2+)]i rises in a concentration-dependent manner. The Ca(2+) entry was inhibited by nifedipine, econazole, phorbol 12-myristate 13-acetate, and SKF96365. Treatment with the endoplasmic reticulum Ca(2+) pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) in a Ca(2+)-free medium abolished deltamethrin-induced [Ca(2+)]i rise. Treatment with deltamethrin also abolished BHQ-induced [Ca(2+)]i rise. Inhibition of phospholipase C (PLC) activity with U73122 abolished deltamethrin-evoked [Ca(2+)]i rise. Deltamethrin killed cells at 30-60μM in a concentration-dependent manner. The cytotoxic effect of deltamethrin was not reversed by prechelating cytosolic Ca(2+) with the acetoxymethyl ester of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. Annexin V/propidium iodide staining data suggest that 30-50μM deltamethrin induced apoptosis. Together, in MDCK renal tubular cells, deltamethrin induced [Ca(2+)]i rises that involved Ca(2+) entry through protein kinase C-mediated store-operated Ca(2+) channels, and PLC-dependent Ca(2+) release from the endoplasmic reticulum. Deltamethrin also induced Ca(2+)-independent cell death that might involve apoptosis.

Effect of deoxycholic acid on Ca2+ movement, cell viability and apoptosis in human gastric cancer cells

Deoxycholic acid (DOA) is one of the secondary bile acids used as a mild detergent for the isolation of membrane associated proteins. This study examined whether the secondary bile acid, DOA, altered Ca(2+) movement, cell viability and apoptosis in SCM1 human gastric cancer cells. The Ca(2+)-sensitive fluorescent dye fura-2 was used to measure [Ca(2+)]i. DOA-evoked [Ca(2+)]i rises concentration dependently. The response was reduced by removing extracellular Ca(2+). DOA-evoked Ca(2+) entry was inhibited by store-operated Ca(2+) channel inhibitors (nifedipine, econazole and SKF96365), the protein kinase C (PKC) activator phorbol 12-myristate 13 acetate (PMA) and the PKC inhibitor GF109203X. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin (TG) abolished DOA-evoked [Ca(2+)]i rises. Conversely, treatment with DOA abolished TG-evoked [Ca(2+)]i rises. Inhibition of phospholipase C with U73122 abolished DOA-evoked [Ca(2+)]i rises. At 100-500 μM, DOA decreased cell viability, which was not changed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). DOA between 100 and 300 μM also induced apoptosis. Collectively, in SCM1 cells, DOA-induced [Ca(2+)]i rises by evoking phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via store-operated Ca(2+) channels. DOA also caused Ca(2+)-independent apoptosis.

Effect of melamine on [Ca(2+)]i and viability in PC3 human prostate cancer cells

Melamine is thought to be an endocrine disrupter that affects physiology in cells. This study examined the effect of melamine on cytosolic free Ca(2+) concentrations ([Ca(2+)]i) and viability in PC3 human prostate cancer cells. Melamine evoked [Ca(2+)]i rises concentration-dependently. Melamine-evoked Ca(2+) entry was inhibited by nifedipine, econazole, SKF96365, GF109203X and phorbol 12-myristate 13 acetate. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin inhibited melamine-evoked [Ca(2+)]i rise. Conversely, treatment with melamine abolished thapsigargin-evoked [Ca(2+)]i rise. Inhibition of phospholipase C with U73122 did not alter melamine-evoked [Ca(2+)]i rise. Melamine at 500-800μM decreased cell viability, which was not reversed by pretreatment with the Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Collectively, our data suggest that in PC3 cells, melamine induced [Ca(2+)]i rises by evoking phospholipase C-independent Ca(2+) release from the endoplasmic reticulum, and Ca(2+) entry via protein kinase C-regulated store-operated Ca(2+) entry. Melamine also caused Ca(2+)-independent cell death.

The mechanism of honokiol-induced intracellular Ca(2+) rises and apoptosis in human glioblastoma cells

Honokiol, an active constituent of oriental medicinal herb Magnolia officinalis, caused Ca(2+) mobilization and apoptosis in different cancer cells. In vivo, honokiol crossed the blood-brain or -cerebrospinal fluid barrier, suggesting that it may be an effective drug for the treatment of brain tumors, including glioblastoma. This study examined the effect of honokiol on intracellular Ca(2+) concentration ([Ca(2+)]i) and apoptosis in DBTRG-05MG human glioblastoma cells. Honokiol concentration-dependently induced a [Ca(2+)]i rise. The signal was decreased partially by removal of extracellular Ca(2+). Honokiol-triggered [Ca(2+)]i rise was not suppressed by store-operated Ca(2+) channel blockers (nifedipine, econazole, SK&F96365) and the protein kinase C (PKC) activator phorbol 12-myristate 13 acetate (PMA), but was inhibited by the PKC inhibitor GF109203X. GF109203X-induced inhibition was not altered by removal of extracellular Ca(2+). In Ca(2+)-free medium, pretreatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin (TG) or 2,5-di-tert-butylhydroquinone (BHQ) abolished honokiol-induced [Ca(2+)]i rise. Conversely, incubation with honokiol abolished TG or BHQ-induced [Ca(2+)]i rise. Inhibition of phospholipase C (PLC) with U73122 abolished honokiol-induced [Ca(2+)]i rise. Honokiol (20-80μM) reduced the cell viability, which was not reversed by prechelating cytosolic Ca(2+) with BAPTA-AM (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester). Honokiol (20-60μM) enhanced reactive oxygen species (ROS) production, decreased mitochondrial membrane potential, released cytochrome c, and activated caspase-9/caspase-3. Together, honokiol induced a [Ca(2+)]i rise by inducing PLC-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via PKC-dependent, non store-operated Ca(2+) channels. Moreover, honokiol activated the mitochondrial pathway of apoptosis in DBTRG-05MG human glioblastoma cells.

Celecoxib-induced increase in cytosolic Ca(2+) levels and apoptosis in HA59T human hepatoma cells

Celecoxib has been shown to have antitumor effect in previous studies but the mechanisms are unclear. The effect of celecoxib on cytosolic Ca(2+) concentrations ([Ca(2+)]i) and viability in HA59T human hepatoma cells was explored. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)]i. Celecoxib at concentrations of 10-50 μM induced a [Ca(2+)]i rise in a concentration-dependent manner. The response was reduced by 80% by removing Ca(2+). Celecoxib induced Mn(2+) influx, leading to quenching of fura-2 fluorescence. Celecoxib-evoked Ca(2+) entry was suppressed by nifedipine, econazole, SK&F96365, and protein kinase C modulators. In the absence of extracellular Ca(2+), incubation with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin nearly abolished celecoxib-induced [Ca(2+)]i rise. Incubation with celecoxib abolished thapsigargin-induced [Ca(2+)]i rise. Inhibition of phospholipase C with U73122 abolished celecoxib-induced [Ca(2+)]i rise. At 1-50 μM, celecoxib inhibited cell viability by less than 20%, which was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N, N, N', N'-tetraacetic acid/acetoxy methyl (BAPTA/AM). Celecoxib (10-50 μM) also induced apoptosis. In sum, in HA59T hepatoma cells, celecoxib induced a [Ca(2+)]i rise by evoking phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via protein kinase C-sensitive store-operated Ca(2+) channels. Celecoxib also caused cell death via apoptosis.

Mechanisms of resveratrol-induced changes in cytosolic free calcium ion concentrations and cell viability in OC2 human oral cancer cells

Resveratrol is a natural compound that affects cellular calcium (Ca(2+)) homeostasis and viability in different cells. This study examined the effect of resveratrol on cytosolic free Ca(2+) concentrations ([Ca(2+)]i) and viability in OC2 human oral cancer cells. The Ca(2+)-sensitive fluorescent dye fura-2 was used to measure [Ca(2+)]i, and water-soluble tetrazolium-1 was used to measure viability. Resveratrol evoked concentration-dependent increase in [Ca(2+)]i. The response was reduced by removing extracellular Ca(2+). Resveratrol also caused manganese-induced fura-2 fluorescence quench. Resveratrol-evoked Ca(2+) entry was inhibited by nifedipine and the protein kinase C (PKC) inhibitor GF109203X but was not altered by econazole, SKF96365, and the PKC activator phorbol 12-myristate 13 acetate. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) abolished resveratrol-evoked [Ca(2+)]i rise. Conversely, treatment with resveratrol inhibited BHQ-evoked [Ca(2+)]i rise. Inhibition of phospholipase C (PLC) with U73122 abolished resveratrol-evoked [Ca(2+)]i rise. At 20-100 μM, resveratrol decreased cell viability, which was not affected by chelating cytosolic Ca(2+)with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester. Annexin V-fluorescein isothiocyanate staining data suggest that resveratrol at 20-40 μM induced apoptosis in a concentration-dependent manner. Collectively, in OC2 cells, resveratrol induced [Ca(2+)]i rise by evoking PLC-dependent Ca(2+) release from the endoplasmic reticulum and by causing Ca(2+) entry via nifedipine-sensitive, PKC-regulated mechanisms. Resveratrol also caused Ca(2+)-independent apoptosis.

The mechanism of bifonazole-induced [Ca(2+)]i rises and non-Ca(2+)-triggered cell death in PC3 human prostate cancer cells

Bifonazole is an antifungal drug widely used for treating skin diseases. The effect of bifonazole on physiology of cancer cells is unclear. The effect of bifonazole on cytosolic free Ca(2+) concentrations ([Ca(2+)]i) and viability in PC3 human prostate cancer cells was explored. The Ca(2+)-sensitive fluorescent dye, fura-2, was applied to measure [Ca(2+)]i. Bifonazole at concentrations of 5-30 µM induced a [Ca(2+)]i rise in a concentration-dependent manner. The response was reduced by 50% by removing extracellular Ca(2+). Bifonazole-evoked [Ca(2+)]i rise was not altered by nifedipine, econazole, SK&F96365 and protein kinase C activator, but was inhibited by 75% by GF109203X, a protein kinase C inhibitor. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) nearly abolished bifonazole-evoked [Ca(2+)]i rise. Conversely, treatment with bifonazole abolished BHQ-evoked [Ca(2+)]i rise. Inhibition of phospholipase C with U73122 abolished bifonazole-induced [Ca(2+)]i rise. At 30-100 µM, bifonazole decreased cell viability concentration-dependently, which was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N″,N'-tetraacetic acid/acetoxy methyl. Annexin V/propidium iodide staining data suggest that bifonazole (30-100 µM) induced apoptosis concentration-dependently. Together, in PC3 human prostate cancer cells, bifonazole induced [Ca(2+)]i rises by inducing phospholipase C- and protein kinase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) influx via non-store-operated pathways. Bifonazole induced cell death that might involve apoptosis.

Effect of the environmental pollutant bisphenol A dimethacylate (BAD) on Ca2+ movement and viability in OC2 human oral cancer cells

The environmental pollutant bisphenol A dimethacylate (BAD) has been used as a dental composite. The effect of BAD on cytosolic Ca(2+) concentrations ([Ca(2+)]i) and viability in OC2 human oral cancer cells was explored. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)]i. BAD induced [Ca(2+)]i rises in a concentration-dependent manner. The response was reduced by removing extracellular Ca(2+). BAD-evoked Ca(2+) entry was suppressed by nifedipine, econazole, and SK&F96365. In Ca(2+)-free medium, incubation with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin abolished BAD-induced [Ca(2+)]i rise. Inhibition of phospholipase C with U73122 did not alter BAD-induced [Ca(2+)]i rise. At 10-30μM, BAD inhibited cell viability, which was not reversed by chelating cytosolic Ca(2+). BAD (20-30μM) also induced apoptosis. Collectively, in OC2 cells, BAD induced a [Ca(2+)]i rise by evoking phospholipase C-independent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via store-operated Ca(2+) channels. BAD also caused apoptosis.

Effect of diindolylmethane on Ca2+ homeostasis and viability in MDCK renal tubular cells

The effect of the natural product diindolylmethane (DIM) on cytosolic Ca2+ concentrations ([Ca2+]i) and viability in MDCK renal tubular cells was explored. The Ca2+-sensitive fluorescent dye fura-2 was applied to measure [Ca2+]i. DIM at concentrations 1–50 μM induced a [Ca2+]i rise in a concentration-dependent manner. The response was reduced partly by removing Ca2+. DIM induced Mn2+ influx leading to quenching of fura-2 fluorescence. DIM-evoked Ca2+ entry was suppressed by nifedipine, econazole, SK&F96365 and protein kinase C modulators. In the absence of extracellular Ca2+, incubation with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin (TG) or 2,5-di-tert-butylhydroquinone (BHQ) greatly inhibited DIM-induced [Ca2+]i rise. Incubation with DIM abolished TG or BHQ-induced [Ca2+]i rise. Inhibition of phospholipase C with U73122 reduced DIM-induced [Ca2+]i rise by 50%. At 1, 10, 40 and 50 μM, DIM slightly enhanced cell proliferation. The effect of 50 μM DIM was reversed by chelating cytosolic Ca2+ with 1,2-bis(2-aminophenoxy)ethane- N, N, N', N'-tetraacetic acid. In sum, in MDCK cells, DIM induced a [Ca2+]i rise by evoking phospholipase C-dependent Ca2+ release from the endoplasmic reticulum and Ca2+ entry via protein kinase C-sensitive store-operated Ca2+ channels. DIM did not induce cell death.

Effect of sertraline on [Ca2+](i) and viability of human MG63 osteosarcoma cells

The antidepressant, sertraline, has been shown to have diverse in vitro effects. This study examined whether sertraline altered [Ca(2+)](i) in MG63 human osteosarcoma cells by using fura-2 as a Ca(2+)-sensitive fluorescent dye. At 50-200 µM, sertraline induced a [Ca(2+)](i) rise in a concentration-dependent manner. Ca(2+) response was decreased by removing extracellular Ca(2+), suggesting that Ca(2+) entry and release contributed to the [Ca(2+)](i) signal. Sertraline-induced Ca(2+) entry was inhibited by nifedipine, La(3+), Gd(3+), and SK&F96365. When extracellular Ca(2+) was removed, pretreatment with the endoplasmic reticulum (ER) Ca(2+) pump inhibitor, thapsigargin, or 2,5-di-tert-butylhydroquinone (BHQ) abolished the sertraline-evoked [Ca(2+)](i) rise. Incubation with sertraline also abolished the thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C (PLC) with U73122 abolished the sertraline-induced [Ca(2+)](i) rise. At 20-30 µM, overnight treatment with sertraline killed cells in a concentration-dependent manner. The cytotoxic effect of sertraline was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Annexin V/propidium iodide staining data demonstrate that sertraline (30 µM) evoked apoptosis. Sertraline (20 and 30 µM) also increased levels of reactive oxygen species. Together, in human osteosarcoma cells, sertraline evoked a [Ca(2+)](i) rise by inducing PLC-dependent Ca(2+) release from the ER and Ca(2+) entry by L-type Ca(2+) channels and store-operated Ca(2+) channels. Sertraline induced cell death that may involve apoptosis by mitochondrial pathways.

Effect of diindolylmethane on Ca2+ homeostasis and viability in PC3 human prostate cancer cells

The effect of the natural product diindolylmethane on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) and viability in PC3 human prostate cancer cells was explored. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)](i). Diindolylmethane at concentrations of 20-50 µM induced [Ca(2+)](i) rise in a concentration-dependent manner. The response was reduced partly by removing Ca(2+). Diindolylmethane-evoked Ca(2+) entry was suppressed by nifedipine, econazole, SK&F96365, protein kinase C modulators and aristolochic acid. In the absence of extracellular Ca(2+), incubation with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) inhibited or abolished diindolylmethane-induced [Ca(2+)](i) rise. Incubation with diindolylmethane also inhibited thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 reduced diindolylmethane-induced [Ca(2+)](i) rise. At concentrations of 50-100 µM, diindolylmethane killed cells in a concentration-dependent manner. This cytotoxic effect was not altered by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Annexin V/PI staining data implicate that diindolylmethane (50 and 100 µM) induced apoptosis in a concentration-dependent manner. In conclusion, diindolylmethane induced a [Ca(2+)](i) rise in PC3 cells by evoking phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via phospholipase A(2)-sensitive store-operated Ca(2+) channels. Diindolylmethane caused cell death in which apoptosis may participate.

Ischemia/Reperfusion injury in liver surgery and transplantation: pathophysiology

Liver ischemia/reperfusion (IR) injury is caused by a heavily toothed network of interactions of cells of the immune system, cytokine production, and reduced microcirculatory blood flow in the liver. These complex networks are further elaborated by multiple intracellular pathways activated by cytokines, chemokines, and danger-associated molecular patterns. Furthermore, intracellular ionic disturbances and especially mitochondrial disorders play an important role leading to apoptosis and necrosis of hepatocytes in IR injury. Overall, enhanced production of reactive oxygen species, found very early in IR injury, plays an important role in liver tissue damage at several points within these complex networks. Many contributors to IR injury are only incompletely understood so far. This paper tempts to give an overview of the different mechanisms involved in the formation of IR injury. Only by further elucidation of these complex mechanisms IR injury can be understood and possible therapeutic strategies can be improved or be developed.

Interfacial stress affects rat alveolar type II cell signaling and gene expression

Previous work from our group (Ravasio A, Hobi N, Bertocchi C, Jesacher A, Dietl P, Haller T. Am J Physiol Cell Physiol 300: C1456-C1465, 2011.) showed that contact of alveolar epithelial type II cells with an air-liquid interface (I(AL)) leads to a paradoxical situation. It is a potential threat that can cause cell injury, but also a Ca(2+)-dependent stimulus for surfactant secretion. Both events can be explained by the impact of interfacial tensile forces on cellular structures. Here, the strength of this mechanical stimulus became also apparent in microarray studies by a rapid and significant change on the transcriptional level. Cells challenged with an I(AL) in two different ways showed activation/inactivation of cellular pathways involved in stress response and defense, and a detailed Pubmatrix search identified genes associated with several lung diseases and injuries. Altogether, they suggest a close relationship of interfacial stress sensation with current models in alveolar micromechanics. Further similarities between I(AL) and cell stretch were found with respect to the underlying signaling events. The source of Ca(2+) was extracellular, and the transmembrane Ca(2+) entry pathway suggests the involvement of a mechanosensitive channel. We conclude that alveolar type II cells, due to their location and morphology, are specific sensors of the I(AL), but largely protected from interfacial stress by surfactant release.

Effect of methoxychlor on Ca(2+) movement and viability in MDCK renal tubular cells

The effect of the insecticide methoxychlor on the physiology of renal tubular cells is unknown. This study aimed to explore the effect of methoxychlor on cytosolic Ca(2+) concentrations ([Ca(2+) ](i) ) in MDCK renal tubular cells using the Ca(2+) -sensitive fluorescent dye fura-2. Methoxychlor at 5-20 μM increased [Ca(2+) ](i) in a concentration-dependent manner. The signal was reduced by 80% by removing extracellular Ca(2+) . Methoxychlor-induced Ca(2+) entry was not affected by nifedipine and SK&F96365 but was inhibited by econazole and protein kinase C modulators. In Ca(2+) -free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) partly inhibited methoxychlor-induced [Ca(2+) ](i) rise. Incubation with methoxychlor also inhibited thapsigargin- or BHQ-induced [Ca(2+) ](i) rise. Inhibition of phospholipase C with U73122 nearly abolished methoxychlor-induced [Ca(2+) ](i) rise. At 5-15 μM, methoxychlor slightly increased cell viability, whereas at 20 μM, it decreased viability. The cytotoxic effect of methoxychlor was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N,N-tetraacetic acid/AM (BAPTA/AM). Annexin V-FITC data suggest that 10 μM methoxychlor inhibited apoptosis, while 20 μM methoxychlor enhanced apoptosis. Methoxychlor (10 and 20 μM) increased the production of reactive oxygen species. Together, in renal tubular cells, methoxychlor induced [Ca(2+) ](i) rise by inducing phospholipase C-dependent Ca(2+) release from multiple stores and Ca(2+) entry via protein kinase C- and econazole-sensitive channels. Methoxychlor slightly enhanced or inhibited cell viability in a concentration-dependent, Ca(2+) -independent manner. Methoxychlor induced cell death that may involve apoptosis via mitochondrial pathways.

Effects and mechanisms of store-operated calcium channel blockade on hepatic ischemia-reperfusion injury in rats

AIM

To further investigate the important role of store-operated calcium channels (SOCs) in rat hepatocytes and to explore the effects of SOC blockers on hepatic ischemia-reperfusion injury (HIRI).

METHODS

Using freshly isolated hepatocytes from a rat model of HIRI (and controls), we measured cytosolic free Ca(2+) concentration (by calcium imaging), net Ca(2+) fluxes (by a non-invasive micro-test technique), the SOC current (I(SOC); by whole-cell patch-clamp recording), and taurocholate secretion [by high-performance liquid chromatography and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays].

RESULTS

Ca(2+) oscillations and net Ca(2+) fluxes mediated by Ca(2+) entry via SOCs were observed in rat hepatocytes. I(SOC) was significantly higher in HIRI groups than in controls (57.0 ± 7.5 pA vs 31.6 ± 2.7 pA, P < 0.05) and was inhibited by La(3+). Taurocholate secretion by hepatocytes into culture supernatant was distinctly lower in HIRI hepatocytes than in controls, an effect reversed by SOC blockers.

CONCLUSION

SOCs are pivotal in HIRI. SOC blockers protected against HIRI and assisted the recovery of secretory function in hepatocytes. Thus, they are likely to become a novel class of effective drugs for prevention or therapy of HIRI patients in the future.

3,3'-Diindolylmethane alters Ca2+ homeostasis and viability in MG63 human osteosarcoma cells

The effect of the natural product 3,3'-diindolylmethane (DIM) on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) and viability in MG63 human osteosarcoma cells was explored. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)](i). DIM at concentrations of 40-80 μM induced a [Ca(2+)](i) rise in a concentration-dependent manner. The response was reduced partly by removing Ca(2+). DIM-evoked Ca(2+) entry was suppressed by nifedipine, econazole, SK&F96365 and protein kinase C modulators. In the absence of extracellular Ca(2+), incubation with the endoplasmic reticulum Ca(2+) pump inhibitors thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) inhibited or abolished DIM-induced [Ca(2+)](i) rise. Incubation with DIM also inhibited thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 abolished DIM-induced [Ca(2+)](i) rise. At concentrations of 10-50 μM, DIM killed cells in a concentration-dependent manner. This cytotoxic effect was not altered by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Annexin V/propidium iodide staining data implicate that DIM (20 and 40 μM) induced apoptosis in a concentration-dependent manner. In sum, in MG63 cells, DIM induced a [Ca(2+)](i) rise by evoking phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via protein kinase C-sensitive store-operated Ca(2+) channels. DIM caused cell death that may involve apoptosis.

Effect of thymol on Ca2+ homeostasis and viability in MG63 human osteosarcoma cells

AIMS

The effect of the natural product thymol on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) and viability in MG63 human osteosarcoma cells was examined.

METHODS

The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)](i).

RESULTS

Thymol at concentrations of 200-1,000 μmol/l induced a [Ca(2+)](i) rise in a concentration-dependent fashion. The response was decreased partially by removal of extracellular Ca(2+). Thymol-induced Ca(2+) entry was inhibited by nifedipine, econazole, SK&F96365 and protein kinase C modulators. When extracellular Ca(2+) was removed, incubation with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) inhibited the thymol-induced [Ca(2+)](i) rise. Incubation with thymol also inhibited the thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 abolished the thymol-induced [Ca(2+)](i) rise. At concentrations of 100-600 μmol/l, thymol killed cells in a concentration-dependent manner. This cytotoxic effect was not changed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/AM. Annexin V/propidium iodide staining data suggest that thymol (200 and 400 μmol/l) induced apoptosis in a concentration-dependent manner. Thymol (200 and 400 μmol/l) also increased levels of reactive oxygen species.

CONCLUSIONS

In MG63 cells, thymol induced a [Ca(2+)](i) rise by inducing phospholipase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via protein kinase C-sensitive store-operated Ca(2+) channels. Thymol induced cell death that may involve apoptosis via mitochondrial pathways.

Effect of thymol on Ca2+ homeostasis and viability in human glioblastoma cells

The effect of the natural essential oil thymol on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) and viability in human glioblastoma cells was examined. The Ca(2+)-sensitive fluorescent dye fura-2 was applied to measure [Ca(2+)](i). Thymol at concentrations of 400-1000 μM induced a [Ca(2+)](i) rise in a concentration-dependent fashion. The response was decreased partially by removal of extracellular Ca(2+). Thymol-induced Ca(2+) signal was not altered by nifedipine, econazole, SK&F96365, and protein kinase C activator phorbol myristate acetate (PMA), but was inhibited by the protein kinase C inhibitor GF109203X. When extracellular Ca(2+) was removed, incubation with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) abolished thymol-induced [Ca(2+)](i) rise. Incubation with thymol also abolished thapsigargin or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 abolished thymol-induced [Ca(2+)](i) rise. At concentrations of 200-800 μM, thymol killed cells in a concentration-dependent manner. This cytotoxic effect was not changed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/acetoxy methyl (BAPTA/AM). Annexin V/propidium iodide staining data suggest that thymol (200, 400 and 600 μM) induced apoptosis in a concentration-dependent manner. Collectively, in human glioblastoma cells, thymol induced a [Ca(2+)](i) rise by inducing phospholipase C- and protein kinase C-dependent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via non store-operated Ca(2+) channels. Thymol induced cell death that may involve apoptosis.

Mitochondrial pathway mediates the antileukemic effects of Hemidesmus indicus, a promising botanical drug

Background

Although cancers are characterized by the deregulation of multiple signalling pathways, most current anticancer therapies involve the modulation of a single target. Because of the enormous biological diversity of cancer, strategic combination of agents targeted against the most critical of those alterations is needed. Due to their complex nature, plant products interact with numerous targets and influence several biochemical and molecular cascades. The interest in further development of botanical drugs has been increasing steadily and the FDA recently approved the first new botanical prescription drug. The present study is designed to explore the potential antileukemic properties of Hemidesmus indicus with a view to contributing to further development of botanical drugs. Hemidesmus was submitted to an extensive in vitro preclinical evaluation.

Methodology/Principal Findings

A variety of cellular assays and flow cytometry, as well as a phytochemical screening, were performed on different leukemic cell lines. We have demonstrated that Hemidesmus modulated many components of intracellular signaling pathways involved in cell viability and proliferation and altered the protein expression, eventually leading to tumor cell death, mediated by a loss of mitochondrial transmembrane potential and increased Bax/Bcl-2 ratio. ADP, adenine nucleotide translocator and mitochondrial permeability transition pore inhibitors did not reverse Hemidesmus-induced mitochondrial depolarization. Hemidesmus induced a significant [Ca²⁺]_i raise through the mobilization of intracellular Ca²⁺ stores. Moreover, Hemidesmus significantly enhanced the antitumor activity of three commonly used chemotherapeutic drugs (methotrexate, 6-thioguanine, cytarabine). A clinically relevant observation is that its cytotoxic activity was also recorded in primary cells from acute myeloid leukemic patients.

Conclusions/Significance

These results indicate the molecular basis of the antileukemic effects of Hemidesmus and identify the mitochondrial pathways and [Ca²⁺]_i as crucial actors in its anticancer activity. On these bases, we conclude that Hemidesmus can represent a valuable tool in the anticancer pharmacology, and should be considered for further investigations.