TRPC1 is involved in Ca2+ influx and cytotoxicity following Pb2+ exposure in human embryonic kidney cells

Lead inhibits microglial cell migration via suppression of store-operated calcium entry

Lead (Pb) is a non-biodegradable environmental pollutant that can lead to neurotoxicity by inducing neuroinflammation. Microglial activation plays a key role in neuroinflammation, and microglial migration is one of its main features. However, whether Pb affects microglial migration has not yet been elucidated. Herein, the effect of Pb on microglial migration was investigated using BV-2 microglial cells and primary microglial cells. The results showed that cell activation markers (TNF-α and CD206) in BV-2 cells were increased after Pb treatment. The migration ability of microglia was inhibited by Pb. Both store-operated calcium entry (SOCE) and the Ca2+ release-activated Ca2+ (CRAC) current were downregulated by microglia treatment with Pb in a dose-dependent manner. However, there was no statistical difference in the protein levels of stromal interaction molecule (STIM) 1, STIM2, or Ca2+ release-activated Ca2+ channel protein (Orai) 1 in microglia. The external Ca2+ influx and cell migration ability were restored to a certain extent after overexpression of either STIM1 or its CRAC activation domain in microglia. These results indicated that Pb inhibits microglial migration by downregulation of SOCE and impairment of the function of STIM1.

Potential mechanism of lead poisoning to the growth and development of ovarian follicle

With the rapid development of economic globalization and industrialization, lead (Pb), one of the most important heavy metals, has been used widely since antiquity for several purposes. In fact, its impact on the health of animals and humans is a significant public health risk all the time. Pb could be accumulated in the body for a long time, causing irreversible damage to the health of animals and humans, including hostile reproductive health. Up to now, although there are some published studies on impeding the normal development of ovarian folliculogenesis of female resulted from Pb exposure, with the damage of structure in uterine tissue, the imbalance of female menstrual status, and the change of hormone levels. The potential mechanism of Pb exposure on female reproduction system, however, remains enigmatic. How to alleviate the damage of Pb toxicity to reproductive function of female has become an urgent problem. Therefore, the aim of the present review is to discuss the information on the growth and development of ovarian follicle of mammalians and the potential toxic mechanism when exposed to Pb. The literatures were collected via various websites and consulting books, reports, etc. In summary, Pb impair folliculogenesis of mammalians, which may be related to the interference to the hypothalamic-pituitary-gonadal (HPG) axis and the production of reactive oxygen species (ROS), in turn impairs various molecules including proteins, lipids and DNA, as well as the disruption of the antioxidant defense system, ionic equilibrium and endoplasmic reticulum homeostasis.

Bioimaging of Pb and STIM1 in mice liver, kidney and brain using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and immunohistochemistry

Lead (Pb) pollution is one of the most serious environmental problems and has attracted worldwide attention. Pb causes hematological, central nervous system, as well as renal toxicity, and so on. Although many investigations about Pb in blood to evaluate pollution status and toxic effects have been reported, there are open question about biological behavior of Pb. In order to reveal any toxicological mechanisms or influences, we focused on the local distribution of Pb in mice organs. Lead acetate (100 mg/L and 1000 mg/L) in drinking water were given to the BALB/c mice (male, seven weeks of age, N = 24) for three weeks. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis revealed a homogenous distribution of Pb in the liver and inhomogeneous distribution in the kidney and brain. The hippocampus, thalamus, and hypothalamus had higher concentrations than other areas such as the white matter. Surprisingly, in the kidney, Pb tended to accumulate in the medulla rather than the cortex, strongly suggesting that high sensitivity areas and high accumulation areas differ. Moreover, distribution of stromal interacting protein 1 (STIM1) which is candidate gene of Pb pathway to the cells was homogenous in the liver and kidney whereas inhomogeneous in the brain. In contrast to our hypothesis, interestingly, Pb exposure under the current condition did not induce mRNA expressions for any candidate channel or transporter genes. Thus, further study should be conducted to elucidate the local distribution of Pb and other toxic metals, and pathway that Pb takes to the cells.

Effects of secondary biological treatment plant effluent administration, as drinking water, to rats' urogenital system in relation to cadmium and lead accumulation

The aim of this study was to examine the effect of the secondary biological treatment plant effluent administration on the kidneys, urinary bladder, and testis of Wistar rats in relation to lead (Pb) and cadmium (Cd) accumulation, since such an effluent is used for irrigation of edible plants. Male Wistar rats, randomly assigned into 5 groups, were treated with domestic sewage effluent (DSE) for 24 months. Cadmium and lead concentrations in the DSE, rats' tissues, and urine were estimated by means of atomic spectroscopy. Lead was rapidly accumulated in high amounts in rats' kidney and to a lesser extent in the testis whereas Cd concentration was raised in all tissues examined. Deposition of Cd and Pd in the kidney of the rats resulted in profound damage over time. The results showed that long-term administration to DSE as drinking water exposes living organisms to urogenital stress related to heavy metal concentration and pH of the effluent.

Protective effect of Vitamin D3 against lead induced hepatotoxicity, oxidative stress, immunosuppressive and calcium homeostasis disorders in rat

Lead (Pb) is an extremely poisonous, non-essential trace element and toxicity develops in humans following frequent exposure to the heavy metal in polluted environmental and occupational settings. Pb induces hepatic damage through the depletion of the antioxidant system, enhancing cellular oxidative stress and stimulation of proinflammatory cytokines. Although the antioxidant and anti-inflammatory actions of vitamin D₃ (VD₃) are well-established, a minority of studies measured the protective actions of VD₃ against Pb toxicity. Therefore, this work studied the effects of vitamin VD₃ therapy on the fundamental molecular basis underlying hepatic injury induced by chronic Pb toxicity. Twenty-four adult male rats were distributed equally into the negative controls (NC), positive controls (PC) and VD3 groups. While both the PC and VD3 groups received Pb-acetate in drinking water (1000 mg/L) for four weeks, the latter group also received intramuscular VD3 injections (1000 IU/kg; 3 days/week) simultaneously with Pb. The liver enzymes together with the serum and hepatic tissue Pb concentrations increased markedly in the PC group compared with the NC group. Pb toxicity also drastically induced hepatocyte apoptosis/necrosis, increased the hepatic tissue concentrations of malondialdehyde and the pro-inflammatory cytokines (TGF-β, IL-4 & TNF-α) as well as reduced the anti-oxidative enzymes (GSH, GPx & CAT) and the anti-inflammatory cytokine, IL-10, compared with the NC group. Pb also significantly decreased the serum concentrations of VD3 and Ca²⁺. Additionally, the hepatic expressions of VD receptor, Cyp24a1 enzyme, L-type Ca²⁺-channel, calbindin-D_28k & -D_29k, calmodulin and calmodulin-dependent protein kinase II were significantly upregulated, whereas the VD binding protein, CYP2R1 enzyme and T-type Ca²⁺-channel were markedly inhibited at the gene and protein levels following Pb intoxication. VD3 alleviated the hepatic damage, inhibited the oxidative stress and pro-inflammatory molecules as well as upregulated the anti-oxidant and anti-inflammatory markers and restored the expression of the VD/Ca²+ regulatory molecules compared with the PC group. VD3 supplementation discloses promising protective effects against Pb-induced hepatic damage, through its anti-inflammatory and antioxidant actions as well as by modulating the hepatocyte calcium homeostatic molecules.

Activation of TRPC6 channels contributes to (+)-conocarpan-induced apoptotic cell death in HK-2 cells

(+)-Conocarpan (CNCP), a neolignan frequently found in many medicinal and edible plants displays a broad spectrum of bioactivity. Here, we demonstrated that CNCP induced apoptotic cell death in human kidney-2 (HK-2) cells in a concentration-dependent manner (IC₅₀ = 19.3 μM) and led to the sustained elevation of intracellular Ca²⁺ ([Ca²⁺]_i). Lower extracellular Ca²⁺ concentrations from 2.3 mM to 0 mM significantly suppressed the CNCP-induced Ca²⁺ response by 69.1%. Moreover, the depletion of intracellular Ca²⁺ stores using thapsigargin normalized CNCP-induced Ca²⁺ release from intracellular Ca²⁺ stores, suggesting that the CNCP-induced Ca²⁺ response involved both extracellular Ca²⁺ influx and Ca²⁺ release from intracellular Ca²⁺ stores. SAR7334, a TRPC3/6/7 channel inhibitor, but neither Pyr3, a selective TRPC3 channel inhibitor, nor Pico145, a TRPC1/4/5 inhibitor, suppressed the CNCP-induced Ca²⁺ response by 57.2% and decreased CNCP-induced cell death by 53.4%, suggesting a critical role for TRPC6 channels in CNCP-induced Ca²⁺ influx and apoptotic cell death. Further electrophysiological recording demonstrated that CNCP directly activated TRPC6 channels by increasing channel open probability with an EC₅₀ value of 6.01 μM. Considered together, these data demonstrate that the direct activation of TRPC6 channels contributes to CNCP-induced apoptotic cell death in HK-2 cells. Our data point out the potential risk of renal toxicity from CNCP if used as a therapeutic agent.

Degradable and Injectable Hydrogel for Drug Delivery in Soft Tissues

Injectable hydrogels are promising platforms for tissue engineering and local drug delivery as they allow minimal invasiveness. We have here developed an injectable and biodegradable hydrogel based on an amphiphilic PNIPAAm- b-PLA- b-PEG- b-PLA- b-PNIPAAm pentablock copolymer synthesized by ring-opening polymerization/nitroxide-mediated polymerization (ROP/NMP) combination. The hydrogel formation at around 30 °C was demonstrated to be mediated by intermicellar bridging through the PEG central block. Such a result was particularly highlighted by the inability of a PEG- b-PLA- b-PNIPAAm triblock analog of the same composition to gelify. The hydrogels degraded through hydrolysis of the PLA esters until complete mass loss due to the diffusion of the recovered PEG and PNIPAAm/micelle based residues in the solution. Interestingly, hydrophobic molecules such as riluzole (neuroprotective drug) or cyanine 5.5 (imaging probe) could be easily loaded in the hydrogels' micelle cores by mixing them with the copolymer solution at room temperature. Drug release was correlated to polymer mass loss. The hydrogel was shown to be cytocompatible (neuronal cells, in vitro) and injectable through a small-gauge needle (in vivo in rats). Thus, this hydrogel platform displays highly attractive features for use in brain/soft tissue engineering as well as in drug delivery.

TRPs in Tox: Involvement of Transient Receptor Potential-Channels in Chemical-Induced Organ Toxicity-A Structured Review

Chemicals can exhibit significant toxic properties. While for most compounds, unspecific cell damaging processes are assumed, a plethora of chemicals exhibit characteristic odors, suggesting a more specific interaction with the human body. During the last few years, G-protein-coupled receptors and especially chemosensory ion channels of the transient receptor potential family (TRP channels) were identified as defined targets for several chemicals. In some cases, TRP channels were suggested as being causal for toxicity. Therefore, these channels have moved into the spotlight of toxicological research. In this review, we screened available literature in PubMed that deals with the role of chemical-sensing TRP channels in specific organ systems. TRPA1, TRPM and TRPV channels were identified as essential chemosensors in the nervous system, the upper and lower airways, colon, pancreas, bladder, skin, the cardiovascular system, and the eyes. Regarding TRP channel subtypes, A1, M8, and V1 were found most frequently associated with toxicity. They are followed by V4, while other TRP channels (C1, C4, M5) are only less abundantly expressed in this context. Moreover, TRPA1, M8, V1 are co-expressed in most organs. This review summarizes organ-specific toxicological roles of TRP channels.

Toxicodynamics of Lead, Cadmium, Mercury and Arsenic- induced kidney toxicity and treatment strategy: A mini review

Environmental pollution has become a concerning matter to human beings. Flint water crisis in the USA pointed out that pollution by heavy metal is getting worse day by day, predominantly by Lead, Cadmium, Mercury and Arsenic. Despite of not having any biological role in flora and fauna, they exhibit detrimental effect following exposure (acute or chronic). Even at low dose, they affect brain, kidney and heart. Oxidative stress has been termed as cause and effect in heavy metal-induced kidney toxicity. In treatment strategy, different chelating agent, vitamins and minerals are included, though chelating agents has been showed different fatal drawbacks. Interestingly, plants and plants derived compounds had shown possible effectiveness against heavy metals induced kidney toxicity. This review will provide detail information on toxicodynamics of Pb, Cd, Hg and As, treatment strategy along with the possible beneficiary role of plant derived compound to protect kidney.

Vitamin D alleviates lead induced renal and testicular injuries by immunomodulatory and antioxidant mechanisms in rats

This study measured the effects of vitamin D (VD) supplementation on the underlying molecular pathways involved in renal and testicular damage induced by lead (Pb) toxicity. Thirty two adult male Wistar rats were divided equally into four groups that were treated individually or simultaneously, except the negative control, for four weeks with lead acetate in drinking water (1,000 mg/L) and/or intramuscular VD (1,000 IU/kg; 3 days/week). Pb toxicity markedly reduced serum VD and Ca²⁺, induced substantial renal and testicular injuries with concomitant significant alterations in the expression of VD metabolising enzymes, its receptor and binding protein, and the calcium sensing receptor. Pb also significantly promoted lipid peroxidation and pro-inflammatory cytokines (IL-4 and TNF-α) in the organs of interest concomitantly with declines in several anti-oxidative markers (glutathione, glutathione peroxidase and catalase) and the anti-inflammatory cytokine, IL-10. The co-administration of VD with Pb markedly mitigated renal and testicular injuries compared with positive controls. This was associated with restoration of the expression of VD related molecules, promotion of anti-oxidative and anti-inflammatory markers, but tissue Pb concentrations were unaffected. In conclusion, this report is the first to reveal potential protective effects for VD against Pb-induced renal and testicular injuries via anti-inflammatory and anti-oxidative mechanisms.

Functional cooperation between KCa3.1 and TRPC1 channels in human breast cancer: Role in cell proliferation and patient prognosis

Intracellular Ca2⁺ levels are important regulators of cell cycle and proliferation. We, and others, have previously reported the role of KCa3.1 (KCNN4) channels in regulating the membrane potential and the Ca2⁺ entry in association with cell proliferation. However, the relevance of KC3.1 channels in cancer prognosis as well as the molecular mechanism of Ca2⁺ entry triggered by their activation remain undetermined. Here, we show that RNAi-mediated knockdown of KCa3.1 and/or TRPC1 leads to a significant decrease in cell proliferation due to cell cycle arrest in the G1 phase. These results are consistent with the observed upregulation of both channels in synchronized cells at the end of G1 phase. Additionally, knockdown of TRPC1 suppressed the Ca2⁺ entry induced by 1-EBIO-mediated KCa3.1 activation, suggesting a functional cooperation between TRPC1 and KCa3.1 in the regulation of Ca2⁺ entry, possibly within lipid raft microdomains where these two channels seem to co-localize. We also show significant correlations between KCa3.1 mRNA expression and poor patient prognosis and unfavorable clinical breast cancer parameters by mining large datasets in the public domain. Together, these results highlight the importance of KCa3.1 in regulating the proliferative mechanisms in breast cancer cells as well as in providing a promising novel target in prognosis and therapy.

Lead poisoning: acute exposure of the heart to lead ions promotes changes in cardiac function and Cav1.2 ion channels

Lead ions (Pb²⁺) possess characteristics similar to Ca²⁺. Because of this and its redox capabilities, lead causes different toxic effects. The neurotoxic effects have been well documented; however, the toxic effects on cardiac tissues remain allusive. We utilized isolated guinea pig hearts and measured the effects of Pb²⁺ on their contractility and excitability. Acute exposure to extracellular Pb²⁺ had a negative inotropic effect and increased diastolic tension. The speed of contraction and relaxation were affected, though the effects were more dramatic on the speed of contraction. Excitability was also altered. Heart beat frequency increased and later diminished after lead ion exposure. Pro-arrhytmic events, such as early after-depolarization and a reduction of the action potential plateau, were also observed. In isolated cardiomyocytes and tsA 201 cells, extracellular lead blocked currents through Cav1.2 channels, diminished their activation, and enhanced their fast inactivation, negatively affecting their gating currents. Thus, Pb²⁺ was cardiotoxic and reduced cardiac contractility, making the heart prone to arrhythmias. This was due, in part, to Pb²⁺ effects on the Cav1.2 channels; however, other channels, transporters or pathways may also be involved. Acute cardiotoxic effects were observed at Pb²⁺ concentrations achievable during acute lead poisoning. The results suggest how Cav1.2 gating can be affected by divalent cations, such as Pb², and also suggest a more thorough evaluation of heart function in individuals affected by lead poisoning.