Membrane stretch and cytoplasmic Ca2+ independently modulate stretch-activated BK channel activity

Large conductance Ca²⁺-activated K⁺ (BK) channels are responsible for changes in chemical and physical signals such as Ca²⁺, Mg²⁺ and membrane potentials. Previously, we reported that a BK channel cloned from chick heart (SAKCaC) is activated by membrane stretch. Molecular cloning and subsequent functional characterization of SAKCaC have shown that both the membrane stretch and intracellular Ca²⁺ signal allosterically regulate the channel activity via the linker of the gating ring complex. Here we investigate how these two gating principles interact with each other. We found that stretch force activated SAKCaC in the absence of cytoplasmic Ca²⁺. Lack of Ca²⁺ bowl (a calcium binding motif) in SAKCaC diminished the Ca²⁺-dependent activation, but the mechanosensitivity of channel was intact. We also found that the abrogation of STREX (a proposed mechanosensing apparatus) in SAKCaC abolished the mechanosensitivity without altering the Ca²⁺ sensitivity of channels. These observations indicate that membrane stretch and intracellular Ca²⁺ could independently modulate SAKCaC activity.     

Hypoxia increases BK channel activity in the inner mitochondrial membrane

To explore the potential function of the BK channel in the inner mitochondrial membrane under physiological and hypoxic conditions, we used on-mitoplast and whole-mitoplast patches. Single BK channels had a conductance of 276+/-9 pS under symmetrical K(+) solutions, were Ca(2+)- and voltage-dependent and were inhibited by 0.1 microM charybdotoxin. In response to hypoxia, BK increased open probability, shifted its reversal potential (9.3+/-2.4 mV) in the positive direction and did not change its conductance. We conclude that (1) the properties at rest of this mitoplast K(+) channel are similar to those of BK channels in the plasma membrane; (2) hypoxia induces an increase, rather than a decrease (as in the plasmalemma), in the open probability of this K(+) channel, leading to K(+) efflux from the mitochondrial matrix to the outside. We speculate that this increase in K(+) efflux from mitochondria into the cytosol is important during hypoxia in maintaining cytosolic K(+).     

Evaluation of a role for intracellular Na+, K+, Ca2+, and Mg2+ in hyperthermic cell killing

A dose of heat which renders 98% of a population of Chinese hamster ovary cells reproductively dead has no significant effect on their Na+, K+, or Mg2+ content by 28 h postheat. In contrast, the cellular Ca2+ content increases in a dose-dependent manner as observed at 22 h after heating for 15-35 min at 45 degrees C. However, the rates of both influx and efflux of Ca2+ were reduced by heating. Increasing the cellular Ca2+ content by incubating the cells in high extracellular Ca2+, either at the time of heating or for a period of 22 h following heat, does not potentiate the lethal effect of heat. Completely blocking the heat-induced increase in Ca2+ content by incubating the cells in medium containing a low Ca2+ concentration does not protect the cells. Therefore, we conclude that heat does not produce any significant changes in the Na+, K+, or Mg2+ content of cells and that the heat-induced increase in Ca2+ does not play an important role in hyperthermic cell killing.     

Modulation of acid-sensing ion channel currents, acid-induced increase of intracellular Ca2+, and acidosis-mediated neuronal injury by intracellular pH

Acid-sensing ion channels (ASICs), activated by lowering extracellular pH (pH(o)), play an important role in normal synaptic transmission in brain and in the pathology of brain ischemia. Like pH(o), intracellular pH (pH(i)) changes dramatically in both physiological and pathological conditions. Although it is known that a drop in pH(o) activates the ASICs, it is not clear whether alterations of pH(i) have an effect on these channels. Here we demonstrate that the overall activities of ASICs, including channel activation, inactivation, and recovery from desensitization, are tightly regulated by pH(i). In cultured mouse cortical neurons, bath perfusion of the intracellular alkalizing agent quinine increased the amplitude of the ASIC current by approximately 50%. In contrast, intracellular acidification by withdrawal of NH(4)Cl or perfusion of propionate inhibited the current. Increasing pH buffering capacity in the pipette solution with 40 mm HEPES attenuated the effects of quinine and NH(4)Cl. The effects of intracellular alkalizing/acidifying agents were mimicked by using intracellular solutions with pH directly buffered at high/low values. Increasing pH(i) induced a shift in H(+) dose-response curve toward less acidic pH but a shift in the steady state inactivation curve toward more acidic pH. In addition, alkalizing pH(i) induced an increase in the recovery rate of ASICs from desensitization. Consistent with its effect on the ASIC current, changing pH(i) has a significant influence on the acid-induced increase of intracellular Ca(2+), membrane depolarization, and acidosis-mediated neuronal injury. Our findings suggest that changes in pH(i) may play an important role in determining the overall function of ASICs in both physiological and pathological conditions.     

Tributyltin increases cytosolic free Ca2+ concentration in thymocytes by mobilizing intracellular Ca2+, activating a Ca2+ entry pathway, and inhibiting Ca2+ efflux.

The immunotoxic environmental pollutant tri-n-butyltin (TBT) kills thymocytes by apoptosis through a mechanism that requires an increase in intracellular Ca2+ concentration. The addition of TBT (EC50 = 2 microM) to fura-2-loaded rat thymocytes resulted in a rapid and sustained increase in the cytosolic free Ca2+ concentration ([Ca2+]i) to greater than 1 microM. In nominally Ca(2+)-free medium, TBT slightly but consistently increased thymocyte [Ca2+]i by about 0.11 microM. The subsequent restoration of CaCl2 to the medium resulted in a sustained overshoot in [Ca2+]i; similarly, the addition of MnCl2 produced a rapid decrease in the intracellular fura-2 fluorescence in thymocytes exposed to TBT. The rates of Ca2+ and Mn2+ entry stimulated by TBT were essentially identical to the rates stimulated by 2,5-di-(tert.-butyl)-1,4-benzohydroquinone (tBuBHQ), which has previously been shown to empty the agonist-sensitive endoplasmic reticular Ca2+ store and to stimulate subsequent Ca2+ influx by a capacitative mechanism. The addition of excess [ethylenebis(oxyethylenenitrilo)]tetraacetic acid to thymocytes produced a rapid return to basal [Ca2+]i after tBuBHQ treatment but a similar rapid return to basal [Ca2+]i was not observed after TBT treatment. In addition, TBT produced a marked inhibition of both Ca2+ efflux from the cells and the plasma membrane Ca(2+)-ATPase activity. Also, TBT treatment resulted in a rapid decrease in thymocyte ATP level. Taken together, our results show that TBT increases [Ca2+]i in thymocytes by the combination of intracellular Ca2+ mobilization, stimulation of Ca2+ entry, and inhibition of the Ca2+ efflux process. Furthermore, the ability of TBT to apparently mobilize the tBuBHQ-sensitive intracellular Ca2+ store followed by Ca2+ and Mn2+ entry suggests that the TBT-induced [Ca2+]i increase involves a capacitative type of Ca2+ entry.     

Relaxing effects of 5-oxo-ETE on human bronchi involve BK Ca channel activation

The present study investigated the ability of 5-oxo-EicosaTetraEnoic acid (5-oxo-ETE) for modulating airway smooth muscle (ASM) tone in human bronchi. 5-Oxo-ETE induced a concentration-dependent relaxing effect on human bronchi pre-contracted with methacholine (MCh) and arachidonic acid (AA). This relaxing response was highly sensitive to Iberiotoxin (IbTx), a large conducting Ca(2+)-activated K(+) channel (BK(Ca)) inhibitor. Furthermore, microelectrode measurements revealed that 5-oxo-ETE (0.1-10 microM) hyperpolarizes the membrane potential of human bronchial ASM cells. These hyperpolarizing effects were also inhibited in the presence of 10nM IbTx. Lastly, 5-oxo-ETE was shown to directly activate reconstituted BK(Ca) channels derived from human airway smooth muscles. In summary, the 5-oxo-ETE eicosanoid activates a specific K(+) conductance, involved in membrane hyperpolarization, which in turn reduces Ca(2+) entry and facilitates relaxation of smooth muscle cells.     

Effect of calmodulin on myometrial cell membrane Ca2+,Mg2+-ATPase activity

Myometrium cell plasma membrane Ca2+, Mg(2+)-ATPase purified by an affinity chromatography on calmodulin-sepharose 4B is calmodulin-dependent enzyme. Concentration of calmodulin required for half-maximal activation of enzyme was about 26 nM. By unlike to the enzymes originated from other tissues sensitivity to the calmodulin of the myometrial sarcolemma Ca(2+)-transporting ATPase was lower: calmodulin increased Vmax of ATPase about 1.25-fold, the apparent constant of the activation of enzyme by Ca2+ failed to alter independently on the phospholipid presenting at the enzyme isolation.     

Calcitriol increases Ca2+-ATPase activity

Treatment with calcitriol of isolated cartilage cells derived from epiphyseal growth plates of rachitic chicks results in reduced intracellular calcium concentrations. The reduction in calcium was found to correlate with increased activity of Ca2+-ATPase. The activities of Na+-K+-ATPase and of Mg2+-ATPase did not change in response to the treatment with calcitriol. It is suggested that calcitriol regulates intracellular calcium by modulating the activity of the Ca2+-pumping ATPase.     

Ophiobolin A induces paraptosis-like cell death in human glioblastoma cells by decreasing BKCa channel activity

Glioblastoma multiforme (GBM) is the most lethal and common malignant human brain tumor. The intrinsic resistance of highly invasive GBM cells to radiation- and chemotherapy-induced apoptosis accounts for the generally dismal treatment outcomes. This study investigated ophiobolin A (OP-A), a fungal metabolite from Bipolaris species, for its promising anticancer activity against human GBM cells exhibiting varying degrees of resistance to proapoptotic stimuli. We found that OP-A induced marked changes in the dynamic organization of the F-actin cytoskeleton, and inhibited the proliferation and migration of GBM cells, likely by inhibiting big conductance Ca²⁺-activated K⁺ channel (BKCa) channel activity. Moreover, our results indicated that OP-A induced paraptosis-like cell death in GBM cells, which correlated with the vacuolization, possibly brought about by the swelling and fusion of mitochondria and/or the endoplasmic reticulum (ER). In addition, the OP-A-induced cell death did not involve the activation of caspases. We also showed that the expression of BKCa channels colocalized with these two organelles (mitochondria and ER) was affected in this programmed cell death pathway. Thus, this study reveals a novel mechanism of action associated with the anticancer effects of OP-A, which involves the induction of paraptosis through the disruption of internal potassium ion homeostasis. Our findings offer a promising therapeutic strategy to overcome the intrinsic resistance of GBM cells to proapoptotic stimuli.     

Inositol hexakisphosphate increases L-type Ca2+ channel activity by stimulation of adenylyl cyclase.

Inositol hexakisphosphate (InsP6) is a most abundant inositol polyphosphate that changes simultaneously with inositol 1,4,5-trisphosphate in depolarized neurons. However, the role of InsP6 in neuronal signaling is unknown. Mass assay reveals that the basal levels of InsP6 in several brain regions tested are similar. InsP6 mass is significantly elevated in activated brain neurons and lowered by inhibition of neuronal activity. Furthermore, the hippocampus is most sensitive to electrical challenge with regard to percentage accumulation of InsP6. In hippocampal neurons, InsP6 stimulates adenylyl cyclase (AC) without influencing cAMP phosphodiesterases, resulting in activation of protein kinase A (PKA) and thereby selective enhancement of voltage-gated L-type Ca2+ channel activity. This enhancement was abolished by preincubation with PKA and AC inhibitors. These data suggest that InsP6 increases L-type Ca2+ channel activity by facilitating phosphorylation of PKA phosphorylation sites. Thus, in hippocampal neurons, InsP6 serves as an important signal in modulation of voltage-gated L-type Ca2+ channel activity.     

Blockage of Ca(2+)-permeable AMPA receptors suppresses migration and induces apoptosis in human glioblastoma cells

Glioblastoma multiforme is the most undifferentiated type of brain tumor, and its prognosis is extremely poor. Glioblastoma cells exhibit highly migratory and invasive behavior, which makes surgical intervention unsuccessful. Here, we showed that glioblastoma cells express Ca(2+)-permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-type glutamate receptors assembled from the GluR1 and/or GluR4 subunits, and that their conversion to Ca(2+)-impermeable receptors by adenovirus-mediated transfer of the GluR2 cDNA inhibited cell locomotion and induced apoptosis. In contrast, overexpression of Ca(2+)-permeable AMPA receptors facilitated migration and proliferation of the tumor cells. These findings indicate that Ca(2+)-permeable AMPA receptors have crucial roles in growth of glioblastoma. Blockage of these Ca(2+)-permeable receptors may be a useful therapeutic strategy for the prevention of glioblastoma invasion.     

HGF/SF and menthol increase human glioblastoma cell calcium and migration

This study explored the role of transient receptor potential melastatin 8 ion channels (TRPM8) in mechanisms of human glioblastoma (DBTRG) cell migration. Menthol stimulated influx of Ca²⁺, membrane current, and migration of DBTRG cells. Effects on Ca²⁺ and migration were enhanced by pre-treatment with hepatocyte growth factor/scatter factor (HGF/SF). Effects on Ca²⁺ also were greater in migrating cells compared with non-migrating cells. 2-Aminoethoxydiphenyl borate (2-APB) inhibited all menthol stimulations. RT-PCR and immunoblot analysis showed that DBTRG cells expressed both mRNA and protein for TRPM8 ion channels. Two proteins were evident: one (130-140 kDa) in a plasma membrane-enriched fraction, and a variant (95-100 kDa) in microsome- and plasma membrane-enriched fractions. Thus, TRPM8 plays a role in mechanisms that increase [Ca²⁺]_i needed for DBTRG cell migration.     

Hepcidin increases intracellular Ca2+ of osteoblast hFOB1.19 through L-type Ca2+ channels

Hepcidin is a key player in the regulation of iron homeostasis. Several pathological conditions associated with iron overload are attributed to the depressed expression of hepcidin and are often associated with bone diseases including osteoporosis. Hepcidin was suggested to have anti-osteoporosis effects by preventing iron overload. We recently observed that hepcidin could increase intracellular calcium concentration in cultured osteoblast cells. The present study was designed to elucidate the source of the increased intracellular calcium following hepcidin activation. Cultured hFOB1.19 cells were used to test whether there was a dose dependent effect of hepcidin on increasing intracellular calcium. After finding the optimal concentration in increasing intracellular calcium, Cultured hFOB1.19 cells were then divided into three groups: (1) control group, (2) and (3) groups pretreated with either nimodipine (2 × 10(-5)mol/L) or EDTA (2 × 10(-3)mol/L) for 10 min before incubation with hepcidin (100 nmol/L). All cells were stimulated with hepcidin for 60 min and then stained with fluo-3/AM for 40 min before the intracellular calcium was observed using flow cytometry (FCM). As compared with controls, hepcidin treatment significantly increased intracellular calcium concentration. This effect was blocked by nimodipine and EDTA pretreatments which suggested that hepcidin-mediated calcium inflow was mainly through L-type Ca(2+) channels and that the release of intracellular calcium store was not significant. Hepcidin increases of intracellular calcium may be related to its anti-osteoporosis effect but this hypothesis needs further investigation.     

The NH2 terminus of RCK1 domain regulates Ca2+-dependent BK(Ca) channel gating

Large conductance, voltage- and Ca2+-activated K+ (BK(Ca)) channels regulate blood vessel tone, synaptic transmission, and hearing owing to dual activation by membrane depolarization and intracellular Ca2+. Similar to an archeon Ca2+-activated K+ channel, MthK, each of four alpha subunits of BK(Ca) may contain two cytosolic RCK domains and eight of which may form a gating ring. The structure of the MthK channel suggests that the RCK domains reorient with one another upon Ca2+ binding to change the gating ring conformation and open the activation gate. Here we report that the conformational changes of the NH2 terminus of RCK1 (AC region) modulate BK(Ca) gating. Such modulation depends on Ca2+ occupancy and activation states, but is not directly related to the Ca2+ binding sites. These results demonstrate that AC region is important in the allosteric coupling between Ca2+ binding and channel opening. Thus, the conformational changes of the AC region within each RCK domain is likely to be an important step in addition to the reorientation of RCK domains leading to the opening of the BK(Ca) activation gate. Our observations are consistent with a mechanism for Ca2+-dependent activation of BK(Ca) channels such that the AC region inhibits channel activation when the channel is at the closed state in the absence of Ca2+; Ca2+ binding and depolarization relieve this inhibition.     

八肽胆囊收缩素激活钙离子通道和酪氨酸激酶诱导豚鼠心肌细胞内的游离钙增高

探讨八肽胆囊收缩素(CCK-8)对豚鼠单个心肌细胞内游离钙浓度([Ca2+]i的影响及其信号转导机制.Fluo3-AM标记酶消化法分离的单个心室肌细胞,用激光共聚焦显微镜测定细胞内[Ca2+]i的浓度.[Ca2+]i的变化用荧光强度(Fi)和相对荧光强度(Fi/F0%)表示.实验结果如下(1)在含Ca2+1.0mmol/L的Tyrode's液中,CCK-8(1～104pmoVL)均可引起[Ca2+]i快速显著上升(P＜0.01).(2)用钙离子鳌合剂EGTA(3mmol/L)和钙离子通道阻断剂nisoldipine(0.5μmol/L)预孵育心肌细胞5min,CCK-8(102pmol/L)仅可引起[Ca2+]i缓慢轻度上升(P＜0.01).(3)用非选择性CCK受体拮抗剂丙谷胺(proglumide6μmo1/L)或酪氨酸激酶抑制剂genistein(1 μmol/L)预孵育心肌细胞5 min,则完全抑制CCK-8诱导的[Ca2+]i升高(P＜0.01).CCK-8可通过激活其受体控制的Ca2+通道,引起Ca2+内流,诱导细胞内Ca2+释放,引起豚鼠单个心肌细胞内[Ca2+]i上升,此作用可能由酪氨酸激酶介导.     

Metal-driven operation of the human large-conductance voltage- and Ca2+-dependent potassium channel (BK) gating ring apparatus

Large-conductance voltage- and Ca(2+)-dependent K(+) (BK, also known as MaxiK) channels are homo-tetrameric proteins with a broad expression pattern that potently regulate cellular excitability and Ca(2+) homeostasis. Their activation results from the complex synergy between the transmembrane voltage sensors and a large (>300 kDa) C-terminal, cytoplasmic complex (the "gating ring"), which confers sensitivity to intracellular Ca(2+) and other ligands. However, the molecular and biophysical operation of the gating ring remains unclear. We have used spectroscopic and particle-scale optical approaches to probe the metal-sensing properties of the human BK gating ring under physiologically relevant conditions. This functional molecular sensor undergoes Ca(2+)- and Mg(2+)-dependent conformational changes at physiologically relevant concentrations, detected by time-resolved and steady-state fluorescence spectroscopy. The lack of detectable Ba(2+)-evoked structural changes defined the metal selectivity of the gating ring. Neutralization of a high-affinity Ca(2+)-binding site (the "calcium bowl") reduced the Ca(2+) and abolished the Mg(2+) dependence of structural rearrangements. In congruence with electrophysiological investigations, these findings provide biochemical evidence that the gating ring possesses an additional high-affinity Ca(2+)-binding site and that Mg(2+) can bind to the calcium bowl with less affinity than Ca(2+). Dynamic light scattering analysis revealed a reversible Ca(2+)-dependent decrease of the hydrodynamic radius of the gating ring, consistent with a more compact overall shape. These structural changes, resolved under physiologically relevant conditions, likely represent the molecular transitions that initiate the ligand-induced activation of the human BK channel.     

External bioenergy-induced increases in intracellular free calcium concentrations are mediated by Na+/Ca2+ exchanger and L-type calcium channel

External bioenergy (EBE, energy emitted from a human body) has been shown to increase intracellular calcium concentration ([Ca²⁺]_i, an important factor in signal transduction) and regulate the cellular response to heat stress in cultured human lymphoid Jurkat T cells. In this study, we wanted to elucidate the underlying mechanisms. A bioenergy specialist emitted bioenergy sequentially toward tubes of cultured Jurkat T cells for one 15-minute period in buffers containing different ion compositions or different concentrations of inhibitors. [Ca²⁺]_i was measured spectrofluorometrically using the fluorescent probe fura-2. The resting [Ca²⁺]_i in Jurkat T cells was 70 ± 3 nM (n = 130) in the normal buffer. Removal of external calcium decreased the resting [Ca²⁺]_i to 52 ± 2 nM (n = 23), indicating that [Ca²⁺] entry from the external source is important for maintaining the basal level of [Ca²⁺]_i. Treatment of Jurkat T cells with EBE for 15 min increased [Ca²⁺]_i by 30 ± 5% (P 0.05, Student t-test). The distance between the bioenergy specialist and Jurkat T cells and repetitive treatments of EBE did not attenuate [Ca²⁺]_i responsiveness to EBE. Removal of external Ca²⁺ or Na⁺, but not Mg²⁺, inhibited the EBE-induced increase in [Ca²⁺]_i. Dichlorobenzamil, an inhibitor of Na⁺/Ca²⁺ exchangers, also inhibited the EBE-induced increase in [Ca²⁺]_i in a concentration-dependent manner with an IC50 of 0.11 ± 0.02 nM. When external [K⁺] was increased from 4.5 mM to 25 mM, EBE decreased [Ca²⁺]_i. The EBE-induced increase was also blocked by verapamil, an L-type voltage-gated Ca²⁺ channel blocker. These results suggest that the EBE-induced [Ca²⁺]_i increase may serve as an objective means for assessing and validating bioenergy effects and those specialists claiming bioenergy capability. The increase in [Ca²⁺]_i is mediated by activation of Na⁺/Ca²⁺ exchangers and opening of L-type voltage-gated Ca²⁺ channels. (Mol Cell Biochem 271: 51–59, 2005)     

Menthol blocks dihydropyridine-insensitive Ca2+ channels and induces neurite outgrowth in human neuroblastoma cells

Voltage-gated Ca2+ channels were identified in LA-N-5 human neuroblastoma cells using the Ca2+ sensitive fluorescent probe, fura-2. Using a variety of "classical" Ca2+ channel blockers, we have demonstrated the presence of both dihydropyridine (DHP)-sensitive and -insensitive channel types that can be activated by depolarization of the cells with either high K+ or gramicidin in the bathing solution. Brief exposure of LA-N-5 cells to menthol blunted the depolarization-induced Ca2+ influx though both DHP-sensitive and DHP-insensitive channels. This effect is concentration dependent (50% maximal blocking effect with 0.25 mM menthol), rapid in onset, and readily reversible. The specificity of the Ca2(+)-channel blocking effect of menthol was demonstrated in parallel studies using compounds with similar structures: menthone blocked Ca2+ channels with about half the potency of menthol, while cyclohexanol was without effect. Addition of either menthol or menthone to LA-N-5 cultures induced neurite outgrowth, cellular clustering, and reduction of cell growth in a dose-dependent fashion that correlated with the ability of these compounds to inhibit the DHP-insensitive Ca2+ influx. Cyclohexanol had no biologic activity. Taken together, the parallel potency for blockade of DHP-insensitive Ca2+ influx with the biologic activity of menthol suggests a role for certain types of Ca2+ channels in triggering growth and morphologic changes in LA-N-5 cells.     

Activation of human alveolar macrophages via P2 receptors: coupling to intracellular Ca2+ increases and cytokine secretion

Alveolar macrophages play a crucial role in the pathogenesis of inflammatory airway diseases. By the generation and release of different inflammatory mediators they contribute to both recruitment of different leukocytes into the lung and to airway remodeling. A potent stimulus for the release of inflammatory cytokines is ATP, which mediates its cellular effects through the interaction with different membrane receptors, belonging to the P2X and P2Y families. The aim of this study was to characterize the biological properties of purinoceptors in human alveolar macrophages obtained from bronchoalveolar lavages in the context of inflammatory airway diseases. The present study is the first showing that human alveolar macrophages express mRNA for different P2 subtypes, namely P2X(1), P2X(4), P2X(5), P2X(7), P2Y(1), P2Y(2), P2Y(4), P2Y(6), P2Y(11), P2Y(13), and P2Y(14). We also showed that extracellular ATP induced Ca(2+) transients and increased IL-1beta secretion via P2X receptors. Furthermore, extracellular nucleotides inhibited production of IL-12p40 and TNF-alpha, whereas IL-6 secretion was up-regulated. In summary, our data further support the hypothesis that purinoceptors are involved in the pathogenesis of inflammatory lung diseases.     

Hydrogen peroxide enhanced Ca(2+)-activated BK currents and promoted cell injury in human dermal fibroblasts

AimsRecent studies have shown that dermal fibroblasts possess multiple types of voltage-dependent K⁺ channels, and the activation of these channels induces apoptosis. In the present study, we aimed to investigate whether hydrogen peroxide (H₂O₂), an oxidative stress inducer, could modulate these channels or induce human dermal fibroblasts injury.Main methodsThe effects of H₂O₂ on K⁺ currents were studied using a whole-cell recording. Intracellular PKC levels were measured with a direct human PKC enzyme immunoassay kit. Cell viability was assessed using PI staining and apoptotic nuclei were detected with TdT-mediated digoxigenin-dUTP nick-end labelling assay (TUNEL) assay.Key findingsTreatment of cells with 100 μM H₂O₂ resulted in a partially reversible increase in non-inactivating outward K⁺ currents and an alteration in the steady-state activation property of the channels. The H₂O₂-induced increase in K⁺ currents was mimicked by a PKC activator, and was blocked by the PKC inhibitor or the large conductance Ca²⁺-activited K⁺ (BK) channel blockers. The intracellular PKC levels were significantly enhanced by H₂O₂ treatment in a concentration-dependent manner. After exposure to H₂O₂, evaluation of fibroblasts survival rate and damaged cell number with TUNEL-positive nuclei revealed an increased cell injury. Blocking the K⁺ channels with blockers significantly decreased the H₂O₂-induced human dermal fibroblasts injury.SignificanceOur results revealed that H₂O₂ could enhance BK currents by PKC pathway. Increased K⁺ currents might be related to H₂O₂-induced human dermal fibroblasts injury. The results reported here contribute to our understanding of the mechanism underlying H₂O₂-induced human dermal fibroblasts injury.