Cyclosporin A induces apoptosis in H9c2 cardiomyoblast cells through calcium-sensing receptor-mediated activation of the ERK MAPK and p38 MAPK pathways

Cardiovascular toxicities by calcineurin inhibitors: Cellular mechanisms behind clinical manifestations

Calcineurin inhibitors (CNI), including cyclosporine A (CsA) and tacrolimus (TAC), are cornerstones of immunosuppressive therapy in solid organ transplant recipients. While extensively recognized for their capacity to induce nephrotoxicity, hypertension, and dyslipidemia, emerging reports suggest potential direct cardiovascular toxicities associated with CNI. Evidence from both in vitro and in vivo studies has demonstrated direct cardiotoxic impact of CNI, manifesting itself as induction of cardiomyocyte apoptosis, enhanced oxidative stress, inflammatory cell infiltration, and cardiac fibrosis. CNI enhances cellular apoptosis through CaSR via activation of the p38 MAPK pathway and deactivation of the ERK pathway, and enhancement of miR-377 axis. Although CNI could attenuate cardiac hypertrophy in certain animal models, CNI concurrently impaired systolic function, enhanced cardiac fibrosis, and increased the risk of heart failure. Evidence from in vivo studies demonstrated that CNI prolong the duration of action potentials through a decrease in potassium current. CNI also exerted direct effects on endothelial cell injury, inducing apoptosis and enhancing oxidative stress. CNI may induce vascular inflammation through TLR4 via MyD88 and TRIF pathways. In addition, CNI affects vascular function by impairing endothelial-dependent vasodilation and promoting vasoconstriction. Clinical studies in transplant patients also revealed an increased incidence of cardiac remodeling. However, the evidence is constrained by the limited number of participants and potential confounding factors. Several studies indicate differing cardiovascular toxicity profiles between CsA and TAC, and these could be potentially due to their different interactions with calcineurin subunits and calcineurin-independent effects. Further studies are needed to clarify these mechanisms to improve cardiovascular outcomes for transplant patients with CNI.

Management of ROS and Regulatory Cell Death in Myocardial Ischemia-Reperfusion Injury

Myocardial ischemia-reperfusion injury (MIRI) is fatal to patients, leading to cardiomyocyte death and myocardial remodeling. Reactive oxygen species (ROS) and oxidative stress play important roles in MIRI. There is a complex crosstalk between ROS and regulatory cell deaths (RCD) in cardiomyocytes, such as apoptosis, pyroptosis, autophagy, and ferroptosis. ROS is a double-edged sword. A reasonable level of ROS maintains the normal physiological activity of myocardial cells. However, during myocardial ischemia-reperfusion, excessive ROS generation accelerates myocardial damage through a variety of biological pathways. ROS regulates cardiomyocyte RCD through various molecular mechanisms. Targeting the removal of excess ROS has been considered an effective way to reverse myocardial damage. Many studies have applied antioxidant drugs or new advanced materials to reduce ROS levels to alleviate MIRI. Although the road from laboratory to clinic has been difficult, many scholars still persevere. This article reviews the molecular mechanisms of ROS inhibition to regulate cardiomyocyte RCD, with a view to providing new insights into prevention and treatment strategies for MIRI.

Moderate exercise mitigates cardiac dysfunction and injury induced by cyclosporine A through activation of the PGI2 / PPAR-γ signaling pathway

Background and purpose

The present study investigated the role of the prostaglandin I2/peroxisome proliferator activator receptor (PGI2/PPAR) signaling pathway in cardiac cell proliferation, apoptosis, and systemic hemodynamic variables under cyclosporine A (CsA) exposure alone or combined with moderate exercises.

Experimental approach

Twenty-four male Wistar rats were classified into three groups, namely, control, CsA, and CsA + exercise.

Findings/Results

After 42 days of treatment, the findings showed a significant enhancement in the expression of the β-MHC gene, enhancement in protein expression of Bax and caspase-3, and a significant decline in the protein expression of Bcl-2 expression, as well as increased proliferation intensity in the heart tissue of the CsA group compared to the control group. Systolic pressure, pulse pressure, mean arterial pressure (MAP), QT and QRS duration, and T wave amplitude, as well as QTc amount in the CsA group, showed a significant increase compared to the control group. PPAR-γ and PGI2 showed no significant changes compared to the control group. Moderate exercise along with CsA significantly enhanced the protein expression of PPAR-γ and PGI2 and declined protein expression of Bax, and caspase-3 compared to those in the CsA group. In the CsA + exercise group, systolic pressure, MAP, and Twave showed a significant decrease compared to the CsA group. Moderate exercises along CsA improved heart cell proliferation intensity and significantly reduced β- MHC gene expression compared to the CsA group.

Conclusions and implications

The results showed moderate exercise alleviated CsA-induced heart tissue apoptosis and proliferation with the corresponding activation of the PGI2/PPAR-γ pathway.

PDZK1 improves ventricular remodeling in hypertensive rats by regulating the stability of the Mas receptor

Ventricular remodeling is one of the main causes of mortality from heart failure due to hypertension. Exploring its mechanism and finding therapeutic targets have become urgent scientific problems to be solved. A number of studies have shown that Mas, as an Ang-(1-7) specific receptor, was significantly reduced in myocardial tissue of rats undergoing hypertensive ventricular remodeling. It has been reported that Mas receptor levels are significantly downregulated in myocardium undergoing ventricular remodeling, but studies focused on intracellular and post-translational modifications of Mas are lacking. The results of this research are as follows: (1) PDZK1 interacts with the carboxyl terminus of Mas through its PDZ1 domain; (2) the expression of PDZK1 and Mas is decreased in rats undergoing hypertensive ventricular remodeling, and PDZK1 upregulation can ameliorate hypertensive myocardial fibrosis and myocardial hypertrophy; (3) PDZK1 enhances the stability of Mas protein through the proteasome pathway, and the proteasome inhibitor MG132 promotes hypertensive ventricular remodeling. PDZK1 improves ventricular remodeling in hypertensive rats by regulating Mas receptor stability. This study provides a scientific basis for the prevention and treatment of ventricular remodeling.

Anti-inflammatory role of extracellular l-arginine through calcium sensing receptor in human renal proximal tubular epithelial (HK-2) cells

Renal tubular epithelial cells are capable of synthesizing interleukins (IL) in response to a variety of proinflammatory cytokines. Moreover, elevated urinary levels of IL have been shown in patients with various forms of nephritic diseases. However, the underlying intracellular signaling mechanism is unclear. Here we show the immunological signaling role of l-Arginine (l-Arg) through Ca2+-sensing receptor (CaSR) in human kidney 2 (HK-2) renal proximal tubular epithelial cells, using Ca2+ imaging and patch clamp techniques and its mechanistic link to the downstream cellular function. Both pharmacological and siRNA inhibitors support the activation CaSR by extracellular l-Arg to induced Ca2+ entry via a Transient receptor potential canonical (TRPC) channel in HK-2 cells mainly through the receptor operated Ca2+ entry (ROCE). Activation of CaSR by l-Arg led to the rise in p-p38/p38 expression suggesting [Ca2+]i as a regulator for p38-signaling pathways. Notably, l-Arg activated CaSR-induced Ca2+ signaling reduced the expressions of key fibrotic, inflammatory, and apoptotic genes, suggesting its nephroprotective role via Ca2+ signaling through CaSR in HK-2 cells. Since we found that the IL-6 expressions were inversely proportional to the increasing concentrations of l-Arg in HK-2 cells, we measured the release of IL-6, which steadily decreased as the concentrations of l-Arg were elevated. Taken together, extracellular l-Arg is a negative regulator for IL-6-induced inflammatory process, through the activation of CaSR and TRPC channel by ROCE pathway and can have a potential to alleviate inflammatory renal diseases.

ERK: A Double-Edged Sword in Cancer. ERK-Dependent Apoptosis as a Potential Therapeutic Strategy for Cancer

The RAF/MEK/ERK signaling pathway regulates diverse cellular processes as exemplified by cell proliferation, differentiation, motility, and survival. Activation of ERK1/2 generally promotes cell proliferation, and its deregulated activity is a hallmark of many cancers. Therefore, components and regulators of the ERK pathway are considered potential therapeutic targets for cancer, and inhibitors of this pathway, including some MEK and BRAF inhibitors, are already being used in the clinic. Notably, ERK1/2 kinases also have pro-apoptotic functions under certain conditions and enhanced ERK1/2 signaling can cause tumor cell death. Although the repertoire of the compounds which mediate ERK activation and apoptosis is expanding, and various anti-cancer compounds induce ERK activation while exerting their anti-proliferative effects, the mechanisms underlying ERK1/2-mediated cell death are still vague. Recent studies highlight the importance of dual-specificity phosphatases (DUSPs) in determining the pro- versus anti-apoptotic function of ERK in cancer. In this review, we will summarize the recent major findings in understanding the role of ERK in apoptosis, focusing on the major compounds mediating ERK-dependent apoptosis. Studies that further define the molecular targets of these compounds relevant to cell death will be essential to harnessing these compounds for developing effective cancer treatments.

Hurdles to Cardioprotection in the Critically Ill

Cardiovascular disease is the largest contributor to worldwide mortality, and the deleterious impact of heart failure (HF) is projected to grow exponentially in the future. As heart transplantation (HTx) is the only effective treatment for end-stage HF, development of mechanical circulatory support (MCS) technology has unveiled additional therapeutic options for refractory cardiac disease. Unfortunately, despite both MCS and HTx being quintessential treatments for significant cardiac impairment, associated morbidity and mortality remain high. MCS technology continues to evolve, but is associated with numerous disturbances to cardiac function (e.g., oxidative damage, arrhythmias). Following MCS intervention, HTx is frequently the destination option for survival of critically ill cardiac patients. While effective, donor hearts are scarce, thus limiting HTx to few qualifying patients, and HTx remains correlated with substantial post-HTx complications. While MCS and HTx are vital to survival of critically ill cardiac patients, cardioprotective strategies to improve outcomes from these treatments are highly desirable. Accordingly, this review summarizes the current status of MCS and HTx in the clinic, and the associated cardiac complications inherent to these treatments. Furthermore, we detail current research being undertaken to improve cardiac outcomes following MCS/HTx, and important considerations for reducing the significant morbidity and mortality associated with these necessary treatment strategies.

Calcium‑sensing receptors in human peripheral T lymphocytes and AMI: Cause and effect

Acute myocardial infarction (AMI) is a disease associated with inflammation. T lymphocytes are involved by secreting cytokines and inflammatory factors. In our previous study, it was found that the T lymphocytes exhibited certain functional changes, the onset of which was induced by modulating calcium‑sensing receptor (CaSR) in AMI. In the present study, western blotting was used to verified the expression of T lymphocyte CaSR and pathway proteins, including phosphorylated extracellular signal‑regulated kinase (P‑ERK)1/2 and phosphorylated c‑Jun N‑terminal kinase (P‑JNK), and used cytometric bead array to detect the secretion of interleukin (IL)‑4, IL‑6, IL‑10 and tumor necrosis factor (TNF)‑α in AMI onset, the results demonstrated that they were all increased. In addition, the expression of T lymphocyte pathway proteins, including P‑ERK1/2 and P‑JNK, and the secretion of IL‑4, IL‑6, IL‑10 and TNF‑α decreased after T lymphocytes being transfected by CaSR small interfering RNA. By contrast, the neonatal mouse cardiomyocytes under hypoxia and hypoxia/re‑oxygenation exhibited ultrastructural damage, increased apoptosis, increased production of lactate dehydrogenase (LDH) and malondialdehyde, and reduced superoxide dismutase; these indicators changed extensively when cardiomyocytes were co‑cultured with T lymphocytes. However, the effects were reversed when the cardiomyocytes were co‑cultured with CaSR‑silenced T lymphocytes. These results indicated that CaSR may modulate T lymphocytes to release cytokines through mitogen‑activated protein kinase pathways and affect cardiomyocyte injury. The relationship between AMI and T lymphocyte CaSR is reciprocal.

Vascular Delivery of Allogeneic MuStem Cells in Dystrophic Dogs Requires Only Short-Term Immunosuppression to Avoid Host Immunity and Generate Clinical/Tissue Benefits

Growing demonstrations of regenerative potential for some stem cells led recently to promising therapeutic proposals for neuromuscular diseases. We have shown that allogeneic MuStem cell transplantation into Golden Retriever muscular dystrophy (GRMD) dogs under continuous immunosuppression (IS) leads to persistent clinical stabilization and muscle repair. However, long-term IS in medical practice is associated with adverse effects raising safety concerns. Here, we investigate whether the IS removal or its restriction to the transplantation period could be considered. Dogs aged 4-5 months old received vascular infusions of allogeneic MuStem cells without IS (GRMDMU/no-IS) or under transient IS (GRMDMU/tr-IS). At 5 months post-infusion, persisting clinical status improvement of the GRMDMU/tr-IS dogs was observed while GRMDMU/no-IS dogs exhibited no benefit. Histologically, only 9-month-old GRMDMU/tr-IS dogs showed an increased muscle regenerative activity. A mixed cell reaction with the host peripheral blood mononucleated cells (PBMCs) and corresponding donor cells revealed undetectable to weak lymphocyte proliferation in GRMDMU/tr-IS dogs compared with a significant proliferation in GRMDMU/no-IS dogs. Importantly, any dog group showed neither cellular nor humoral anti-dystrophin responses. Our results show that transient IS is necessary and sufficient to sustain allogeneic MuStem cell transplantation benefits and prevent host immunity. These findings provide useful critical insight to designing therapeutic strategies.

The Different Facets of Extracellular Calcium Sensors: Old and New Concepts in Calcium-Sensing Receptor Signalling and Pharmacology

The current interest of the scientific community for research in the field of calcium sensing in general and on the calcium-sensing Receptor (CaR) in particular is demonstrated by the still increasing number of papers published on this topic. The extracellular calcium-sensing receptor is the best-known G-protein-coupled receptor (GPCR) able to sense external Ca2+ changes. Widely recognized as a fundamental player in systemic Ca2+ homeostasis, the CaR is ubiquitously expressed in the human body where it activates multiple signalling pathways. In this review, old and new notions regarding the mechanisms by which extracellular Ca2+ microdomains are created and the tools available to measure them are analyzed. After a survey of the main signalling pathways triggered by the CaR, a special attention is reserved for the emerging concepts regarding CaR function in the heart, CaR trafficking and pharmacology. Finally, an overview on other Ca2+ sensors is provided.

Cyclosporin A induces autophagy in cardiac fibroblasts through the NRP-2/WDFY-1 axis

Cyclosporin A (CsA) is an effective immunosuppressive agent, but its myocardial toxicity limits its widespread and long-term clinical application. In this study, CsA treatment led to damages in myocardial fiber structure, an increase in myocardial fibrosis, and changes in heart size and shape; moreover, the degree of damage was exacerbated with prolonged drug application and increases in dose. However, the mechanism is not clear; therefore, the purpose of this study was to reveal the mechanism of CsA-induced myocardial fibrosis and identify a new target for the prevention and treatment of CsA-induced myocardial injury. Cardiac fibroblasts were treated with CsA (5, 10, or 20 μg/mL) for 24 h. Autophagy was observed by electron microscopy and immunofluorescence. The expression of NRP-2/WDFY-1, autophagy-related proteins (Beclin1 and LC3B), fibrosis-related proteins (MMP2/9), and fibroblast phenotype conversion factor (α-SMA) was evaluated by Western blot. The expression of collagen I was determined by ELISA. Then, we used the gene interference technique to alter WDFY-1 expression with or without CsA or 3-MA treatment for 24 h, and the effects on autophagy and the expression of autophagy-related proteins, fibrosis-associated proteins, IFN-α, TNF-α, and IL-6 were determined. The results showed the following: (1) CsA induced fibrosis-related protein (MMP2/9), fibroblast phenotype conversion factor (α-SMA), and collagen I up-regulation in a dose-dependent manner. (2) CsA induced the formation of autophagosomes and up-regulated the expression of Beclin1, LC3B, and the ERK/MAPK pathway in cardiac fibroblasts. (3) CsA induced NRP-2 down-regulation and WDFY-1 up-regulation. (4) Depletion of WDFY-1 inhibited CsA-induced autophagy, TNF-α and IFN-α up-regulation, and fibrosis. (5) The autophagy inhibitor 3-MA inhibited CsA-induced TNF-α and IFN-α up-regulation and fibrosis. Overall, cyclosporin A induces autophagy in cardiac fibroblasts through the NRP-2/WDFY-1 axis, which promotes the progression of myocardial fibrosis.

Role of autophagy in cadmium-induced testicular injury

The testis is sensitive to cadmium, but studies investigating cadmium-induced testicular injury have not yet clearly revealed the underlying mechanisms. This study aimed to investigate the injurious effects of cadmium on rat testes and the role that autophagy plays in this process. Wistar rats were randomly divided into four groups and intraperitoneally injected with 0.2 (low), 0.4 (middle), and 0.8 mg/kg·body weight (high) cadmium chloride for 5 weeks, while the control rats were injected with equal volume of saline. Rats exposed to cadmium appeared inactive and had reduced body weights and increased testicular organ coefficients at the end of treatment compared with control rats. Atomic absorption results showed that cadmium levels increased with increased cadmium exposure. Hematoxylin and eosin staining of testicular sections showed seminiferous tubular atrophy, decreased pipe diameter, spermatogonial stem cells falling off the inner lining, and reduced germ cell layers of disorderly arrangements in cadmium-treated rats. Immunohistochemical and western blot results both showed that levels of the autophagy-related proteins Beclin1 and microtubule-associated protein 1 light chain 3B (LC3B) increased with increased cadmium exposure. We also found that LC3B-II and calcium-sensing receptor (CSR) levels in cadmium-exposed rats significantly increased. By immunofluorescence, we found that the percentage of cells that expressed the CSR was significantly higher in LC3B-positive than LC3B-negative cells. Together, our results showed that cadmium accumulates in the testes causing testicular injury, which may be related to increased autophagy levels. Furthermore, calcium disorders associated with the CSR may reveal a potential way to activate autophagy.

Calcium Oxalate Induces Renal Injury through Calcium-Sensing Receptor

Objective. To investigate whether calcium-sensing receptor (CaSR) plays a role in calcium-oxalate-induced renal injury. Materials and Methods. HK-2 cells and rats were treated with calcium oxalate (CaOx) crystals with or without pretreatment with the CaSR-specific agonist gadolinium chloride (GdCl₃) or the CaSR-specific antagonist NPS2390. Changes in oxidative stress (OS) in HK-2 cells and rat kidneys were assessed. In addition, CaSR, extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal protein kinase (JNK), and p38 expression was determined. Further, crystal adhesion assay was performed in vitro, and the serum urea and creatinine levels and crystal deposition in the kidneys were also examined. Results. CaOx increased CaSR, ERK, JNK, and p38 protein expression and OS in vitro and in vivo. These deleterious changes were further enhanced upon pretreatment with the CaSR agonist GdCl₃ but were attenuated by the specific CaSR inhibitor NPS2390 compared with CaOx treatment alone. Pretreatment with GdCl₃ further increased in vitro and in vivo crystal adhesion and renal hypofunction. In contrast, pretreatment with NPS2390 decreased in vitro and in vivo crystal adhesion and renal hypofunction. Conclusions. CaOx-induced renal injury is related to CaSR-mediated OS and increased mitogen-activated protein kinase (MAPK) signaling, which subsequently leads to CaOx crystal adhesion.

Fragment-based discovery of a new family of non-peptidic small-molecule cyclophilin inhibitors with potent antiviral activities

Cyclophilins are peptidyl-prolyl cis/trans isomerases (PPIase) that catalyse the interconversion of the peptide bond at proline residues. Several cyclophilins play a pivotal role in the life cycle of a number of viruses. The existing cyclophilin inhibitors, all derived from cyclosporine A or sanglifehrin A, have disadvantages, including their size, potential for side effects unrelated to cyclophilin inhibition and drug–drug interactions, unclear antiviral spectrum and manufacturing issues. Here we use a fragment-based drug discovery approach using nucleic magnetic resonance, X-ray crystallography and structure-based compound optimization to generate a new family of non-peptidic, small-molecule cyclophilin inhibitors with potent in vitro PPIase inhibitory activity and antiviral activity against hepatitis C virus, human immunodeficiency virus and coronaviruses. This family of compounds has the potential for broad-spectrum, high-barrier-to-resistance treatment of viral infections.

Cyclophilins play a key role in the life cycle of many viruses and represent important drug targets for broad-spectrum antiviral therapies. Here, the authors use fragment-based drug discovery to develop non-peptidic inhibitors of human cyclophilins with high activity against replication of a number of viral families.

Fullerene mediates proliferation and cardiomyogenic differentiation of adipose-derived stem cells via modulation of MAPK pathway and cardiac protein expression

Zero-dimensional fullerenes can modulate the biological behavior of a variety of cell lines. However, the effects and molecular mechanisms of proliferation and cardiomyogenic differentiation in brown adipose-derived stem cells (BADSCs) are still unclear. In this study, we report the initial biological effects of fullerene-C₆₀ on BADSCs at different concentrations. Results suggest that fullerene-C₆₀ has no cytotoxic effects on BADSCs even at a concentration of 100 μg/mL. Fullerene-C₆₀ improves the MAPK expression level and stem cell survival, proliferation, and cardiomyogenesis. Further, we found that the fullerene-C₆₀ modulates cardiomyogenic differentiation. Fullerene-C₆₀ improves the expression of cardiomyocyte-specific proteins (cTnT and α-sarcomeric actinin). At elevated concentration, fullerene-C₆₀ reduces the incidence of diminished spontaneous cardiac differentiation of BADSCs with time. At the genetic level, fullerene-C₆₀ (5 μg/mL) also improves the expression of cTnT. In addition, fullerene-C₆₀ promotes the formation of gap junction among cells. These findings have important implications for clinical application of fullerenes in the treatment of myocardial infarction.

Calcium homeostasis in mitochondrion-mediated apoptosis of chick embryo cecal epithelial cells induced by Eimeria tenella infection

In this study, the process of Eimeria tenella-induced apoptosis and the effect of calcium homeostasis were investigated in chick embryo cecal epithelial cells. In particular, we examined cytochrome c release into the cytoplasm, mitochondrial permeability transition pore (MPTP) opening, and changes in [Ca(2+)]c and apoptosis in host cells. Apoptosis, MPTP opening, cytochrome c release, and [Ca(2+)]c in host cells increased following infection. This trend was reversed by blocking the increase in [Ca(2+)]c using BAPTA/AM and EGTA (intra- and extracellular chelators of Ca(2+), respectively) and by applying heparin sodium and ryanodine (blockers of the inositol triphosphate and ryanodine receptors of the endoplasmic reticulum, respectively). These results indicate that [Ca(2+)]c plays a significant role in host cell mitochondrial apoptosis, which is induced via modulation of extracellular Ca(2+) levels and endoplasmic reticulum Ca(2+) channels. Thus, agents that restore Ca(2+) homeostasis may be useful for managing E. tenella infection in chickens.

Cyclosporin A upregulates ETB receptor in vascular smooth muscle via activation of mitogen-activating protein kinases and NF-κB pathways

Hypertension is one of the most frequent complications of solid organ transplantation, and cyclosporin A (CsA) plays a predominant role in the pathophysiology of post-transplant hypertension. However, the exact molecular mechanisms of CsA-induced hypertension remain obscure. We previously showed that CsA increased the mRNA expression and contractile function of endothelin B (ETB) receptor in vascular smooth muscle cells. The present study was designed to investigate the underlying mechanisms of CsA-induced upregulation of ETB receptor in vasculature. Rat mesenteric arteries were incubated with CsA in an organ culture system, and results showed that CsA enhanced ETB receptor mRNA in the time- and dose-dependent manner, and increased protein expression levels of ETB receptor after treatment with CsA 10(-5)M for 6h. Furthermore, CsA induced phosphorylation of extracellular regulated protein kinases 1 and 2 (ERK1/2), p38, and translocation of nuclear factor-kappaB (NF-κB) p65 in vasculature. Blocking ERK1/2, p38, or NF-κB activation with their specific inhibitors markedly attenuated CsA-induced upregulation of ETB receptor mRNA expression and protein levels, and ETB receptor-mediated contraction. In summary, this study showed that mitogen-activating protein kinases (ERK1/2 and p38) and the downstream transcriptional factor NF-κB pathways were involved in CsA-induced upregulation of ETB receptor in arterial smooth muscle cells.

Mineral trioxide aggregate upregulates odonto/osteogenic capacity of bone marrow stromal cells from craniofacial bones via JNK and ERK MAPK signalling pathways

OBJECTIVES

The aim of this study was to investigate effects of mineral trioxide aggregate (MTA) on odonto/osteogenic differentiation of bone marrow stromal cells (BMSCs) from craniofacial bones.

MATERIALS AND METHODS

Craniofacial BMSCs were isolated from rat mandible and effects of MTA on their proliferation, differentiation and MAPK pathway involvement were subsequently investigated, in vitro. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2,5-tetrazoliumbromide) assay was performed to evaluate proliferation of the MTA-treated cells. Alkaline phosphatase (ALP) activity, alizarin red staining, real-time reverse transcription polymerase chain reaction and western blot assays were used to assess differentiation capacity as well as MAPK pathway involvement.

RESULTS

0.02 mg/ml MTA-treated BMSCs had significantly higher ALP activity and formed more mineralized nodules than the untreated group. Odonto/osteoblastic marker genes/proteins (Alp, Runx2/RUNX2, Osx/OSX, Ocn/OCN and Dspp/DSP respectively) in MTA-treated cells were remarkably upregulated compared to untreated ones. Mechanistically, phosphorylated Jun N-terminal kinase (P-JNK) and phosphorylated extracellular regulated protein kinases (P-ERK) in MTA-treated BMSCs increased significantly in a time-dependent manner, while inhibition of JNK and ERK MAPK pathways dramatically blocked MTA-induced odonto/osteoblastic differentiation, as indicated by reduced ALP levels, weakened mineralization capacity and downregulated levels of odonto/osteoblastic marker genes (Alp, Runx2, Osx, Ocn and Dspp).

CONCLUSION

Mineral trioxide aggregate promoted odonto/osteogenic capacity of craniofacial BMSCs via JNK and ERK MAPK signalling pathways.

Nicotine promotes cell proliferation and induces resistance to cisplatin by α7 nicotinic acetylcholine receptor‑mediated activation in Raw264.7 and El4 cells

Although nicotine is a risk factor for carcinogenesis and atherosclerosis, epidemiological data indicate that nicotine has therapeutic benefits in treating Alzheimer's disease. Our previous studies also showed that nicotine-treated dendritic cells have potential antitumor effects. Hence, the precise effects of nicotine on the biological characterizations of cells are controversial. The aim of the present study was to assess the roles of α7 nicotinic acetylcholine receptors (nAChRs), Erk1/2-p38-JNK and PI3K-Akt pathway in nicotine-mediated proliferation and anti-apoptosis effects. The results firstly showed that nicotine treatment clearly augmented cell viability and upregulated PCNA expression in both Raw264.7 and El4 cells. Meanwhile, nicotine afforded protection against cisplatin-induced toxicity through inhibiting caspase-3 activation and upregulating anti-apoptotic protein expression. Further exploration demonstrated that nicotine efficiently abolished cisplatin-promoted mitochondria translocation of Bax and the release of cytochrome c. The pretreatment of α-bungarotoxin and tubocurarine chloride significantly attenuated nicotine-augmented cell viability, abolished caspase-3 activation and α7 nAChR upregulation. Both Erk-JNK-p38 and PI3K-Akt signaling pathways could be activated by nicotine treatment in Raw264.7 and El4 cells. Notably, when Erk-JNK and PI3K-Akt activities were inhibited, nicotine-augmented cell proliferation and anti-apoptotic effects were abolished accordingly. The results presented here indicate that nicotine could achieve α7 nAChR-mediated proliferation and anti-apoptotic effects by activating Erk-JNK and PI3K-Akt pathways respectively, providing potential therapeutic molecules to deal with smoking-associated human diseases.

Calcium paradox induces apoptosis in the isolated perfused Rana ridibunda heart: involvement of p38-MAPK and calpain

“Calcium paradox” as a term describes the deleterious effects conferred to a heart perfused with a calcium-free solution followed by repletion, including loss of mechanical activity and sarcomere disruption. Given that the signaling mechanisms triggered by calcium paradox remain elusive, in the present study, we tried to investigate them in the isolated perfused heart from Rana ridibunda. Calcium paradox was found to markedly activate members of the MAPKs (p43-ERK, JNKs, p38-MAPK). In addition to lactate dehydrogenase (LDH) release in the perfusate (indicative of necrosis), we also confirmed the occurrence of apoptosis by using the TUNEL assay and identifying poly(ADP-ribose) polymerase (PARP) fragmentation and upregulated Bax expression. Furthermore, using MDL28170 (a selective calpain inhibitor), a role for this protease was revealed. In addition, various divalent cations were shown to exert a protective effect against the calcium paradox. Interestingly, SB203580, a p38-MAPK inhibitor, alleviated calcium-paradox-conferred apoptosis. This result indicates that p38-MAPK plays a pro-apoptotic role, contributing to the resulting myocardial dysfunction and cell death. To our knowledge, this is the first time that the calcium paradox has been shown to induce apoptosis in amphibians, with p38-MAPK and calpain playing significant roles.

LPS induces cardiomyocyte injury through calcium-sensing receptor

Calcium-sensing receptor (CaSR) belongs to the family C of G-protein coupled receptors. We have previously demonstrated that CaSR could induce apoptosis of cultured neonatal rat ventricular cardiomyocytes in simulated ischemia/reperfusion. It remains unknown whether the CaSR has function in lipopolysaccharide (LPS)-induced myocardial injure. The aim of this study was to investigate whether the CaSR plays a role in LPS-induced myocardial injury. Cultured neonatal rat cardiomyocytes were treated with LPS, with or without pretreatment with the CaSR-specific agonist gadolinium chloride (GdCl3) or the CaSR-specific antagonist NPS2390. Release of TNF-α and IL-6 from cardiomyocytes was observed. Levels of malonaldehyde (MDA), lactate dehydrogenase (LDH), and activity of superoxide dismutase (SOD) were measured. In addition, apoptosis of the cardiomyocytes, [Ca(2+)]i and level of CaSR expression were determined. The results showed that LPS increased cardiomyocytes apoptosis, [Ca(2+)]i, MDA, LDH, TNF-α, IL-6 release, and CaSR protein expression. Compared with LPS treatment alone, pretreatment with GdCl3 further increased apoptosis of cardiomyocytes, MDA, LDH, TNF-α, IL-6 release, [Ca(2+)]i, and the expression of the CaSR protein. Conversely, pretreatment with NPS2390 decreased apoptosis of cardiomyocytes, MDA, LDH, TNF-α, IL-6 release, [Ca(2+)]i and the expression of the CaSR protein. These results demonstrate that LPS could induce cardiomyocyte injury. Moreover, LPS-induced cardiomyocyte injury was related to CaSR-mediated cardiomyocytes apoptosis, TNF-α, IL-6 release, and increase of intracellular calcium.