Cadmium activates CaMK-II and initiates CaMK-II-dependent apoptosis in mesangial cells

Cx43 overexpression reduce the incidence of obstructive sleep apnea associated atrial fibrillation via the CaMKⅡγ/HIF-1 axis

BACKGROUND

Previous studies by our group have demonstrated chronic intermittent hypoxia (CIH) can decrease connexin 43 (Cx43) protein expression and thus increase atrial fibrillation (AF) inducibility. Cardiac sympathetic denervation (CSD) can reduce AF and increase Cx43 expression, however, the underlying molecular mechanisms and signaling pathways are still unclear.

METHODS AND RESULTS

An obstructive sleep apnea (OSA) rat model in vivo experiments and CIH H9c2 cells model in vitro experiments were used to figure out the roles and underlying mechanisms of Cx43 on OSA-associated AF. In this study, we examined the expression of Cx43, CaMKⅡγ, Bax, Caspase 3, HIF-1 Bcl-2, Tunel, and CPB/p300, to discover the association between proteins and the mechanism of regulatory changes. The downstream proteins of Cx43 were calculated by gene sequencing and data analysis. We found Cx43 expression was significantly downregulated after CIH exposure in rat and H9c2 cells. Active caspase-3 and Bax at CIH+8 h group are high, but decreased at OE+8 h group. The Bcl-2 expression was higher in the N and OE+8 h group than CIH+8 h group. TUNEL-positive cells from the CIH+8 h group was markedly higher. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses indicated Cx43 overexpression inhibited the CaMKIIγ expression, and CaMKIIγ was involved in the HIF-1 signaling pathway. In addition, we also found Cx43 overexpression remarkably decreased the HIF-1 protein and p300 mRNA expression, which inhibits the CaMKIIγ/HIF-1 signaling pathway.

CONCLUSIONS

Taken together, these results suggested Cx43 overexpression inhibits the expression of calcium/calmodulin dependent protein CaMKⅡγ via the Cx43/CaMKIIγ/HIF-1 axis, which finally reduces the myocardial apoptosis and incidence of AF.

The role of calcium, Akt and ERK signaling in cadmium-induced hair cell death

Exposure to heavy metals has been shown to cause damage to a variety of different tissues and cell types including hair cells, the sensory cells of our inner ears responsible for hearing and balance. Elevated levels of one such metal, cadmium, have been associated with hearing loss and shown to cause hair cell death in multiple experimental models. While the mechanisms of cadmium-induced cell death have been extensively studied in other cell types they remain relatively unknown in hair cells. We have found that calcium signaling, which is known to play a role in cadmium-induced cell death in other cell types through calmodulin and CaMKII activation as well as IP3 receptor and mitochondrial calcium uniporter mediated calcium flow, does not appear to play a significant role in cadmium-induced hair cell death. While calmodulin inhibition can partially protect hair cells this may be due to impacts on mechanotransduction activity. Removal of extracellular calcium, and inhibiting CaMKII, the IP3 receptor and the mitochondrial calcium uniporter all failed to protect against cadmium-induced hair cell death. We also found cadmium treatment increased pAkt levels in hair cells and pERK levels in supporting cells. This activation may be protective as inhibiting these pathways enhances cadmium-induced hair cell death rather than protecting cells. Thus cadmium-induced hair cell death appears distinct from cadmium-induced cell death in other cell types where calcium, Akt and ERK signaling all promote cell death.

Epigenetic mechanisms of cadmium-induced nephrotoxicity

Cadmium (Cd) is a widespread toxic pollutant that affects millions of individuals worldwide. Cd exposure in humans occurs primarily through consumption of contaminated food and water, cigarette smoking, and industrial applications. The kidney proximal tubular (PT) epithelial cells are the primary target of Cd toxicity. Cd-induced injury to PT cells impedes tubular reabsorption. Despite the many long-term sequelae of Cd exposure, molecular mechanisms of Cd toxicity are poorly understood, and no specific therapies exist to mitigate the effects of Cd exposure. In this review, we summarize recent work linking Cd-mediated damage to epigenetic perturbations - DNA methylation, and levels of histone modifications, including methylation and acetylation. New insights into the links between Cd intoxication and epigenetic damage will contribute to an improved understanding of Cd's pleiotropic impacts on cells, and perhaps lead to new, mechanism-based treatments for this condition.

The role of autophagy in cadmium-induced acute toxicity in glomerular mesangial cells and tracking polyubiquitination of cytoplasmic p53 as a biomarker

Cadmium (Cd) is a highly toxic environmental pollutant that can severely damage the kidneys. Here, we show that Cd-induced apoptosis is promoted by the cytoplasmic polyubiquitination of p53 (polyUb-p53), which is regulated by the polyubiquitination of SQSTM1/p62 (polyUb-p62) and autophagy in mouse kidney mesangial cells (MES13E cells). p53 was detected in monomeric and different high-molecular-weight (HMW) forms after Cd exposure. Monomeric p53 levels decreased in a concentration- and time-dependent manner. HMW-p53 transiently accumulated in the cytoplasm independent of proteasome inhibition. The expression patterns of p53 were similar to those of p62 upon Cd exposure, and the interactions between polyUb-p53 and polyUb-p62 were observed using immunoprecipitation. P62 knockdown reduced polyUb-p53 and upregulated nuclear monomeric p53, whereas p53 knockdown reduced polyUb-p62. Autophagy inhibition induced by ATG5 knockdown reduced Cd-induced polyUb-p62 and polyUb-p53 but upregulated the levels of nuclear p53. Pharmacological inhibition of autophagy by bafilomycin A1 increased polyUb-p62 and polyUb-p53 in the cytoplasm, indicating that p53 protein levels and subcellular localization were regulated by polyUb-p62 and autophagy. Immunoprecipitation and immunofluorescence revealed an interaction between p53 and LC3B, indicating that p53 was taken up by autophagosomes. Cd-resistant RMES13E cells and kidney tissues from mice continuously injected with Cd had reduced polyUb-p53, polyUb-p62, and autophagy levels. Similar results were observed in renal cell carcinoma cell lines. These results indicate that cytoplasmic polyUb-p53 is a potential biomarker for Cd-induced acute toxicity in mesangial cells. In addition, upregulation of nuclear p53 may protect cells against Cd cytotoxicity, but abnormal p53 accumulation may contribute to tumor development.

The cellular localization and chemical modification of a protein that acts as a critical safeguard against cellular damage may directly contribute to the toxic effects of cadmium. P53 is an essential tumor suppressor that is also involved in numerous other important biological functions. Ki-Tae Jung and Seon-Hee Oh of Chosun University, Gwangju, South Korea have now demonstrated that this protein also undergoes rapid changes in response to the environmental pollutant cadmium. P53 normally manages gene expression in the nucleus, but the authors found that it is rapidly shuttled to the cytoplasm and subjected to extensive chemical modification in cadmium-treated cultured kidney cells. This relocation appears to contribute directly to subsequent cell death, and the authors suggest that this P53 response could be an important biomarker for diagnosing human cadmium exposure.

Synoviocytes from pigmented villonodular synovitis are less sensitive to cadmium-induced cell death than synoviocytes from rheumatoid arthritis

Pigmented villonodular synovitis (PVNS) is a rare inflammatory articular disease sharing common characteristics with rheumatoid arthritis (RA), notably hyperplasia of the synovium due to a hyperproliferation of synoviocytes, and with cancer owing to mutations of the CSF1/M-CCSF gene. Targeting synovium hyperplasia by the local delivery of Cadmium (Cd) has been already tested in vitro and in vivo models of RA and could be applied to PVNS. PVNS and RA synoviocytes were exposed to low doses of Cd. After different culture time points, a qualitative analysis was done by microscopy and quantitative measurements of apoptosis, cell viability and IL-6 production were carried. IL-6 production by PVNS synovial tissue was also quantified after Cd treatment with or without the presence of pro-inflammatory cytokines (IL-17 + TNF). Addition of Cd induced cell death in both PVNS (1 ppm) and RA (0.1 ppm) synoviocytes, which increased with time and Cd concentrations. Cd increased the percentage of apoptotic cells and decreased cell viability and IL-6 production. In all these experiments, PVNS synoviocytes were tenfold less sensitive to Cd than RA synoviocytes. Cd decreased IL-6 production by PVNS synovial tissue and its effect was enhanced with pro-inflammatory cytokines. In summary, PVNS synoviocytes show resistance to Cd-induced cell death and decreased inflammation. Intra-articular use of Cd could represent a potential therapeutic tool in PVNS.

Potentilla anserine L. polysaccharide protects against cadmium-induced neurotoxicity

Cadmium is a toxic metal that can damage the brain and other organs. This study aimed to explore the protective effects of Potentilla anserine L. polysaccharide (PAP) against CdCl2-induced neurotoxicity in N2a and SH-SY5Y cells and in the cerebral cortex of BALB/c mice. In addition, we aimed to identify the potential mechanisms underlying these protective effects. Relative to CdCl2 treatment alone, pretreatment with PAP prevented the reduction in cell viability evoked by CdCl2, decreased rates of apoptosis, promoted calcium homeostasis, decreased ROS accumulation, increased mitochondrial membrane potential, inhibited cytochrome C and AIF release, and prevented the cleavage of caspase-3 and PARP. In addition, PAP significantly decreased the CdCl2-induced phosphorylation of CaMKII, Akt, and mTOR. In conclusion, PAP represents a potential therapeutic agent for the treatment of Cd-induced neurotoxicity, functioning in part via attenuating the activation of the mitochondrial apoptosis pathway and the Ca2+-CaMKII-dependent Akt/mTOR pathway.

Osteosarcoma in Children: Not Only Chemotherapy

Osteosarcoma (OS) is the most severe bone malignant tumor, responsible for altered osteoid deposition and with a high rate of metastasis. It is characterized by heterogeneity, chemoresistance and its interaction with bone microenvironment. The 5-year survival rate is about 67% for patients with localized OS, while it remains at 20% in case of metastases. The standard therapy for OS patients is represented by neoadjuvant chemotherapy, surgical resection, and adjuvant chemotherapy. The most used chemotherapy regimen for children is the combination of high-dose methotrexate, doxorubicin, and cisplatin. Considered that the necessary administration of high-dose chemotherapy is responsible for a lot of acute and chronic side effects, the identification of novel therapeutic strategies to ameliorate OS outcome and the patients' life expectancy is necessary. In this review we provide an overview on new possible innovative therapeutic strategies in OS.

A new perspective on calmodulin-regulated calcium and ROS homeostasis upon carbon black nanoparticle exposure

Toxicological studies propose that exposure to carbon black nanoparticles induces organ injuries and inflammatory responses. Besides, current understanding of the molecular mechanisms implies that carbon black nanoparticles (CBNP) exposure induces the production of reactive oxygen species (ROS) causing inflammation, mitochondrial dysfunction or disturbance in calcium homeostasis. However, the precise mechanisms whereby CBNP exert these effects in the lung are still not fully understood. To gain insight into the possible mechanism of CBNP exerted toxicity, human alveolar epithelial cells (A549) were exposed to different concentrations of CBNP and for different timepoints. The reaction of the cells was monitored by the systematic use of cell-based measurements of calcium and ROS, in the presence and absence of calcium (Ca²⁺) pump inhibitors/chelators and antioxidants. Followed by an in-depth PCR analysis of 84 oxidative stress-related genes. The measurements revealed, as compared to the control, that exposure to CBNP nanoparticles leads to the generation of high ROS levels, as well as a disturbance in calcium homeostasis, which remained primarily unchanged even after 24 h of exposure. Nevertheless, in presence of antioxidants N-acetylcysteine (NAC) and Trolox, ROS formation was considerably reduced without affecting the intracellular calcium concentration. On the other hand, Ca²⁺ pump inhibitors/chelators, BAPTA (1,2-bis(o-amino phenoxy)ethane-N, N, N′, N′-tetraacetic acid) and verapamil not only decreased the Ca²⁺ overload, but also further decreased the ROS formation, indicating its role in CBNP-induced oxidative stress. Further, a PCR array analysis of A549 cells in presence and absence of the calmodulin (CaM) antagonist W7, indicated toward nine altered oxidative stress-related genes which further confirmed our cytotoxicity results. Obtained data suggested that CBNP exposure elevates calcium ion concentration, which further contributes to oxidative stress, via the calcium-binding protein CaM. Its inhibition with W7 leads to downregulation in gene expression of nine oxidative stress-related genes, which otherwise, as compared to control, show increased gene expression. The results of the study thus confirm that exposure of lung epithelial cells to CBNP leads to oxidative stress; however, the oxidative stress itself is a result of a disturbance in both calcium and ROS homeostasis, and should be considered while searching for a new strategy for prevention of CBNP-induced lung toxicity.

DCMQA, a caffeoylquinic acid derivative alleviates NMDA-induced neurotoxicity via modulating GluN2A and GluN2B-containing NMDA receptors in vitro

Compound DCMQA (4, 5-O-dicaffeoyl-1-O-[4-malic acid methyl ester]-quinic acid) is a natural caffeoylquinic acid derivative isolated from Arctium lappa L. roots. Caffeoylquinic acid derivatives have been reported to possess neuroprotective effects through inhibiting oxidative stress and apoptosis in vitro. However, whether DCMQA exerts protective effects on N-methyl-D-aspartate (NMDA)-induced neurotoxicity and the underlying mechanism has not been elucidated. In this study, the results indicated that pretreatment of DCMQA prevented the loss of cell viability and attenuated the LDH leakage in SH-SY5Y cells exposed to NMDA. Hoechst 33342 staining and Annexin V-PI double staining illustrated that DCMQA suppressed NMDA-induced morphological damage and neuronal apoptosis. Moreover, DCMQA inhibited NMDA-mediated Ca²⁺ influx, excessive intracellular ROS generation and loss of mitochondrial membrane potential (MMP). Western blot analysis showed that DCMQA attenuated the Bax/Bcl-2 ratio, release of cytochrome c as well as expression of caspase-9 and caspase-3. Besides, DCMQA down-regulated GluN2B-containing NMDA receptors (NMDARs) and up-regulated GluN2A-containing NMDARs, promoted the disruption of nNOS and PSD95 as well as activation of CaMK II-α. Furthermore, computational docking study indicated that DCMQA possessed a good affinity for NMDARs. These results indicated that DCMQA protects SH-SY5Y cells against NMDA-induced neuronal damage. In addition, the underlying mechanisms of DCMQA-mediated neuroprotection are associated with modulating NMDARs and disruption of nNOS-PSD95 as well as the activation of CaMK II-α.

Rapamycin inhibits B-cell activating factor (BAFF)-stimulated cell proliferation and survival by suppressing Ca2+-CaMKII-dependent PTEN/Akt-Erk1/2 signaling pathway in normal and neoplastic B-lymphoid cells

B-cell activating factor (BAFF) is a crucial survival factor for B cells, and excess BAFF contributes to development of autoimmune diseases. Recent studies have shown that rapamycin can prevent BAFF-induced B-cell proliferation and survival, but the underlying mechanism remains to be elucidated. Here we found that rapamycin inhibited human soluble BAFF (hsBAFF)-stimulated cell proliferation by inducing G₁-cell cycle arrest, which was through downregulating the protein levels of CDK2, CDK4, CDK6, cyclin A, cyclin D1, and cyclin E. Rapamycin reduced hsBAFF-stimulated cell survival by downregulating the levels of anti-apoptotic proteins (Mcl-1, Bcl-2, Bcl-xL and survivin) and meanwhile upregulating the levels of pro-apoptotic proteins (BAK and BAX). The cytostatic and cytotoxic effects of rapamycin linked to its attenuation of hsBAFF-elevated intracellular free Ca²⁺ ([Ca²⁺]_i). In addition, rapamycin blocked hsBAFF-stimulated B-cell proliferation and survival by preventing hsBAFF from inactivating PTEN and activating the Akt-Erk1/2 pathway. Overexpression of wild type PTEN or ectopic expression of dominant negative Akt potentiated rapamycin's suppression of hsBAFF-induced Erk1/2 activation and proliferation/viability in Raji cells. Interestingly, PP242 (mTORC1/2 inhibitor) or Akt inhibitor X, like rapamycin (mTORC1 inhibitor), reduced the basal or hsBAFF-induced [Ca²⁺]_i elevations. Chelating [Ca²⁺]_i with BAPTA/AM, preventing [Ca²⁺]_i elevation using EGTA, 2-APB or verapamil, inhibiting CaMKII with KN93, or silencing CaMKII strengthened rapamycin's inhibitory effects. The results indicate that rapamycin inhibits BAFF-stimulated B-cell proliferation and survival by blunting mTORC1/2-mediated [Ca²⁺]_i elevations and suppressing Ca²⁺-CaMKII-dependent PTEN/Akt-Erk1/2 signaling pathway. Our finding underscores that rapamycin may be exploited for prevention of excessive BAFF-induced aggressive B-cell malignancies and autoimmune diseases.

Cadmium-calcium interference in the Rhinella arenarum oviduct

Given that the cadmium (Cd) toxicity could be due to its interference with the calcium (Ca) homeostasis, the aim of this work was to study the effect of Cd over the presence, distribution and volume density (Vv) of Ca and Ca-ATPase in the secretory cells of the pars preconvoluta (PPC) and the pars convoluta (pc) in Rhinella arenarum. The severe effect of the xenobiotic (CdCl₂ 2.5 mg/kg) in sexually matured females was evaluated. Co-localization, as well as a marked reduction of Ca and Ca-ATPase, was observed in treated animals, in the areas analyzed, compared to control. Low calcium deposits were found in the secreting granules (SG) of the epithelial (ESC) and glandular secretory cells (GSC), while an increase in their cytoplasm and intracellular space was observed. The Ca-ATPase in treated and control animals was detected at the SG and the plasmatic membrane of the ESC and GSC. In relation to the Vv estimates, a substantial reduction of Ca deposits and Ca-ATPase activity was observed in the treated group, with respect to the control. Both amounts of Vv of Ca and Ca-ATPase activity were higher in PPC than in pc, and, higher in ESC than in GSC. These results were associated with the Cd concentration in the oviductal PC, determining that it is a bioaccumulator organ. Thus, this work demonstrated that the Cd interacted with Ca-ATPase, leading to an increase of cytosolic Ca, which is responsible for the possible disruptions in cellular metabolism.

Calcium/calmodulin-dependent protein kinase II regulates mammalian axon growth by affecting F-actin length in growth cone

While axon regeneration is a key determinant of functional recovery of the nervous system after injury, it is often poor in the mature nervous system. Influx of extracellular calcium (Ca²⁺ ) is one of the first phenomena that occur following axonal injury, and calcium/calmodulin-dependent protein kinase II (CaMKII), a target substrate for calcium ions, regulates the status of cytoskeletal proteins such as F-actin. Herein, we found that peripheral axotomy activates CaMKII in dorsal root ganglion (DRG) sensory neurons, and inhibition of CaMKII impairs axon outgrowth in both the peripheral and central nervous systems (PNS and CNS, respectively). Most importantly, we also found that the activation of CaMKII promotes PNS and CNS axon growth, and regulatory effects of CaMKII on axon growth occur via affecting the length of the F-actin. Thus, we believe our findings provide clear evidence that CaMKII is a critical modulator of mammalian axon regeneration.

BmK NT1-induced neurotoxicity is mediated by PKC/CaMKⅡ-dependent ERK1/2 and p38 activation in primary cultured cerebellar granule cells

Voltage-gated sodium channels (VGSCs) represent molecular targets for a number of potent neurotoxins that affect the ion permeation or gating kinetics. BmK NT1, an α-scorpion toxin purified from Buthus martensii Karch (BMK), induces excitatory neurotoxicity by activation of VGSCs with subsequent overloading of intracellular Ca²⁺ in cerebellar granule cells (CGCs). In the current study, we further investigated signaling pathways responsible for BmK NT1-induced neurotoxicity in CGCs. BmK NT1 exposure induced neuronal death in different development stages of CGCs with similar potencies ranging from 0.21-0.48 μM. The maximal neuronal death induced by BmK NT1 gradually increased from 25.6% at 7 days in vitro (DIVs) to 42.1%, 47.8%, and 67.2% at 10, 13, and 16 DIVs, respectively, suggesting that mature CGCs are more vulnerable to BmK NT1 exposure. Application of Ca²⁺/calmodulin-dependent protein kinase Ⅱ (CaMKⅡ) inhibitors, KN-62 or KN-93, but not Ca²⁺/calmodulin-dependent protein kinase kinase (CaMKK) inhibitor, STO-609, completely abolished BmK NT1-induced neuronal death. Moreover, BmK NT1 exposure stimulated CaMKⅡ phosphorylation. BmK NT1 also stimulated extracellular regulated protein kinases 1/2 (ERK1/2) and p38 phosphorylation which was abolished by tetrodotoxin demonstrating the role of VGSCs on BmK NT1-induced ERK1/2 and p38 phosphorylation. However, BmK NT1 didn't affect c-Jun N-terminal kinase (JNK) phosphorylation. In addition, both ERK1/2 inhibitor, U0126 and p38 inhibitor, SB203580 attenuated BmK NT1-induced neuronal death. Both PKC inhibitor, Gö 6983 and CaMKⅡ inhibitor, KN-62 abolished BmK NT1-induced ERK1/2 and p38 phosphorylation. Considered together, these data demonstrate that BmK NT1-induced neurotoxicity is through PKC/CaMKⅡ mediated ERK1/2 and p38 activation.

HIV-1 Nef physically associate with CAMKIIδ - ASK-1 complex to inhibit p38MAPK signalling and apoptosis in infected cells

Human immunodeficiency type 1 virus accessory protein Nef is a key modulator of AIDS pathogenesis. With no enzymatic activity, Nef regulated functions in host cells largely depends on its ability to form multi-protein complex with the cellular proteins. Here, we identified Calcium (Ca²⁺)/Calmodulin dependent protein kinase II subunit delta (CAMKIIδ) as novel Nef interacting host protein. Further, we confirmed that Nef mediated [Ca²⁺]_I promote formation of Nef-CAMKIIδ - apoptosis signal-regulating kinase (ASK-1) heterotrimeric complex. The assembly of Nef with CAMKIIδ - ASK-1 inhibits the downstream p38MAPK phosphorylation resulting in abrogation of apoptosis. Further, using competitive peptide inhibitors against Nef binding domains to CAMKIIδ, identified in the present study and ASK-1, individually blocked physical interaction of Nef with CAMKIIδ-ASK-1 complex and restored p38MAPK phosphorylation and apoptosis. Altogether, our study indicates that HIV-Nef modulates cytosolic [Ca²⁺]_I and blocks CAMKIIδ - ASK-1 kinase activity to inhibit apoptosis of infected cells.

BAFF inhibits autophagy promoting cell proliferation and survival by activating Ca2+-CaMKII-dependent Akt/mTOR signaling pathway in normal and neoplastic B-lymphoid cells

B cell activating factor from the TNF family (BAFF) is implicated in not only the physiology of normal B cells, but also the pathophysiology of aggressive B cells related to malignant and autoimmune diseases. Autophagy plays a crucial role in balancing the beneficial and detrimental effects of immunity and inflammation. However, little is known about whether and how excessive BAFF mediates autophagy contributing to B-cell proliferation and survival. Here, we show that excessive human soluble BAFF (hsBAFF) inhibited autophagy with a concomitant reduction of LC3-II in normal and B-lymphoid (Raji) cells. Knockdown of LC3 not only potentiated hsBAFF inhibition of autophagy, but also attenuated hsBAFF activation of Akt/mTOR pathway, thereby diminishing hsBAFF-induced B-cell proliferation/viability. Further, we found that hsBAFF inhibition of autophagy was Akt/mTOR-dependent. This is supported by the findings that hsBAFF increased mTORC1-mediated phosphorylation of ULK1 (Ser757); Akt inhibitor X, mTORC1 inhibitor rapamycin, mTORC1/2 inhibitor PP242, expression of dominant negative Akt, or knockdown of mTOR attenuated hsBAFF-induced phosphorylation of ULK1, decrease of LC3-II level, and increase of cell proliferation/viability. Chelating intracellular free Ca²⁺ ([Ca²⁺]_i) with BAPTA/AM or preventing [Ca²⁺]_i elevation using EGTA or 2-APB profoundly blocked hsBAFF-induced activation of Akt/mTOR, phosphorylation of ULK1 and decrease of LC3-II, as well as increase of cell proliferation/viability. Similar effects were observed in the cells where CaMKII was inhibited by KN93 or knocked down by CaMKII shRNA. Collectively, these results indicate that hsBAFF inhibits autophagy promoting cell proliferation and survival through activating Ca²⁺-CaMKII-dependent Akt/mTOR signaling pathway in normal and neoplastic B-lymphoid cells. Our findings suggest that manipulation of intracellular Ca²⁺ level or CaMKII, Akt, or mTOR activity to promote autophagy may be exploited for prevention of excessive BAFF-induced aggressive B lymphocyte disorders and autoimmune diseases.

Characterization of calmodulin in the clam Anodonta woodiana: differential expressions in response to environmental Ca2+ and Cd2+

Aims

To explore effect of Ca2+ and Cd2+ on the calmodulin (CaM), one complete cDNA sequence (AwCaM1) was cloned and characterized from the freshwater mussel Anodonta woodiana and its expressions were analyzed.

Materials and methods

The AwCaM1 was cloned from the A. woodiana using the rapid amplification of cDNA ends methods and its expression was determined by real-time PCR.

Results

In the hepatopancreas, AwCaM1 expression was up-regulated with a time and dose dependent pattern in the Ca2+ treated groups (0.01, 0.02, 0.04 and 0.08 mg/L) during experiment observed, and increased more than 56.15% (p<0.05) compared with that of control group. AwCaM1 mRNA level increased more 65.04% (p<0.05) in the Cd2+ treated groups (8 and 16 mg/L). In the gill, AwCaM1 expression increased more than 79.41% (p<0.05) compared with that of control group in all the Ca2+ treated groups, and more than 88.23% (p<0.05) in all the Cd2+ treated groups.

Conclusion

These results indicated that up-regulations of AwCaM1 expression in bivalve A. woodiana are associated with Ca2+ absorb and environmental adaption derived from Ca2+ and Cd2+ treatment.

CaMKⅡ mediates cadmium induced apoptosis in rat primary osteoblasts through MAPK activation and endoplasmic reticulum stress

Ca²⁺ is an important ion in various intracellular metabolic pathways. Endoplasmic reticulum (ER) is a major intracellular calcium store and ER calcium homeostasis plays a key part in the regulation of apoptosis. We have previously shown that Cadmium (Cd) induces apoptosis in osteoblasts (OBs), accompany by increased cytoplasmic calcium. As the role of calcium in OBs apoptosis induced by Cd has not been clarified we investigated the effects of Cd exposure in rat OBs on intracellular Ca²⁺, CaMKII phosphorylation, and the pathways implicated in inducing apoptosis. The results showed that cadmium(Cd) induced elevation of intracellular Ca²⁺ ([Ca²⁺]_i) in OBs by the release of Ca²⁺ from ER and the inflow of Ca²⁺ from the extracellular matrix. Cd induced [Ca²⁺]_i elevation and phosphorylation of CaMKII which might be involved in activation of MAPKs and participated in Cd-induced mitochondrial apoptosis through the alteration of the ratio of Bax/Bcl-2 expression. Meanwhile, CaMKII phosphorylation activated unfolded protein response (UPR) during cadmium treatment and could enable the ER apoptosis pathway through the activation of caspase-12. These results indicated that CaMKII plays an important role in Cd induced ER apoptosis and MAPK activation. Our data provide new insights into the mechanisms underlying apoptosis in OBs following Cd exposure. This provides a theoretical basis for future investigations into the clinical therapeutic application of CaMKⅡ inhibitors in osteoporosis induced by Cd exposure.

Cadmium favors F-actin depolymerization in rat renal mesangial cells by site-specific, disulfide-based dimerization of the CAP1 protein

Cadmium is a toxic metal that produces oxidative stress and has been shown to disrupt the actin cytoskeleton in rat renal mesangial cells (RMC). In a survey of proteins that might undergo Cd2+-dependent disulfide crosslinking, we identified the adenylyl cyclase-associated protein, CAP1, as undergoing a dimerization in response to Cd2+ (5-40 µM) that was sensitive to disulfide reducing agents, was reproduced by the disulfide crosslinking agent diamide, and was shown by site-directed mutagenesis to involve the Cys29 residue of the protein. Reactive oxygen species are not involved in the thiol oxidation, and glutathione modulates background levels of dimer. CAP1 is known to enhance cofilin's F-actin severing activity through binding to F-actin and cofilin. F-actin sedimentation and GST-cofilin pulldown studies of CAP1 demonstrated enrichment of the CAP1 dimer's association with cofilin, and in the cofilin-F-actin pellet, suggesting that Cd2+-induced dimer increases the formation of a CAP1-cofilin-F-actin complex. Both siRNA-based silencing of CAP1 and overexpression of a CAP1 mutant lacking Cys29 (and therefore, incapable of dimerization in response to Cd2+) increased RMC viability and provided some protection of F-actin structures against Cd2+. It is concluded that Cd2+ brings about disruption of the RMC cytoskeleton in part through formation of a CAP1 dimer that increases recruitment of cofilin to F-actin filaments.

Activation of Ca2+-sensing receptor as a protective pathway to reduce Cadmium-induced cytotoxicity in renal proximal tubular cells

Cadmium (Cd), as an extremely toxic metal could accumulate in kidney and induce renal injury. Previous studies have proved that Cd impact on renal cell proliferation, autophagy and apoptosis, but the detoxification drugs and the functional mechanism are still in study. In this study, we used mouse renal tubular epithelial cells (mRTECs) to clarify Cd-induced toxicity and signaling pathways. Moreover, we proposed to elucidate the prevent effect of activation of Ca²⁺ sensing receptor (CaSR) by Calcimimetic (R-467) on Cd-induced cytotoxicity and underlying mechanisms. Cd induced intracellular Ca²⁺ elevation through phospholipase C-inositol 1, 4, 5-trisphosphate (PLC) followed stimulating p38 mitogen-activated protein kinases (MAPK) activation and suppressing extracellular signal-regulated kinase (ERK) activation, which leaded to increase apoptotic cell death and inhibit cell proliferation. Cd induced p38 activation also contribute to autophagic flux inhibition that aggravated Cd induced apoptosis. R-467 reinstated Cd-induced elevation of intracellular Ca²⁺ and apoptosis, and it also increased cell proliferation and restored autophagic flux by switching p38 to ERK pathway. The identification of the activation of CaSR-mediated protective pathway in renal cells sheds light on a possible cellular protective mechanism against Cd-induced kidney injury.

Protective effect of cadmium-induced autophagy in rat renal mesangial cells

Cadmium damages renal cells, and in particular may cause mesangial cell death by necrosis or apoptosis, depending on exposure conditions in cultured cells. However, there is an uncertainty as to whether Cd²⁺-induced autophagy can protect mesangial cells against these other mechanisms of cell death. We have used autophagy-incompetent mouse embryonic fibroblast (MEF) cells lacking the Atg16 gene, as well as cultured rat mesangial cells (RMC) in which Atg16 has been silenced, to examine this issue. Measuring the processing of LC3-I to LC3-II and expression of sequestosome-1 (p62), we define conditions under which RMC can be induced to undergo autophagy in response to 0-20 µM CdCl₂. Similarly, Cd²⁺ can initiate autophagy in MEF cells. However, when autophagy is compromised, either by gene knockout in MEF cells or by RNA silencing in RMC, cell viability is decreased, and concomitantly a Cd²⁺ dose-dependent increase in pro-caspase-3 cleavage indicates the initiation of apoptotic cell death. In contrast to some previous reports, Cd²⁺-induced autophagy is not correlated with increased levels of cellular reactive oxygen species but, among a panel of kinases investigated, is suppressed by inhibition of the Jun kinase. We conclude that concentrations of Cd²⁺ that initiate autophagy may afford renal mesangial cells some degree of protection against other modes (apoptosis, necrosis) of cell death.

Elevation of intracellular calcium and oxidative stress is involved in perfluorononanoic acid–induced neurotoxicity

Perfluorononanoic acid (PFNA) is one of the major perfluorinated compounds found in both biological and abiotic samples and has recently been demonstrated to cause neurobehavioral defects in mammals. In this study, pheochromocytoma-12 (PC12) cells were exposed to various doses of PFNA to explore the cytotoxicity of PFNA to neurons and the possible mechanisms underlying these effects. The results showed that exposure to PFNA dose-dependently decreased the viability of PC12 cells and increased the release of lactate dehydrogenase into cell culture media. Exposure to PFNA increased the malondialdehyde content and decreased the total antioxidant capacity and glutathione peroxidase activity in PC12 cell culture supernatants. Exposure to PFNA increased the intracellular calcium level and upregulated the Ca2+/calmodulin-dependent protein kinase II (CaMKII) expression in PC12 cells. PFNA also decreased Bcl-2 expression and increased Bax expression in PC12 cells. These results suggested that exposure to PFNA elevated the intracellular calcium level and activated the CaMKII signaling pathway, which may aggravate oxidative stress in PC12 cells and lead to cell damage or cell apoptosis.

Effect of fluoride exposure on mRNA expression of cav1.2 and calcium signal pathway apoptosis regulators in PC12 cells

This study investigated the effects of fluoride exposure on the mRNA expression of Cav1.2 calcium signaling pathway and apoptosis regulatory molecules in PC12 cells. The viability of PC12 cell receiving high fluoride (5.0mM) and low fluoride (0.5mM) alone or fluoride combined with L-type calcium channel (LTCC) agonist/inhibitor (5umol/L FPL6417/2umol/L nifedipine) was detected using cell counting kit-8 at different time points (2, 4, 6, 8, 12, 10, and 24h). Changes in the cell configuration were observed after exposing the cells to fluoride for 24h. The expression levels of molecules related to the LTCC were examined, particularly, Cav1.2, c-fos, CAMK II, Bax, and Bcl-2. Fluoride poisoning induced severe cell injuries, such as decreased PC12 cell activity, enhanced cell apoptosis, high c-fos, CAMKII, and Bax mRNA expression levels. Bcl-2 expression level was also reduced. Meanwhile, high fluoride, high fluoride with FPL64176, and low fluoride with FPL64176 enhanced the Cav1.2 expression level. In contrast, low fluoride, high fluoride with nifedipine, and low fluoride with nifedipine reduced the Cav1.2 expression level. Thus, Cav1.2 may be an important molecular target for the fluorosis treatment, and the LTCC inhibitor nifedipine may be an effective drug for fluorosis.

Tris (1,3-dichloro-2-propyl) phosphate induces toxicity by stimulating CaMK2 in PC12 cells

Tris (1,3-dichloro-2-propyl) phosphate (TDCIPP) is one of the widely used organophosphorus flame retardants (OPFRs), which are regarded as suitable substitutes for brominated flame retardants (BFRs). Previously, we have validated the toxicity of TDCIPP in PC12 cells owing to the induced alterations in GAP43, NF-H, CaMK2a/2b, and tubulin α/β proteins; however, limited information is currently available on the toxicity and mechanism of TDCIPP. In the present study, cytotoxicity effects were evaluated by exposing PC12 cells to different concentrations of TDCIPP (0-50 μM) for 4 days. To explore the possible mechanisms through which cytotoxicity is induced, changes in intracellular [Ca²⁺ ]_i levels and the activation of calmodulin dependent protein kinase 2 (CaMK2), c-Jun N-terminal kinase (JNK), extracellular regulated protein kinases (ERK1/2), and p38 mitogen-activated protein kinases (MAPK) pathways were evaluated. Furthermore, PC12 cells were pretreated with CaMK2 inhibitor KN93 to investigate the relationship between TDCIPP-induced phosphorylation of CaMK2 and activation of JNK, ERK1/2, and p38 MAPK pathways. Our results indicate that TDCIPP-induced toxicity might be associated with the overload of [Ca²⁺ ]_i levels, increased phosphorylation of CaMK2, and activation of the JNK, ERK1/2, and p38 MAPK pathways, the lattermost of which was further demonstrated to be partially elicited by the CaMK2 phosphorylation.

Chronic Kidney Disease and Exposure to Nephrotoxic Metals

Chronic kidney disease (CKD) is a common progressive disease that is typically characterized by the permanent loss of functional nephrons. As injured nephrons become sclerotic and die, the remaining healthy nephrons undergo numerous structural, molecular, and functional changes in an attempt to compensate for the loss of diseased nephrons. These compensatory changes enable the kidney to maintain fluid and solute homeostasis until approximately 75% of nephrons are lost. As CKD continues to progress, glomerular filtration rate decreases, and remaining nephrons are unable to effectively eliminate metabolic wastes and environmental toxicants from the body. This inability may enhance mortality and/or morbidity of an individual. Environmental toxicants of particular concern are arsenic, cadmium, lead, and mercury. Since these metals are present throughout the environment and exposure to one or more of these metals is unavoidable, it is important that the way in which these metals are handled by target organs in normal and disease states is understood completely.

Anti-proliferative, pro-apoptotic and anti-invasive effect of EC/EV system in human osteosarcoma

Osteosarcoma is the most common and aggressive bone tumor in children. The Endocannabinoid/Endovanilloid system has been proposed as anticancer target in tumor of different origins. This system is composed of two receptors (CB1 and CB2), the Transient Potential Vanilloid 1 (TRPV1) channel and their ligands and enzymes. CB1 is expressed mainly in central nervous system while CB2 predominantly on immune and peripheral cells. We investigated the effects of JWH-133 (CB2 agonist) and RTX (TRPV1 agonist) in six human Osteosarcoma cell lines: MG-63, U-2OS, MNNG/HOS, Saos-2, KHOS/NP, Hs888Lu, by Apoptosis and Migration-Assay. We also compared the effects of these compounds on Caspase-3, AKT, MMP-2 and Notch-1 regulation by Q-PCR and Western Blotting.

We observed an anti-proliferative, pro-apoptotic, anti-invasive effect. Our results show that both CB2 stimulation and TRPV1 activation, in different Osteosarcoma cell lines, can act on the same pathways to obtain the same effect, indicating the Endocannabinoid/Endovanilloid system as a new therapeutic target in Osteosarcoma.

Celastrol Attenuates Cadmium-Induced Neuronal Apoptosis via Inhibiting Ca2+ -CaMKII-Dependent Akt/mTOR Pathway

Cadmium (Cd), an environmental and industrial pollutant, affects the nervous system and consequential neurodegenerative disorders. Recently, we have shown that celastrol prevents Cd-induced neuronal cell death partially by suppressing Akt/mTOR pathway. However, the underlying mechanism remains to be elucidated. Here, we show that celastrol attenuated Cd-elevated intracellular-free calcium ([Ca²⁺ ]_i ) level and apoptosis in neuronal cells. Celastrol prevented Cd-induced neuronal apoptosis by inhibiting Akt-mediated mTOR pathway, as inhibition of Akt with Akt inhibitor X or ectopic expression of dominant negative Akt reinforced celastrol's prevention of Cd-induced phosphorylation of S6K1/4E-BP1 and cell apoptosis. Furthermore, chelating intracellular Ca²⁺ with BAPTA/AM or preventing [Ca²⁺ ]_i elevation using EGTA potentiated celastrol's repression of Cd-induced [Ca²⁺ ]_i elevation and consequential activation of Akt/mTOR pathway and cell apoptosis. Moreover, celastrol blocked Cd-elicited phosphorylation of CaMKII, and pretreatment with BAPTA/AM or EGTA enhanced celastrol's suppression of Cd-increased phosphorylation of CaMKII in neuronal cells, implying that celastrol hinders [Ca²⁺ ]_i -mediated CaMKII phosphorylation. Inhibiting CaMKII with KN93 or silencing CaMKII attenuated Cd activation of Akt/mTOR pathway and cell apoptosis, and this was strengthened by celastrol. Taken together, these data demonstrate that celastrol attenuates Cd-induced neuronal apoptosis via inhibiting Ca²⁺ -CaMKII-dependent Akt/mTOR pathway. Our findings underscore that celastrol may act as a neuroprotective agent for the prevention of Cd-induced neurodegenerative disorders. J. Cell. Physiol. 232: 2145-2157, 2017. © 2016 Wiley Periodicals, Inc.

Network-Based Approach to Identify Potential Targets and Drugs that Promote Neuroprotection and Neurorepair in Acute Ischemic Stroke

Acute ischemic stroke (AIS) accounts for more than 80% of the approximately 610,000 new stroke cases worldwide every year. Both ischemia and reperfusion can cause death, damage, and functional changes of affected nerve cells, and these alterations can result in high rates of disability and mortality. Therefore, therapies aimed at increasing neuroprotection and neurorepair would make significant contributions to AIS management. However, with regard to AIS therapies, there is currently a large gap between experimental achievements and practical clinical solutions (EC-GAP-AIS). Here, by integrating curated disease-gene associations and interactome network known to be related to AIS, we investigated the molecular network mechanisms of multi-module structures underlying AIS, which might be relevant to the time frame subtypes of AIS. In addition, the EC-GAP-AIS phenomenon was confirmed and elucidated by the shortest path lengths and the inconsistencies in the molecular functionalities and overlapping pathways between AIS-related genes and drug targets. Furthermore, we identified 23 potential targets (e.g. ADORA3, which is involved in the regulation of cellular reprogramming and the extracellular matrix) and 46 candidate drugs (e.g. felbamate, methylphenobarbital and memantine) that may have value for the treatment of AIS.

Pleiotropic roles of Ca+2/calmodulin-dependent pathways in regulating cadmium-induced toxicity in human osteoblast-like cell lines

The heavy metal cadmium is a widespread environmental contaminant that has gained public attention due to the global increase in cadmium-containing electronic waste. Human exposure to cadmium is linked to the pathogenesis of osteoporosis. We previously reported cadmium induces apoptosis and decreases alkaline phosphatase mRNA expression via extracellular signal-regulated protein kinase (ERK) activation in Saos-2 bone-forming osteoblasts. This study examines the mechanisms of cadmium-induced osteotoxicity by investigating roles of Ca⁺²/calmodulin-dependent protein kinase (CAMK) pathways. Saos-2 or MG-63 cells were treated for 24 or 48h with 5μM CdCl₂ alone or in combination with calmodulin-dependent phosphodiesterase (PDE) inhibitor CGS-9343β; calmodulin-dependent kinase kinase (CAMKK) inhibitor STO-609; or calmodulin-dependent kinase II (CAMKII) inhibitor KN-93. CGS-9343β protected against cadmium-induced toxicity and attenuated ERK activation; STO-609 enhanced toxicity and exacerbated ERK activation, whereas KN-93 had no detectable effect on cadmium-induced toxicity. Furthermore, CGS-9343β co-treatment attenuated cadmium-induced apoptosis; but CGS-9343β did not recover cadmium-induced decrease in ALP activity. The major findings suggest the calmodulin-dependent PDE pathway facilitates cadmium-induced ERK activation leading to apoptosis, whereas the CAMKK pathway plays a protective role against cadmium-induced osteotoxicity via ERK signaling. This research distinguishes itself by identifying pleiotropic roles for CAMK pathways in mediating cadmium's toxicity in osteoblasts.

Cadmium inhibits mouse sperm motility through inducing tyrosine phosphorylation in a specific subset of proteins

Cadmium (Cd) has been reported to impair male fertility, primarily by disrupting sperm motility, but the underlying molecular mechanism remains unclear. Here we investigated the effects of Cd on sperm motility, tyrosine phosphorylation, AMP-activated protein kinase (AMPK) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity, and ATP levels in vitro. Our results demonstrated that Cd inhibited sperm motility, GAPDH activity, AMPK activity and ATP production, and induced tyrosine phosphorylation of 55-57KDa proteins. Importantly, all the parameters affected by Cd were restored to normal levels when incubated with 10μM Cd in the presence of 30μM ethylene diamine tetraacetic acid (EDTA). Interestingly, changes of tyrosine phosphorylation levels of 55-57KDa proteins are completely contrary to that of other parameters. These results suggest that Cd-induced tyrosine phosphorylation of 55-57KDa proteins might act as an engine to block intracellular energy metabolism and thus decrease sperm motility.

Aluminum Chloride Induces Osteoblasts Apoptosis via Disrupting Calcium Homeostasis and Activating Ca(2+)/CaMKII Signal Pathway

Aluminum promotes osteoblast (OB) apoptosis. Apoptosis is induced by the disordered calcium homeostasis. Therefore, to investigate the relationship between Al-induced OB apoptosis and calcium homeostasis, calvarium OBs from neonatal rats (3-4 days) were cultured and exposed to 0.048-mg/mL Al(3+) or 0.048-mg/mL Al(3+) combined with 5 μM BAPTA-AM (OBs were pretreated with 5 μM BAPTA-AM for 1 h, then added 0.048 mg/mL Al(3+)), respectively. Then OB apoptosis rate, intracellular calcium ions concentration ([Ca(2+)]i), mRNA expression level of calmodulin (CaM), and protein expression levels of CaM and p-CaMKII in OBs were examined. The result showed that AlCl3 increased OB apoptosis rate, and [Ca(2+)]i and p-CaMKII expression levels and decreased CaM expression levels, whereas BAPTA-AM relieved the effects. These results proved that AlCl3 induced OB apoptosis by disrupting the intracellular Ca(2+) homeostasis and activating the Ca(2+)/CaMKII signal pathway. Our findings can provide new insights for revealing the apoptosis mechanism of OBs exposed to AlCl3.

Effect of TRPV1 combined with lidocaine on cell state and apoptosis of U87-MG glioma cell lines

OBJECTIVE

To study the effects of Transient receptor potential cation channel, subfamily V, member 1 (TRPV1) combined with lidocaine on status and apoptosis of U87-MG glioma cell line, and explore whether local anesthetic produces neurotoxicity by TRPV1.

METHODS

U87-MG cells were divided into control group, gene silencing group, empty vector group and TRPV gene up-regulation group. For cells in each group, flow cytometry was employed to detect the intracellular calcium ion concentration and mitochondrial membrane potential at different time point from cellular perspective. Cell apoptosis of U87-MG was assayed by flow cytometry and MTT from a holistic perspective.

RESULTS

Calcium ion concentration increased along with time. The concentration in TRPV1 gene up-regulation group was significantly higher than those in other groups at each time point (P < 0.05). After adding lidocaine, mitochondrial membrane potential in U87-MG significantly increased (P < 0.05). This increasing trend in TRPV1 gene up-regulation group was more significant than other groups (P < 0.05), while in TRPV1 gene silencing group, the trend significantly decreased (P < 0.05). Flow cytometry result and MTT result both showed that cell apoptosis in each group significantly increased after lidocaine was added (P < 0.05). This increasing trend in TRPV1 gene up-regulation group was more significant than other groups (P < 0.05), while in TRPV1 gene silencing group, the trend significantly decreased (P < 0.05). Moreover, apoptosis was more severe along with the increasing concentration of lidocaine (P < 0.05).

CONCLUSIONS

In this study, it was proved that lidocaine could dose-dependently induce the increase of intracellular calcium ion concentration, mitochondrial membrane potential and apoptosis in U87-MG glioma cell line. The up-regulation of TRPV1 enhanced cytotoxicity of lidocaine, which revealed the correlations between them. Lidocaine might have increased intracellular calcium ion concentration by activating TRPV1 gene and induced apoptosis of U87-GM glioma cell line by up-regulating mitochondrial membrane potential.

Cadmium Induces Apoptosis in Freshwater Crab Sinopotamon henanense through Activating Calcium Signal Transduction Pathway

Calcium ion (Ca²⁺) is one of the key intracellular signals, which is implicated in the regulation of cell functions such as impregnation, cell proliferation, differentiation and death. Cadmium (Cd) is a toxic environmental pollutant that can disturb cell functions and even lead to cell death. Recently, we have found that Cd induced apoptosis in gill cells of the freshwater crab Sinopotamon henanense via caspase activation. In the present study, we further investigated the role of calcium signaling in the Cd-induced apoptosis in the animals. Our data showed that Cd triggered gill cell apoptosis which is evidenced by apoptotic DNA fragmentation, activations of caspases-3, -8 and -9 and the presence of apoptotic morphological features. Moreover, Cd elevated the intracellular concentration of Ca²⁺, the protein concentration of calmodulin (CaM) and the activity of Ca²⁺-ATPase in the gill cells of the crabs. Pretreatment of the animals with ethylene glycol-bis-(b-aminoethyl ether)-N,N,N’,N’-tetraacetic acid (EGTA), Ca²⁺ chelator, inhibited Cd-induced activation of caspases-3, -8 and -9 as well as blocked the Cd-triggered apoptotic DNA fragmentation. The apoptotic morphological features were no longer observed in gill cells pretreated with the Ca²⁺ signaling inhibitors before Cd treatment. Our results indicate that Cd evokes gill cell apoptosis through activating Ca²⁺-CaM signaling transduction pathway.

Gene Expression Profiles of Main Olfactory Epithelium in Adenylyl Cyclase 3 Knockout Mice

Adenylyl Cyclase 3 (AC3) plays an important role in the olfactory sensation-signaling pathway in mice. AC3 deficiency leads to defects in olfaction. However, it is still unknown whether AC3 deficiency affects gene expression or olfactory signal transduction pathways within the main olfactory epithelium (MOE). In this study, gene microarrays were used to screen differentially expressed genes in MOE from AC3 knockout (AC3^−/−) and wild-type (AC3^+/+) mice. The differentially expressed genes identified were subjected to bioinformatic analysis and verified by qRT-PCR. Gene expression in the MOE from AC3^−/− mice was significantly altered, compared to AC3^+/+ mice. Of the 41266 gene probes, 3379 had greater than 2-fold fold change in expression levels between AC3^−/− and AC3^+/+ mice, accounting for 8% of the total gene probes. Of these genes, 1391 were up regulated, and 1988 were down regulated, including 425 olfactory receptor genes, 99 genes that are specifically expressed in the immature olfactory neurons, 305 genes that are specifically expressed in the mature olfactory neurons, and 155 genes that are involved in epigenetic regulation. Quantitative RT-PCR verification of the differentially expressed epigenetic regulation related genes, olfactory receptors, ion transporter related genes, neuron development and differentiation related genes, lipid metabolism and membrane protein transport etc. related genes showed that P75NTR, Hinfp, Gadd45b, and Tet3 were significantly up-regulated, while Olfr370, Olfr1414, Olfr1208, Golf, Faim2, Tsg101, Mapk10, Actl6b, H2BE, ATF5, Kirrrel2, OMP, Drd2etc. were significantly down-regulated. In summary, AC3 may play a role in proximal olfactory signaling and play a role in the regulation of differentially expressed genes in mouse MOE.

Serum containing Tongqiaohuoxue decoction suppresses glutamate-induced PC12 cell injury

Glutamate application is an established method of inducing PC12 cell injury. PC12 cells were cultured with serum containing Tongqiaohuoxue decoction consisting of moschus, Carthamus tinctorius, Rhizoma chuanxiong, Semen pruni persicae, and Radix Paeoniae Rubra. After 24 hours of co-cultivation, glutamate (12.5 mM) was added to the culture medium. We found that serum containing Tongqiaohuoxue decoction prevented the increase in reactive oxygen species, and the decreases in superoxide dismutase and Na⁺-K⁺-ATPase activity, induced by glutamate. It also reduced the concentration of malondialdehyde, enhanced the mitochondrial transmembrane potential, inhibited the elevation of cellular calcium, and decreased phosphorylation of calmodulin-dependent protein kinase II. Thus, serum containing Tongqiaohuoxue decoction had protective effects on cell proliferation and membrane permeability in glutamate-injured PC12 cells.

Intracellular translocation of histone deacetylase 5 regulates neuronal cell apoptosis

Histone deacetylase 5 (HDAC5) undergoes signal-dependent shuttling between the nucleus and cytoplasm, which is regulated in part by calcium/calmodulin-dependent kinase (CaMK)-mediated phosphorylation. Here, we report that HDAC5 regulates the survival of cortical neurons in pathological conditions. HDAC5 was evenly localized to the nucleus and cytoplasm in cultured cortical neurons. However, in response to 50μM NMDA conditions that induced neuronal cell apoptosis, nuclear-distributed HDAC5 was rapidly phosphorylated and translocated into cytoplasm of the cultured cortical neurons. Treatment with a CaMKII inhibitor KN93 suppressed HDAC5 phosphorylation and nuclear translocation induced by NMDA, whereas constitutively active CaMKIIα (T286D) stimulated HDAC5 nuclear export. Importantly, we showed that ectopic expression of nuclear-localized HDAC5 in cortical neurons suppressed NMDA-induced apoptosis. Finally, inactivation of HDAC5 by treatment with the class II-specific HDAC inhibitor trichostatin A (TSA) promoted NMDA-induced neuronal cell apoptosis. Altogether, these data identify HDAC5 and its intracellular translocation as key effectors of multiple pathways that regulate neuronal cell apoptosis.

Poly (ADP‑ribose) polymerase‑ and cytochrome c‑mediated apoptosis induces hepatocyte injury in a rat model of hyperammonia‑induced hepatic failure

Hepatic failure (HF) is caused by several factors, which induce liver cell damage and dysfunction. However, the specific mechanism of HF remains to be fully elucidated. The present study aimed to investigate the underlying cause of hepatocyte injury and liver dysfunction. Liver cells were isolated from healthy female Sprague-Dawley rats, aged between 6 and 8 weeks, weighing ~230 g. The liver cells were cultured in RPMI-1640 medium containing 10% fetal bovine serum. An MTT assay was used to examine the inhibitory rate of liver growth in each group. Flow cytometric analysis was performed to detect liver cells undergoing apoptosis. The protein expression levels of poly (ADP-ribose) polymerase (PARP) and cytochrome c (Cyt C) were detected by western blotting. The level of calmodulin-dependent kinase (CaMK) was assessed using an ELISA. The results indicated that the growth inhibitory rate of rat liver cells was significantly increased following treatment with increasing concentrations of NH₄Cl. The results of flow cytometric analysis demonstrated that the apoptotic rate in the BAPTA-acetoxymethyl ester group was significantly lower compared with the NH₄Cl group (P<0.05). Treatment with NH₄Cl increased the protein expression levels of PARP and Cyt C in the liver cells. The mRNA expression of CaMK decreased gradually following treatment with increasing concentrations of NH₄Cl for 6, 12 and 24 h. The results suggested that hepatocyte injury and liver dysfunction may be caused by inducing apoptosis via the PARP and Cyt C pathways. Additionally, downregulation of CaMK may be associated with the apoptosis observed in hepatocyte injury.

The Ca²⁺-calmodulin-Ca²⁺/calmodulin-dependent protein kinase II signaling pathway is involved in oxidative stress-induced mitochondrial permeability transition and apoptosis in isolated rat hepatocytes

Oxidative stress (OS) is a common event in most hepatopathies, leading to mitochondrial permeability transition pore (MPTP) formation and further exacerbation of both OS from mitochondrial origin and cell death. Intracellular Ca²⁺ increase plays a permissive role in these events, but the underlying mechanisms are poorly known. We examined in primary cultured rat hepatocytes whether the Ca²⁺/calmodulin (CaM)-dependent protein kinase II (CaMKII) signaling pathway is involved in this process, by using tert-butyl hydroperoxide (tBOOH) as a pro-oxidant, model compound. tBOOH (500 μM, 15 min) induced MPTP formation, as assessed by measuring mitochondrial membrane depolarization as a surrogate marker, and increased lipid peroxidation in a cyclosporin A (CsA)-sensitive manner, revealing the involvement of MPTPs in tBOOH-induced radical oxygen species (ROS) formation. Intracellular Ca²⁺ sequestration with BAPTA/AM, CaM blockage with W7 or trifluoperazine, and CaMKII inhibition with KN-62 all fully prevented tBOOH-induced MPTP opening and reduced tBOOH-induced lipid peroxidation to a similar extent to CsA, suggesting that Ca²⁺/CaM/CaMKII signaling pathway fully mediates MPTP-mediated mitochondrial ROS generation. tBOOH-induced apoptosis, as shown by flow cytometry of annexin V/propidium iodide, mitochondrial release of cytochrome c, activation of caspase-3 and increase in the Bax-to-Bcl-xL ratio, and the Ca²⁺/CaM/CaMKII signaling antagonists fully prevented these effects. Intramitochondrial CaM and CaMKII were partially involved in tBOOH-induced MPTP formation, since W7 and KN-62 both attenuated the tBOOH-induced, MPTP-mediated swelling of isolated mitochondria. We concluded that Ca²⁺/CaM/CaMKII signaling pathway is a key mediator of OS-induced MPTP formation and the subsequent exacerbation of OS from mitochondrial origin and apoptotic cell death.

Interplay of calcium and cadmium in mediating cadmium toxicity

The environmentally important toxic metal, cadmium, exists as the Cd(2+) ion in biological systems, and in this state structurally resembles Ca(2+). Thus, although cadmium exerts a broad range of adverse actions on cells by virtue of its propensity to bind to protein thiol groups, it is now well appreciated that Cd(2+) participates in a number of Ca(2+)-dependent pathways, attributable to its actions as a Ca(2+) mimetic, with a central role for calmodulin, and the Ca(2+)/calmodlin-dependent protein kinase II (CaMK-II) that mediates effects on cytoskeletal dynamics and apoptotic cell death. Cadmium interacts with receptors and ion channels on the cell surface, and with the intracellular estrogen receptor where it binds competitively to residues shared by Ca(2+). It increases cytosolic [Ca(2+)] through several mechanisms, but also decreases transcript levels of some Ca(2+)-transporter genes. It initiates mitochondrial apoptotic pathways, and activates calpains, contributing to mitochondria-independent apoptosis. However, the recent discovery of the role CaMK-II plays in Cd(2+)-induced cell death, and subsequent implication of CaMK-II in Cd(2+)-dependent alterations of cytoskeletal dynamics, has opened a new area of mechanistic cadmium toxicology that is a focus of this review. Calmodulin is necessary for induction of apoptosis by several agents, yet induction of apoptosis by Cd(2+) is prevented by CaMK-II block, and Ca(2+)-dependent phosphorylation of CaMK-II has been linked to increased Cd(2+)-dependent apoptosis. Calmodulin antagonism suppresses Cd(2+)-induced phosphorylation of Erk1/2 and the Akt survival pathway. The involvement of CaMK-II in the effects of Cd(2+) on cell morphology, and particularly the actin cytoskeleton, is profound, favouring actin depolymerization, disrupting focal adhesions, and directing phosphorylated FAK into a cellular membrane. CaMK-II is also implicated in effects of Cd(2+) on microtubules and cadherin junctions. A key question for future cadmium research is whether cytoskeletal disruption leads to apoptosis, or rather if apoptosis initiates cytoskeletal disruption in the context of Cd(2+).

BAFF activates Erk1/2 promoting cell proliferation and survival by Ca2+-CaMKII-dependent inhibition of PP2A in normal and neoplastic B-lymphoid cells

B-cell activating factor (BAFF) is involved in not only the physiology of normal B cells, but also the pathophysiology of aggressive B cells related to malignant and autoimmune diseases. However, how excessive BAFF promotes aggressive B-cell proliferation and survival is not well understood. Here we show that excessive human soluble BAFF (hsBAFF) enhanced cell proliferation and survival in normal and B-lymphoid (Raji) cells, which was associated with suppression of PP2A, resulting in activation of Erk1/2. This is supported by the findings that pretreatment with U0126 or PD98059, expression of dominant negative MKK1, or overexpression of PP2A prevented hsBAFF-induced activation of Erk1/2 and cell proliferation/viability in the cells. It appears that hsBAFF-mediated PP2A-Erk1/2 pathway and B-cell proliferation/viability was Ca(2+)-dependent, as pretreatment with BAPTA/AM, EGTA or 2-APB significantly attenuated these events. Furthermore, we found that inhibiting CaMKII with KN93 or silencing CaMKII also attenuated hsBAFF-mediated PP2A-Erk1/2 signaling and B-cell proliferation/viability. The results indicate that BAFF activates Erk1/2, in part through Ca(2+)-CaMKII-dependent inhibition of PP2A, increasing cell proliferation/viability in normal and neoplastic B-lymphoid cells. Our data suggest that inhibitors of CaMKII and Erk1/2, activator of PP2A or manipulation of intracellular Ca(2+) may be exploited for prevention of excessive BAFF-induced aggressive B-cell malignancies and autoimmune diseases.

Effects of cadmium on the actin cytoskeleton in renal mesangial cells

We provide an overview of our studies on cadmium and the actin cytoskeleton in mesangial cells, from earlier work on the effects of Cd2+ on actin polymerization in vivo and in vitro, to a role of disruption or stabilization of the cytoskeleton in apoptosis and apoptosis-like death. More recent studies implicate cadmium-dependent association of gelsolin and the Ca2+/calmodulin-dependent protein kinase II (CaMK-II) with actin filaments in cytoskeletal effects. We also present previously unpublished data concerning cadmium and the disruption of focal adhesions. The work encompasses studies on rat, mouse, and human mesangial cells. The major conclusions are that Cd2+ acts independently of direct effects on cellular Ca2+ levels to nevertheless activate Ca2+-dependent proteins that shift the actin polymerization–depolymerization in favour of depolymerization. Cadmium-dependent translocation of CaMK-IIδ, gelsolin, and a 50 kDa gelsolin cleavage fragment to the filamentous (F-)actin cytoskeleton appear to be involved. An intact filamentous actin cytoskeleton is required to initiate apoptotic and apoptotic-like death, but F-actin depolymerization is an eventual result.

Cadmium induces hydrogen peroxide production and initiates hydrogen peroxide-dependent apoptosis in the gill of freshwater crab, Sinopotamon henanense

Cadmium (Cd) is a well-known toxic heavy metal that accumulates in the aquatic environment. Cd has been reported to induce oxidative damage and apoptosis. We investigated the regulation mechanism of hydrogen peroxide (H(2)O(2)) on Cd-induced apoptosis. We show that in the gills of the freshwater crab Sinopotamon henanense Cd induced apoptosis, in a time- and concentration-dependent manner, as confirmed by DNA fragmentation analysis and transmission electron microscopy. Additionally, Cd caused production of H(2)O(2) after 2 h of treatment at 58 mg L(-1) Cd, and significantly increased the caspase-3/8/9 activity in crabs relative to the control group. Pre-treatment with the scavenger for H(2)O(2), dimethylthiourea (DMTU) and antioxidant, N-acetyl cysteine (NAC), effectively inhibited the activities of caspase-3 and caspase-9, eventually blocked Cd-induced DNA fragmentation and the appearance of markers for apoptotic cell death. These results suggest that Cd might induce intracellular H(2)O(2) generation to trigger the crab apoptotic processes by regulating the activities of caspase enzymes.

PCV2 induces apoptosis and modulates calcium homeostasis in piglet lymphocytes in vitro

This study investigated the process of PCV2-induced apoptosis and the effect of PCV2 inoculation on calcium homeostasis in piglet lymphocytes in vitro. PCV2-inoculated lymphocytes exhibited chromatin condensation, chromatin segregation, the appearance of membrane-enclosed apoptotic bodies, and DNA fragmentation. Moreover, the proportion of apoptotic cells increased significantly in PCV2-inoculated lymphocytes compared with controls. These results demonstrate that PCV2 induces lymphocyte apoptosis. Some evidence suggests that an alteration in the intracellular free Ca2+ concentration ([Ca2+]i) could cause apoptosis. We measured elevated [Ca2+]i in PCV2-inoculated lymphocytes for 12 or 24 h compared with controls. Our results support that PCV2-induced apoptosis may be relative to [Ca2+]i. In addition, calmodulin (CaM) was increased in PCV2-inoculated lymphocytes for 12 h compared with controls. The amount of CaM-dependent protein kinase II (CaMKII) did not change with PCV2 inoculation. We infer that the increased [Ca2+]i can bind CaM protein, but functions independently of CaMKII. Inositol 1,4,5-trisphosphate receptor (IP3R)-1 mRNA expression increased with PCV2 inoculation, whereas plasma Ca2+-ATP4 mRNA expression decreased. A decreased Ca2+-ATP4 level may inhibit Ca2+ efflux, and the increased IP3R-1 may trigger Ca2+ release from the endoplasmic reticulum. Both of these changes may contribute to increased [Ca2+]i.

CaMKII is involved in cadmium activation of MAPK and mTOR pathways leading to neuronal cell death

Cadmium (Cd), a toxic environmental contaminant, induces neurodegenerative diseases. Recently, we have shown that Cd elevates intracellular free calcium ion ([Ca(2+) ](i) ) level, leading to neuronal apoptosis partly by activating mitogen-activated protein kinases (MAPK) and mammalian target of rapamycin (mTOR) pathways. However, the underlying mechanism remains to be elucidated. In this study, we show that the effects of Cd-elevated [Ca(2+) ](i) on MAPK and mTOR network as well as neuronal cell death are through stimulating phosphorylation of calcium/calmodulin-dependent protein kinase II (CaMKII). This is supported by the findings that chelating intracellular Ca(2+) with 1,2-bis(o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl) ester or preventing Cd-induced [Ca(2+) ](i) elevation using 2-aminoethoxydiphenyl borate blocked Cd activation of CaMKII. Inhibiting CaMKII with KN93 or silencing CaMKII attenuated Cd activation of MAPK/mTOR pathways and cell death. Furthermore, inhibitors of mTOR (rapamycin), c-Jun N-terminal kinase (SP600125) and extracellular signal-regulated kinase 1/2 (U0126), but not of p38 (PD169316), prevented Cd-induced neuronal cell death in part through inhibition of [Ca(2+) ](i) elevation and CaMKII phosphorylation. The results indicate that Cd activates MAPK/mTOR network triggering neuronal cell death, by stimulating CaMKII. Our findings underscore a central role of CaMKII in the neurotoxicology of Cd, and suggest that manipulation of intracellular Ca(2+) level or CaMKII activity may be exploited for prevention of Cd-induced neurodegenerative disorders.

New insights into the Ca2+-ATPases that contribute to cadmium tolerance in yeast

Cadmium (Cd(2+)) is a toxic heavy metal which triggers several toxic effects in eukaryotes, including neurotoxicity and impaired calcium metabolism. In the model organism Saccharomyces cerevisiae, the best characterized pathway for Cd(2+) detoxification involves conjugation with glutathione (GSH) and subsequent transport to vacuoles by Ycf1p, an ATPase homologous to human MRP1 (Multidrug resistance associated protein 1). However, Cd(2+) tolerance also can be mediated by Pmr1p, a Ca(2+) pump located in the Golgi membrane, possibly through to the secretory pathway. Herein, we showed that inactivation of the PMR1 gene, alone or simultaneously with YCF1, delayed initial Cd(2+) capture compared to wild-type (WT) cells. In addition, Cd(2+) treatment altered the expression profile of yeast internal Ca(2+) transporters; specifically, PMC1 gene expression is induced substantially by the metal in WT cells, and this induction is stronger in mutants lacking YCF1. Taken together, these results indicate that, in addition to Pmr1p, the vacuolar Ca(2+)-ATPase Pmc1p also helps yeast cells cope with Cd(2+) toxicity. We propose a model where Pmc1p and Pmr1p Ca(2+)-ATPase function in cooperation with Ycf1p to promote Cd(2+) detoxification.