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

Prospective role of lusianthridin in attenuating cadmium-induced functional and cellular damage in rat thyroid

The thyroid represents the most prevalent form of head and neck and endocrine cancer. The present investigation demonstrates the anticancer effects of Lusianthridin against cadmium (Cd)-induced thyroid cancer in rats. Swiss Wistar rats were utilized in this experimental study. Cd was employed to induce thyroid cancer, and the rats were divided into different groups, receiving oral administration of Lusianthridin (20 mg/kg) for 14 days. Thyroid parameters, deiodinase levels, hepatic parameters, lipid parameters, and antioxidant parameters were respectively estimated. The mRNA expression was assessed using real-time reverse transcriptase polymerase chain reaction (RT-PCR). Lusianthridin significantly (P < 0.001) improved protein levels, T4, T3, free iodine in urine, and suppressed the level of TSH. Lusianthridin significantly (P < 0.001) enhanced the levels of FT3, FT4, and decreased the level of rT3. Lusianthridin significantly (P < 0.001) reduced the levels of D1, D2, D3, and enhanced the levels of hepatic parameters like AST, ALT. Lusianthridin remarkably (P < 0.001) altered the levels of lipid parameters such as LDL, total cholesterol, HDL, and triglycerides; antioxidant parameters viz., MDA, GSH, CAT, and SOD. Lusianthridin significantly altered the mRNA expression of Bcl-2, Bax, MEK1, ERK1, ERK2, p-eIf2α, GRP78, eIf2α, and GRP94. The results clearly state that Lusianthridin exhibits protective effects against thyroid cancer.

Ca2+/Calmodulin-Dependent Protein Kinase II Disrupts the Voltage Dependency of the Voltage-Dependent Anion Channel on the Lipid Bilayer Membrane

Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) is a key enzyme that plays a significant role in intracellular signaling and the modulation of mitochondrial membrane properties. It is known that the voltage-dependent anion channel (VDAC) is one of the most abundant outer mitochondrial membrane (OMM) proteins acting as a significant passageway and regulatory site for various enzymes, proteins, ions, and metabolites. Considering this, we hypothesize that VDAC could be one of the targets for CaMKII enzymatic activity. Our in vitro experiments indicate that VDAC can be phosphorylated by the CaMKII enzyme. Moreover, the bilayer electrophysiology experimental data indicate that CaMKII significantly reduces VDAC's single-channel conductivity; its open probability remains high at all the applied potentials between +60 and -60 mV, and the voltage dependency was lost, which suggests that CaMKII disrupted the VDAC's single-channel activities. Hence, we can infer that VDAC interacts with CaMKII and thus acts as a vital target for its activity. Furthermore, our findings suggest that CaMKII could play a significant role during the transport of ions and metabolites across the outer mitochondrial membrane (OMM) through VDAC and thus regulate apoptotic events.

Host A-to-I RNA editing signatures in intracellular bacterial and single-strand RNA viral infections

Background

Microbial infection is accompanied by remodeling of the host transcriptome. Involvement of A-to-I RNA editing has been reported during viral infection but remains to be elucidated during intracellular bacterial infections.

Results

Herein we analyzed A-to-I RNA editing during intracellular bacterial infections based on 18 RNA-Seq datasets of 210 mouse samples involving 7 tissue types and 8 intracellular bacterial pathogens (IBPs), and identified a consensus signature of RNA editing for IBP infections, mainly involving neutrophil-mediated innate immunity and lipid metabolism. Further comparison of host RNA editing patterns revealed remarkable similarities between pneumonia caused by IBPs and single-strand RNA (ssRNA) viruses, such as altered editing enzyme expression, editing site numbers, and levels. In addition, functional enrichment analysis of genes with RNA editing highlighted that the Rab GTPase family played a common and vital role in the host immune response to IBP and ssRNA viral infections, which was indicated by the consistent up-regulated RNA editing of Ras-related protein Rab27a. Nevertheless, dramatic differences between IBP and viral infections were also observed, and clearly distinguished the two types of intracellular infections.

Conclusion

Our study showed transcriptome-wide host A-to-I RNA editing alteration during IBP and ssRNA viral infections. By identifying and comparing consensus signatures of host A-to-I RNA editing, our analysis implicates the importance of host A-to-I RNA editing during these infections and provides new insights into the diagnosis and treatment of infectious diseases.

The endo-beta mannase MAN7 contributes to cadmium tolerance by modulating root cell wall binding capacity in Arabidopsis thaliana

The heavy metal cadmium (Cd) is detrimental to crop growth and threatens human health through the food chain. To cope with Cd toxicity, plants employ multiple strategies to decrease Cd uptake and its root-to-shoot translocation. However, genes that participate in the Cd-induced transcriptional regulatory network, including those encoding transcription factors, remain largely unidentified. In this study, we demonstrate that ENDO-BETA-MANNASE 7 (MAN7) is necessary for the response of Arabidopsis thaliana to toxic Cd levels. We show that MAN7 is responsible for mannase activity and modulates mannose content in the cell wall, which plays a role in Cd compartmentalization in the cell wall under Cd toxicity conditions. Additionally, the repression of root growth by Cd was partially reversed via exogenous application of mannose, suggesting that MAN7-mediated cell wall Cd redistribution depends on the mannose pathway. Notably, we identified a basic leucine zipper (bZIP) transcription factor, bZIP44, that acts upstream of MAN7 in response to Cd toxicity. Transient dual-luciferase assays indicated that bZIP44 directly binds to the MAN7 promoter region and activates its transcription. Loss of bZIP44 function was associated with greater sensitivity to Cd treatment and higher accumulation of the heavy metal in roots and shoots. Moreover, MAN7 overexpression relieved the inhibition of root elongation seen in the bzip44 mutant under Cd toxicity conditions. This study thus reveals a pathway showing that MAN7-associated Cd tolerance in Arabidopsis is controlled by bZIP44 upon Cd exposure.

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.

Low levels of cadmium exposure affect bone by inhibiting Lgr4 expression in osteoblasts and osteoclasts

BACKGROUND

Cadmium exposure is associated with bone loss. However, the mechanisms involved have not yet been fully understood. Leucine-rich repeat containing GPCR-4 (LGR4) can bind with the receptor activator of nuclear factors κB ligand (RANKL) and inhibit osteoclast formation. In addition, Lgr4 plays an important role in maintaining osteoblast activity. In the present study the effect of cadmium exposure on bone was investigated in terms of Lgr4 expression.

METHODS

Raw 264.7 cells and primary osteoblasts were exposed to cadmium (0-60 nM/L). The effects of cadmium on osteoclast formation and osteoblast activity were investigated. Osteoclast differentiation-related (Traf6, NFATc1) and osteoblast-related (RANKL; osteoprotegerin, OPG) gene and protein expression were determined. Lgr4 expression in osteoclasts and osteoblasts were also determined. A rat model was established to show the effects of cadmium (50 mg/L) on bone loss and Lgr4 expression in vivo.

RESULTS

Cadmium exposure inhibited osteoblast activities and stimulated osteoclast formation. Cadmium exposure also inhibited Lgr4 expression in both osteoclasts and osteoblasts. Low dose of RANKL added to the culture medium could promote osteoclast formation in cadmium-pretreated RAW264.7 cells. Blocking Lgr4 in osteoclasts only slightly inhibited cadmium-induced osteoclast formation in cadmium-pretreated RAW264.7 cells. Cadmium significantly upregulated the AKT/ERK signaling pathway. An in vivo study showed that cadmium exposure promoted osteoclast formation and inhibited Lgr4 expression.

CONCLUSIONS

Our data indicates that cadmium may induce bone loss by inhibiting Lgr4-related bone formation and promoting Lgr4-related osteoclast formation.

Calmodulin Modulates the Gating Properties of Voltage-Dependent Anion Channel from Rat Brain Mitochondria

Calmodulin (CaM) is a key signaling protein that plays a decisive role in mitochondrial Ca2+ homeostasis and signaling and modulates the mitochondrial membrane properties. We propose that voltage-dependent anion channel 1 (VDAC1), one of the most abundant outer mitochondrial membrane (OMM) proteins, could be its possible target or site of action. VDAC1 is known to play a crucial role in the mitochondrial Ca2+ signaling mechanism. Bilayer electrophysiology experiments show that CaM significantly reduces VDAC1's conductivity and modulates its gating as well as permeability properties. Also, spectrofluorimetric analysis indicates the possibility of binding CaM with VDAC1. Theoretical analysis of fluorescence data shows that the aforementioned protein-protein interaction is not linear, but rather it is a complex nonlinear process. In VDAC1, CaM binding site has been predicted using various bioinformatics tools. It is proposed that CaM could interact with VDAC1's outer-loop region and regulate its gating properties. Our findings suggest that VDAC1-CaM interaction could play a crucial role in the transport of ions and metabolites through the OMM and the regulation of the mitochondrial Ca2+ signaling mechanism through alteration of VDAC1's gating and conductive properties.

Pumilio RNA Binding Family Member 2 Promotes the Proliferation and Metastasis of Lung Cancer Cells by Regulating Ca2+ Signaling Pathway via Targeting C-X-C Chemokine Receptor Type 4

The aim of the present study was to investigate the mechanism by which pumilio RNA binding family member 2 (PUM2), an RNA-binding protein (RBP) of C-X-C chemokine receptor type 4 (CXCR4), exerts its effects on the development of lung cancer. RT-qPCR and western blot analysis were utilized to measure the expression of PUM2 in several lung cancer cell lines. Cell Counting Kit-8 (CCK-8), colony formation assay, transwell- and wound healing assays were employed to determine the proliferation, invasion and migration of NCI-H520 cells, respectively. Next, the expression of CXCR4 was measured using western blot analysis, and the combination between PUM2 and CXCR4 was verified by RNA immunoprecipitation (RIP) assay and RNA pull down assay. Finally, whether the expression of PUM2 can affect the Ca2+ signaling pathway was confirmed by western blot assay. Results revealed that the expression level of PUM2 was notably upregulated in lung cancer cells, and knockdown of PUM2 significantly inhibited the proliferation, invasion and migration of NCI-H520 cells. PUM2 was confirmed to be the RBP of CXCR4, and PUM2 knockdown decreased the expression of CXCR4. In addition, PUM2 silencing inhibited the phosphorylation of CaMKII, ERK, and MEK. Taken together, these findings demonstrated that PUM2 could promote the proliferation and metastasis of lung cancer cells by regulating Ca2+ signaling pathway via targeting CXCR4, which may provide a novel insight for the future treatment of lung cancer.

DNA methylation and gene expression alterations in zebrafish embryos exposed to cadmium

An unexplored attributing molecular mechanism of Cd toxicity is interference with the epigenetic machinery, such as DNA methylation, processes that are crucial for early fetal development. In order to investigate the effects of Cd on the expression of metallothionein (MT) and Dnmts transcripts, markers of DNA methylation, and signaling pathway gene expression, zebrafish embryos were exposed during 24 hours post-fertilization (starting at maximum 8-cell stage) to 0.0089, 0.089, and 0.89 μM Cd. The results showed that the Cd accumulation in zebrafish embryo reached a stable level after 12 hpf, and the Cd accumulation at individual time points was significantly different among different concentration groups. MT mRNA fold was significantly positive with the Cd content in embryos. We observed that the expression level of DNA methyltransferase (Dnmts) in the 0.089 μM Cd exposure group was significantly up-regulated. Dnmt1 expression was significantly up-regulated in the 0.89 μM Cd exposure group, and Dnmt3s expression and global methylation levels were significantly down-regulated. Cd up-regulated ErbB-3 gene expression, down-regulated ErbB-4 gene expression, and neutralized ErbB-1 gene expression. Cd activated Ca2+, MAPK-JUK, p38 MAP kinase, PI3K-AKT, and VEGF signaling pathway genes, indicating these pathway genes related to Cd exposure level. The results are helpful to clarify the molecular mechanism of DNA methylation in zebrafish embryo under metal pressure and further interference with the epigenetic machinery.

Resveratrol protects MC3T3-E1 cells against cadmium-induced suppression of osteogenic differentiation by modulating the ERK1/2 and JNK pathways

Resveratrol (RES) is a natural polyphenolic compound with a broad range of physiological and pharmacological properties. Previous studies have shown that RES also plays an important role in protecting and promoting early bone metabolism and differentiation. The accumulation of cadmium (Cd), one of the world's most poisonous substances, can inhibit skeletal growth and bone maturation, thus causing osteoporosis. However, whether RES can prevent the Cd-induced inhibition of osteogenic differentiation remains unknown. In this study, we found that RES promoted the early maturity of osteoblastic MC3T3-E1 cells, as demonstrated by the significantly increased mRNA and protein expression of a range of differentiation markers, including alkaline phosphatase (ALP), collagen 1 (COL1), bone morphogenetic protein-2 (BMP-2), and runt-related transcription factor 2 (RUNX2). In contrast, we found that cadmium chloride (CdCl₂) inhibited the viability and osteogenic maturity of MC3T3-E1 cells. We also demonstrated that RES pretreatment for 30 min provided significant protection against Cd-induced apoptosis and attenuated the inhibition of osteogenic differentiation induced by Cd by modulating ERK1/2 and JNK signaling. In conclusion, our results indicate that RES is a potential femoral protectant that not only enhance the viability and early differentiation of osteoblasts, but also protect osteoblasts from cadmium damage.

Isoflurane triggers the acute cognitive impairment of aged rats by damaging hippocampal neurons via the NR2B/CaMKII/CREB pathway

Isoflurane was responsible for acute neuronal impairment, but its potential molecular mechanisms in damaging hippocampal neurons had not been clearly understood. This study aimed to explore the underlying mechanism of how isoflurane affected the cognitive function of aged rats by damaging the hippocampal neurons. Acute cognitive impairment was found in aged Wistar rats via Morris water maze test and Y-maze test after isoflurane anesthesia in a dose-dependent manner compared with the control group in vivo. Isoflurane also decreased the viabilities and strengthened the apoptotic potential of hippocampal neurons by damaging the mitochondria in a time-dependent manner compared with the control group which was reported by MTT, immunofluorescent assay, flow cytometry and western blot assay in vitro. Isoflurane jeopardized hippocampal neurons by directly inactivating the NR2B/CaMKII/CREB pathway and its harmful effects could be ameliorated by adding CaMKII activator CdCl₂. These findings provided evidence that the cognitive ability of aged rats was injured by isoflurane exposure and isoflurane also inhibited the viability and enhanced the apoptosis of hippocampal neurons by damaging the mitochondria through inhibition of the NR2B/CaMKII/CREB pathway and its harmful roles could be partially ameliorated by CdCl₂. Our study demonstrated that isoflurane could cause acute neuronal damage and we provided fresh insights that contributed to the safe use of anesthetic agents and the prevention of PND in elderly people.

Antagonistic effect of VDR/CREB1 pathway on cadmium-induced apoptosis in porcine spleen

Cadmium (Cd) is a toxic trace element that can enter the environment with industrial waste and accumulate in the body but the health effects of Cd on ternary pigs are still lacking in research. In order to explore the effect of Cd on the apoptosis of pig spleen and its mechanism, this study chose ternary pig as the research object to detect relevant indicators in pig spleen under Cd exposure. The results of this study showed that Cd exposure can induce apoptosis by promoting the absorption of various toxic trace elements in the spleen and inducing oxidative stress. We also found that the mechanism of Cd-induced apoptosis is closely related to the VDR/CREB1 pathway. On the one hand, Cd exposure can activate VDR, and indirectly regulate the CYP family, affecting the normal function of the spleen. On the other hand, VDR and its downstream genes antagonize the toxicity of Cd by maintaining the stability of the mitochondrial-related endoplasmic reticulum membrane structure. Our research will help researchers to further understand the physiological toxicity of Cd.

Metabolic signatures for safety assessment of low-level cadmium exposure on human osteoblast-like cells

Cadmium has been widely detected in the environment and various foods. The association between cadmium burden and osteoporosis has been studied in cohorts. However, the effects and mechanisms of environmental cadmium exposure on bone metabolism is poorly understood. This study aims to investigate the altered metabolites in bone cells affected by low-level cadmium by metabolomics analysis. Specifically, we used the dosage of cadmium that do not decrease the cell viability (determined by MTT assay) to treat Saos-2 cells for 24 h. ICP-MS was applied to quantify the cadmium in culture medium and cell precipitate. The cellular metabolites were extracted and analyzed by liquid chromatography-mass spectrometry. The pathway analysis based on the identified differential metabolites showed that 1 μM cadmium significantly affected citric acid cycle and malate-aspartate shuttle, while 10 μM cadmium treatment affected citric acid cycle, alanine metabolism, glucose-alanine cycle, pyrimidine metabolism and glutamate metabolism. Taken together, 1 μM cadmium exposure could suppress the electrons transportation from the cytosol to mitochondrial matrix in Saos-2, and the impediment of the electron transport chain further inhibited downstream activities in citric acid cycle, which resulted in the accumulation of pyruvic acid. In addition, the suppressed pyrimidine degradation resulted in senescent nucleic acid accumulation and the decrease of mRNA transcription in Saos-2 cells. In general, our studies unveil the cadmium-induced metabolic perturbations in Saos-2 cells and demonstrate the feasibility of our established metabolomics pipeline to understand cadmium-induced effects on bone.

The protective effects of simvastatin in Cadmium-Induced preosteoblast injury through Nox4

Cadmium (Cd) has a direct toxic effect on bones. Statins such as simvastatin have protective effects on various diseases, including on tissue injury. The current study revealed the efficacy of simvastatin on Cd-induced preosteoblast injury. Preosteoblast MC3T3-E1 cells were incubated with various doses of CdCl₂ for 12 h, 24 h and 48 h, and then the cell cytotoxicity was assessed using MTT assay and flow cytometry, respectively. The expression level of Nox4 was assessed by Western blot and qRT-PCR. The morphological appearance of MC3T3-E1 cells was observed under a microscope. Cells exposed to CdCl₂ (5 µM) were further treated by simvastatin at various doses, subsequently cell viability, apoptosis and the expression of Nox4 were measured. Furthermore, to confirm the protective effects of simvastatin on Cd-induced pre-osteoblast injury, functional rescue assays were performed after corresponding cell treatment by simvastatin (10^-8 M), CdCl₂ (5 µM), and overexpression of Nox4. Expressions of cell apoptosis-related markers were measured by Western blot and qRT-PCR. The results revealed that CdCl₂ caused MC3T3-E1 cell injury because the cell viability was decreased and the apoptosis was increased. Nox4 expression was up-regulated with the increase of CdCl₂ concentrations. Simvastatin increased the cell viability, relieved the cell apoptosis and Nox4 expression previously increased by CdCl₂. The effects of CdCl₂ on MC3T3-E1 cells and Nox4 expression could be attenuated by simvastatin, and promoted by Nox4 overexpression. The current study found that simvastatin protects Cd-induced preosteoblast injury via Nox4, thus, it can be used as a potential drug for treating cadmium-induced bone injury.

Cadmium induces apoptosis via generating reactive oxygen species to activate mitochondrial p53 pathway in primary rat osteoblasts

Cadmium (Cd), a heavy metal produced by various industries, contaminates the environment and seriously damages the skeletal system of humans and animals. Recent studies have reported that Cd can affect the viability of cells, including osteoblasts, both in vivo and in vitro. However, the mechanism of Cd-induced apoptosis remains unclear. In the present study, primary rat osteoblasts were used to investigate the Cd-induced apoptotic mechanism. We found that treatment with 2 and 5 μM Cd for 12 h decreased osteoblast viability and increased apoptosis. Furthermore, Cd increased the generation of reactive oxygen species (ROS), and, thus, DNA damage measured via p-H2AX. The level of the nuclear transcription factor p53 was significantly increased, which upregulated the expression of PUMA, Noxa, Bax, and mitochondrial cytochrome c, downregulated the expression of Bcl-2, and increased the level of cleaved caspase-3. However, pretreatment with the ROS scavenger N-acetyl-l-cysteine (NAC) or the p53 transcription specific inhibitor PFT-α suppressed Cd-induced apoptosis. Our results indicate that Cd can induce apoptosis in osteoblasts by increasing the generation of ROS and activating the mitochondrial p53 signaling pathway, and this mechanism requires the transcriptional activation of p53.

Hybrid silica aerogel nanocomposite adsorbents designed for Cd(II) removal from aqueous solution

Hybrid silica aerogel (HSA) nanoparticles were synthesized by sol-gel method and drying at ambient pressure. Also, two magnetic nanocomposites of HSA with Fe₃ O₄ nanoparticles and chitosan (CS) were prepared including HSA-Fe₃ O₄ and HSA-Fe₃ O₄ -CS. The morphology, structure, and magnetic properties of the HSA as well as its nanocomposites were analyzed by SEM, XRD, TGA, VSM, and ATR-FTIR techniques. The saturation magnetization (M_s ) values for the Fe₃ O₄ NPs, HSA-Fe₃ O_4, and HSA-Fe₃ O₄ -CS nanocomposite film were 69.93, 19.04, and 5.77 emu/g, respectively. Furthermore, the abilities of the HSA, HSA-Fe₃ O₄ , CS, and HSA-Fe₃ O₄ -CS adsorbents were assessed for removal of cadmium(II) heavy metal ions (100 ppm) from aqueous solution. All adsorbents removed/adsorbed the maximum Cd(II) ions in 120 min when adsorbent dosage = 20 mg and pH = 8. Moreover, the highest adsorption capacities were 58.5, 69.4, 65.8, and 71.9 mg/g for the HSA, CS, HSA-Fe₃ O_4, and HSA-Fe₃ O₄ -CS, respectively. Kinetic studies using all adsorbents verified that Cd(II) adsorption obeyed the second-order model illustrating the analyte chemisorption was happened on the adsorbent surfaces. All adsorption data were well consistent with the Langmuir isotherms. The reusability experiment confirmed that all of adsorbents could preserve >95% of their initial adsorption capacities even after five series of adsorption/desorption tests. PRACTITIONER POINTS: Hybrid silica aerogel (HSA), HSA-Fe₃ O_4, and HSA-Fe₃ O₄ -CS adsorbents were produced. Nanocomposites were characterized by XRD, TGA, SEM, VSM, and ATR-FTIR analysis. Adsorption of cadmium(II) ions by adsorbents was examined in aqueous solution. The highest adsorption capacity was obtained for the HSA-Fe₃ O₄ -CS (71.9 mg/g). Cd(II) adsorption followed second-order kinetics and Langmuir isotherm model.

Cinnamon-flavored electronic cigarette liquids and aerosols induce oxidative stress in human osteoblast-like MG-63 cells

As noncombustible nicotine delivery devices, electronic cigarettes (e-cigarettes) are the most popular tobacco product among youth. The widespread popularity of e-cigarettes combined with possible health consequences suggest a need to further research health hazards associated with e-cigarette use. Since conventional tobacco use is a risk factor for osteoporosis, this study investigates the impact of nicotine-free, cinnamon-flavored e-cigarette liquid (e-liquid) on bone-forming osteoblasts compared to flavorless e-liquid. Human tumor-derived osteoblast-like MG-63 cells were exposed for 24 h or 48 h to 0.0.4 %, 0.04 %, 0.4 % or 1 % of unvaped e-liquid or 0.0025 %, 0.025 %, 0.25 %, 1 % or 2.5 % of aerosol condensate in addition to a culture medium only control. Changes in cell viability were assessed by MTT assay, and the expression of a key bone protein, collagen type I, was analyzed by immunofluorescence. Production of reactive oxygen species (ROS) was detected by fluorometry to assess oxidative stress. Cell viability decreased in a dose-dependent manner, and ROS production increased, which was most pronounced with cinnamon-flavored e-liquids. There were no detectable changes in collagen type I protein following exposure to any of the aerosol condensates. This study demonstrates osteoblast-like cells are sensitive to both e-liquids and aerosol condensates and suggests the cytotoxicity of cinnamon-flavored e-liquids might be associated with oxidative stress rather than changes in collagen type I protein expression. This in vitro study provides insight into the potential impacts of e-cigarette use on bone cells.

Propofol attenuates TNF-α-induced MMP-9 expression in human cerebral microvascular endothelial cells by inhibiting Ca2+/CAMK II/ERK/NF-κB signaling pathway

Metalloproteinase 9 (MMP-9) is able to degrade collagen IV, an important component of blood-brain barrier (BBB). Expression of MMPs, especially MMP-9, correlates with BBB disruption during central nervous system inflammation. Propofol has been reported to have anti-inflammation effects. In this study, we investigated the effects of propofol on TNF-α-induced MMP-9 expression in human cerebral microvascular endothelial cells (hCMEC/D3 cells) and explored the underlying mechanisms. The hCMEC/D3 cells were treated with propofol (25 μM), followed by TNF-α (25 ng/mL). We showed that TNF-α treatment markedly increased MMP-9 expression and decreased collagen IV expression in hCMEC/D3 cells, which was blocked by pretreatment with propofol. TNF-α-induced downregulation of collagen IV was also reversed by MMP-9 knockdown with siRNA. We revealed that TNF-α upregulated MMP-9 expression in hCMEC/D3 cells through activation of Ca²⁺/CAMK II/ERK/NF-κB signaling pathway; co-treatment with inhibitors of CaMK II (KN93), ERK (LY3214996), NF-κB (PDTC) or Ca²⁺chelator (BAPTA-AM) abrogated the effect of TNF-α on MMP-9 expression. We further established an in vitro BBB model by co-culturing of hCMEC/D3 cells and human astrocytes for 6 days and measuring trans-endothelial electrical resistance (TEER) to reflect the BBB permeability. TNF-α treatment markedly decreased TEER value, which was attenuated by pretreatment with propofol (25 μM) or MMP-9 knockdown with siRNA. In conclusion, propofol inhibits TNF-α-induced MMP-9 expression in hCMEC/D3 cells via repressing the Ca²⁺/CAMKII/ERK/NF-κB signaling pathway. TNF-α-impaired BBB integrity could be reversed by propofol, and propofol attenuates the inhibitory effect of TNF-α on collagen IV.

Effects of sub-chronic, low-dose cadmium exposure on kidney damage and potential mechanisms

Background

The present study was to investigate the potential mechanisms underlying the sub-chronic low-dose cadmium (Cd) exposure induced renal injury in rats.

Methods

Totally 40 male adult SD rats were randomly divided into four groups: control group, low-dose Cd group (1 mg/kg CdCl₂), moderate-dose Cd group (2.5 mg/kg) and high-dose Cd group (5 mg/kg).

Results

From the 3^rd week, the body weight of rats in moderate-dose and high-dose declined significantly as compared to the control group (P<0.05); the liver to body weight ratio increased, the volumes of 24-hour urine and drinking-water decreased markedly (P<0.05), the BUN, SCr and β₂-MG increased significantly, but the Fe²⁺ concentration decreased markedly as compared to the control group (P<0.05); the serum MDA and SOD₁ content contents increased, but the serum SOD₂ and CAT contents decreased significantly in Cd-treated groups (P<0.05); Renal injury deteriorated with the increase in Cd dose; swelling glomeruli showed stenotic renal-tubules, and epithelial-cell-necrosis, shedding and accumulation in the lumen, massive infiltrated inflammatory cells and interstitial hyperaemia were observed; The mitochondria in renal-tubular-epithelial-cells displayed swelling, deformation and vacuolation; the renal ROS content increased in Cd-exposure-groups; the renal SOD₁ expression increased but the expression of SOD₂ and CAT decreased (P<0.05). The Bcl-2 expression decreased, but Bax expression and Bax/Bcl-2 ratio increased significantly in a Cd-dose dependent manner.

Conclusions

Cd may cause renal injury in a dose dependent manner, which may be ascribed to the disordered Fe²⁺ absorption, redox imbalance and apoptosis in the kidney.

Anti-Osteogenic Activity of Cadmium in Zebrafish

Among the many anthropogenic chemicals that end up in the aquatic ecosystem, heavy metals, in particular cadmium, are hazardous compounds that have been shown to affect developmental, reproductive, hepatic, hematological, and immunological functions in teleost fish. There is also evidence that cadmium disturbs bone formation and skeletal development, but data is scarce. In this work, zebrafish was used to further characterize the anti-osteogenic/osteotoxic effects of cadmium and gain insights into underlying mechanisms. Upon exposure to cadmium, a reduction of the opercular bone growth was observed in 6-days post-fertilization (dpf) larvae and an increase in the incidence of skeletal deformities was evidenced in 20-dpf post-larvae. The extent and stiffness of newly formed bone was also affected in adult zebrafish exposed to cadmium while regenerating their caudal fin. A pathway reporter assay revealed a possible role of the MTF-1 and cAMP/PKA signaling pathways in mechanisms of cadmium osteotoxicity, while the expression of genes involved in osteoblast differentiation and matrix production was strongly reduced in cadmium-exposed post-larvae. This work not only confirmed cadmium anti-osteogenic activity and identified targeted pathways and genes, but it also suggested that cadmium may affect biomechanical properties of bone.

Electronic cigarette liquid exposure induces flavor-dependent osteotoxicity and increases expression of a key bone marker, collagen type I

Electronic cigarettes (e-cigarettes) are nicotine delivery devices advertised as a healthier alternative to conventional tobacco products, but their rapid rise in popularity outpaces research on potential health consequences. As conventional tobacco use is a risk factor for osteoporosis, this study examines whether exposure to electronic liquid (e-liquid) used in e-cigarettes affects bone-forming osteoblasts. Human MG-63 and Saos-2 osteoblast-like cells were treated for 48 hours with 0.004%-4.0% dilutions of commercially available e-liquids of various flavors with or without nicotine. Changes in cell viability and key osteoblast markers, runt-related transcription factor 2 and Col1a1, were assessed. With all e-liquids tested, cell viability decreased in a dose-dependent manner, which was least pronounced in flavorless e-liquids, most pronounced in cinnamon-flavored e-liquids and occurred independently of nicotine. Col1a1, but not runt-related transcription factor 2, mRNA expression was upregulated in response to coffee-flavored and fruit-flavored e-liquids. Cells treated with a non-cytotoxic concentration of fruit-flavored Mango Blast e-liquid with or without nicotine showed significantly increased collagen type I protein expression compared to culture medium only. We conclude that the degree of osteotoxicity is flavor-dependent and occurs independently of nicotine and that flavored e-liquids reveal collagen type I as a potential target in osteoblasts. This study elucidates potential consequences of e-cigarette use in bone.

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.

Biochemical and transcriptional analyses of cadmium-induced mitochondrial dysfunction and oxidative stress in human osteoblasts

Cadmium (Cd) accumulation is known to occur predominantly in kidney and liver; however, low-level long-term exposure to Cd may also result in bone damage. Few studies have addressed Cd-induced toxicity in osteoblasts, particularly upon cell mitochondrial energy processing and putative associations with oxidative stress in bone. To assess the influence of Cd treatment on mitochondrial function and oxidative status in osteoblast cells, human MG-63 cells were treated with Cd (up to 65 μM) for 24 or 48 h. Intracellular reactive oxygen species (ROS), lipid and protein oxidation and antioxidant defense mechanisms such as total antioxidant activity (TAA) and gene expression of antioxidant enzymes were analyzed. In addition, Cd-induced effects on mitochondrial function were assessed by analyzing the activity of enzymes involved in mitochondrial respiration, membrane potential (ΔΨm), mitochondrial morphology and adenylate energy charge. Treatment with Cd increased oxidative stress, concomitantly with lipid and protein oxidation. Real-time polymerase chain reaction (qRT-PCR) analyses of antioxidant genes catalase (CAT), glutathione peroxidase 1 (GPX1), glutathione S-reductase (GSR), and superoxide dismutase (SOD1 and SOD2) exhibited a trend toward decrease in transcripts in Cd-stressed cells, particularly a downregulation of GSR. Longer treatment with Cd (48 h) resulted in energy charge states significantly below those commonly observed in living cells. Mitochondrial function was affected by ΔΨm reduction. Inhibition of mitochondrial respiratory chain enzymes and citrate synthase also occurred following Cd treatment. In conclusion, Cd induced mitochondrial dysfunction which appeared to be associated with oxidative stress in human osteoblasts.

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.

Study on the influential biochemical indices of Cd(II) on Eisenia fetida in oxidative stress by principal component analysis in the natural soil

With the aggravation of heavy metal pollution in soil, the individual heavy metal content monitoring cannot predict the true effects of harmful substances on the ecosystems. Thus, the effective biological evaluation system should be established to assess the pollution risk caused by heavy metal. Earthworms are widely distributed in the soil, and at the bottom of the food chain, the changes of biochemical indices play an important role in the early warning for heavy metal pollution. Principal component analysis (PCA) is a statistical method that derives several independent principal components from the original variable based on retaining the information as much as possible. This paper is aimed at finding out and analyzing the key monitoring factors related to Cd²⁺ on the earthworm Eisenia fetida in oxidative stress. The Cd²⁺ stress concentrations were set at 0, 1, 10, 20, 100, 200, 400, and 800 mg kg^-1, and the post-clitellum segment of earthworm was chosen to determine TP, POD, SOD, GST, GPX, CAT, MDA, VE, and AChE. The results showed that the main bioindicators associated with oxidative stress reaction were GST, POD, and MDA at the exposure time of 10 days; at 20 days GPX, MDA, and AChE; at 30 days CAT, TP, and GPX; CAT, MDA, and SOD at 40th day. These results indicated that PCA can quickly, effectively, directly, and scientifically select biomarkers of oxidative stress induced by Cd and improve the accuracy and scientificity of earthworm as a biomarker in monitoring and early warning for heavy metal-contaminated soil.

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.

Fish as a model to assess chemical toxicity in bone

Environmental toxicology has been expanding as growing concerns on the impact of produced and released chemical compounds over the environment and human health are being demonstrated. Among the toxic effects observed in organisms exposed to pollutants, those affecting skeletal tissues (osteotoxicity) have been somehow overlooked in comparison to hepato-, immune-, neuro- and/or reproductive toxicities. Nevertheless, sub-lethal effects of toxicants on skeletal development and/or bone maintenance may result in impaired growth, reduced survival rate, increased disease susceptibility and diminished welfare. Osteotoxicity may occur by acute or chronic exposure to different environmental insults. Because of biologically and technically advantagous features - easy to breed and inexpensive to maintain, external and rapid rate of development, translucent larvae and the availability of molecular and genetic tools - the zebrafish (Danio rerio) has emerged in the last decade as a vertebrate model system of choice to evaluate osteotoxicity. Different experimental approaches in fish species and analytical tools have been applied, from in vitro to in vivo systems, from specific to high throughput methodologies. Current knowledge on osteotoxicity and underlying mechanisms gained using fish, with a special emphasis on zebrafish systems, is reviewed here. Osteotoxicants have been classified into four categories according to the pathway involved in the transduction of the osteotoxic effects: activation/inhibition of membrane and/or nuclear receptors, alteration of redox condition, mimicking of bone constituents and unknown pathways. Knowledge on these pathways is also reported here as it may provide critical insights into the development, production and release of future chemical compounds with none or low osteotoxicity, thus promoting the green/environmental friendly chemistry.