Diltiazem reduces apoptosis in rat hepatocytes subjected to warm hypoxia-reoxygenation

Mitochondrial Effects of Common Cardiovascular Medications: The Good, the Bad and the Mixed

Mitochondria are central organelles in the homeostasis of the cardiovascular system via the integration of several physiological processes, such as ATP generation via oxidative phosphorylation, synthesis/exchange of metabolites, calcium sequestration, reactive oxygen species (ROS) production/buffering and control of cellular survival/death. Mitochondrial impairment has been widely recognized as a central pathomechanism of almost all cardiovascular diseases, rendering these organelles important therapeutic targets. Mitochondrial dysfunction has been reported to occur in the setting of drug-induced toxicity in several tissues and organs, including the heart. Members of the drug classes currently used in the therapeutics of cardiovascular pathologies have been reported to both support and undermine mitochondrial function. For the latter case, mitochondrial toxicity is the consequence of drug interference (direct or off-target effects) with mitochondrial respiration/energy conversion, DNA replication, ROS production and detoxification, cell death signaling and mitochondrial dynamics. The present narrative review aims to summarize the beneficial and deleterious mitochondrial effects of common cardiovascular medications as described in various experimental models and identify those for which evidence for both types of effects is available in the literature.

Synthetic cannabinoid CP-55,940 induces apoptosis in a human skeletal muscle model via regulation of CB1 receptors and L-type Ca2+ channels

Rhabdomyolysis has been reported in patients who abuse synthetic cannabinoids. However, no studies have yet assessed whether these cases reflect the direct cytotoxicity of synthetic cannabinoids on skeletal muscle, a possibility that the present study sought to address. Specifically, this study investigated the cytotoxicity of the synthetic cannabinoid CP-55,940, a compound that acts equally on both types of cannabinoid receptors (CB₁ and CB₂), in a human embryonic rhabdomyosarcoma (RD) cell line. Exposure of these cells to CP-55,940 resulted in concentration-dependent decreases in cell viability. These effects were attenuated by pre-incubation with AM251 (30 µM), a selective CB₁ receptor antagonist, but not by pre-incubation with AM630 (30 µM), a selective CB₂ receptor antagonist. Following treatment with CP-55,940, RD cells exhibited apoptosis, as indicated by the accumulation of annexin-V, activation of caspase-3, and a loss of the mitochondrial membrane potential. Additionally, CP-55,940 treatment of RD cells led to increases in intracellular Ca²⁺ levels. CP-55,940-induced cell death was significantly attenuated in the absence of extracellular Ca²⁺, and was partially decreased by pre-incubation with verapamil (5 µM) or diltiazem (5 µM), compounds that block the L-type Ca²⁺ channel. Our results indicate that the cytotoxicity of CP-55,940 towards RD cells (skeletal muscle cells) is mediated by the CB₁ receptor, but not by the CB₂ receptor. Our results further suggest that calcium influx through the L-type channel may play an important role in the apoptosis induced by these compounds.

The Neuroprotective and Anti-inflammatory Effects of Diltiazem in Spinal Cord Ischaemia–Reperfusion Injury

The protective effects of diltiazem were examined in a rabbit model of spinal cord ischaemia–reperfusion induced by infrarenal aortic occlusion for 30 min. In the diltiazem group ( n = 6), an intravenous infusion (2 μg/kg per min) was started 10 min before ischaemia induction; normal saline solution was infused in the control group ( n = 6). Neurological function was assessed using modified Tarlov criteria 24 h after surgery. Plasma samples were analysed for interleukin (IL)-6 and IL-10. Spinal tissue was analysed for malondialdehyde, nitric oxide and reduced glutathione activities. Tarlov scores of the diltiazem-treated rabbits indicated significantly improved hind-limb motor function compared with the control group. The diltiazem group also had better quantitative and qualitative histopathological findings. Diltiazem infusion significantly reduced IL-6 levels 3 and 24 h after reperfusion compared with the control group. The mean IL-10 level in the diltiazem group was significantly higher than in the control group 24 h after reperfusion. It is concluded that diltiazem has cytoprotective and anti-inflammatory properties, leading to reduced spinal cord injury.

Attenuation of liver ischemia/reperfusion induced apoptosis by epigallocatechin-3-gallate via down-regulation of NF-kappaB and c-Jun expression

INTRODUCTION

Hepatic ischemia/reperfusion (I/R) activates Kupffer cells and initiates severe oxidative stress with enhanced production of reactive oxygen species (ROS) and tumor necrosis factor-alpha (TNF-alpha). ROS and TNF-alpha mediate the expression of nuclear factors and kinases, activating the signal transduction pathway, and triggering apoptosis. The aim of our study was to evaluate the potential protective effect of (-)-epigallocatechin-3-gallate (EGCG) administration in inhibition of apoptosis by attenuating the expression of NF-kappaB, c-Jun, and caspase-3 in a model of severe hepatic I/R.

MATERIALS AND METHODS

Thirty Wistar rats were allocated into three groups. Sham operation, I/R, and I/R-EGCG 50mg/kg. Hepatic ischemia was induced for 60min by Pringle's maneuver. Malondialdehyde (MDA), myeloperoxidase (MPO), light histology, scanning electron microscopy, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), and immunocytochemistry for NF-kappaB, c-Jun, caspase-3, analysis on liver specimens and aspartate (AST), and alanine (ALT) transferases analysis in serum, were performed 120min after reperfusion.

RESULTS

Apoptosis as indicated by TUNEL and caspase-3 was widely expressed in the I/R group but very limited in the EGCG treated group. Liver was stained positive for NF-kappaB and c-Jun in the I/R group but failed to be stained positive in the EGCG treated group. MDA, MPO, AST, and ALT showed marked increase in the I/R group and significant decrease in EGCG treated group. Significant alterations of liver specimens were observed by light histology and transmission electron microscopy whilst pretreatment with EGCG resulted in parenchymal preservation.

CONCLUSIONS

Administration of EGCG is likely to inhibit I/R-induced apoptosis and protect liver by down-regulating NF-kappaB and c-Jun signal transduction pathways.

Inhibition of intestinal ischemia/repurfusion induced apoptosis and necrosis via down-regulation of the NF-kB, c-Jun and caspace-3 expression by epigallocatechin-3-gallate administration

Intestinal ischemia/reperfusion (I/R) produces reactive oxygen species (ROS) activating signal transduction and apoptosis. The aim of this study was to evaluate the effect of (-)-epigallocatechin-3-gallate (EGCG) administration in inhibition of apoptosis by attenuating the expression of NF-kB, c-Jun and caspace-3 in intestinal I/R. Thirty male wistar rats were used. Group A sham operation, B I/R, C I/R-EGCG 50 mg/kg ip. Intestinal ischemia was induced for 60 min by clamping the superior mesenteric artery. Malondialdehyde (MDA), myeloperoxidase (MPO), light histology, Fragment End Labelling of DNA (TUNEL), immunocytochemistry for NF-kB, c-Jun and caspace-3 analysis in intestinal specimens were performed 120 min after reperfusion. Apoptosis as indicated by TUNEL and Caspace-3, NF-kB and c-Jun was widely expressed in I/R group but only slightly expressed in EGCG treated groups. MDA and MPO showed a marked increase in the I/R group and a significant decrease in the EGCG treated group. Light histology showed preservation of architecture in the EGCG treated group. In conclusion, EGCG pre-treatment is likely to inhibit intestinal I/R-induced apoptosis by down-regulating the expression of NF-kB, c-Jun and caspase-3.

Mitochondrial membrane permeabilization in cell death

Irrespective of the morphological features of end-stage cell death (that may be apoptotic, necrotic, autophagic, or mitotic), mitochondrial membrane permeabilization (MMP) is frequently the decisive event that delimits the frontier between survival and death. Thus mitochondrial membranes constitute the battleground on which opposing signals combat to seal the cell's fate. Local players that determine the propensity to MMP include the pro- and antiapoptotic members of the Bcl-2 family, proteins from the mitochondrialpermeability transition pore complex, as well as a plethora of interacting partners including mitochondrial lipids. Intermediate metabolites, redox processes, sphingolipids, ion gradients, transcription factors, as well as kinases and phosphatases link lethal and vital signals emanating from distinct subcellular compartments to mitochondria. Thus mitochondria integrate a variety of proapoptotic signals. Once MMP has been induced, it causes the release of catabolic hydrolases and activators of such enzymes (including those of caspases) from mitochondria. These catabolic enzymes as well as the cessation of the bioenergetic and redox functions of mitochondria finally lead to cell death, meaning that mitochondria coordinate the late stage of cellular demise. Pathological cell death induced by ischemia/reperfusion, intoxication with xenobiotics, neurodegenerative diseases, or viral infection also relies on MMP as a critical event. The inhibition of MMP constitutes an important strategy for the pharmaceutical prevention of unwarranted cell death. Conversely, induction of MMP in tumor cells constitutes the goal of anticancer chemotherapy.

Fascioscapulohumeral muscular dystrophy: a progressive degenerative disease that responds to diltiazem

The authors believe that with fascioscapulohumeral muscular dystrophy (FSHD), like Duchenne muscular dystrophy, there is Ca2+ dysregulation in the muscle cells. The dysregulated Ca2+ can cause cell death in various ways. One mechanism may be Ca2+ triggering abnormal levels of tumor necrosis factor (TNF-alpha). Another mechanism may involve excessive Ca2+ levels within the mitochondria which would cause this organelle's membrane to collapse ultimately inducing apoptosis and/or necrosis. With this in mind, it has been reported that in FSHD there is over expression of adenine nucleotide translocator-1 (ANT-1). This Ca2+ dependent protein, which is a component of the mitochondrial permeability transition pore, could be an important culprit in mitochondrial membrane collapse. Therefore, dysregulated Ca2+ as well as TNF-alpha, in addition to over-expression of ANT-1, may result in cell disruption ultimately causing the characteristic dystrophic muscle wasting. The present investigators have noted that some individuals with FSHD benefit from a regimen of diltiazem, a Ca2+ channel blocker. Initial results using diltiazem may represent the first beneficial treatment for a form of muscular dystrophy. Even if there is only a slowing of progression, this would be a positive first step. A combination of several different Ca2+ regulating agents and TNF-alpha inhibitors may be necessary to truly alter and/or reverse the deleterious effects of this form of muscular dystrophy.

Diltiazem suppresses collagen synthesis and IL-1beta-induced TGF-beta1 production on human peritoneal mesothelial cells

BACKGROUND

After long-term treatment with continuous ambulatory peritoneal dialysis (CAPD), some patients may develop peritoneal fibrosis. Peritoneal mesothelial cells (PMCs) participate in the inflammatory reactions in the peritoneal cavity, and transforming growth factor-beta1 (TGF-beta1) and interleukin-1beta (IL-1beta) are involved in peritoneal fibrosis. Diltiazem is used frequently in patients with CAPD to treat hypertension. The objectives of this study were to examine the effects of diltiazem on collagen- and IL-1beta-induced TGF-beta1 production on human PMCs and the signalling pathway of diltiazem in this induction.

METHODS

Human PMCs were cultured from the enzymatic disaggregation of human omentum. Collagen synthesis was measured by [3H]proline incorporation into pepsin-resistant, salt-precipitated collagen. The expression of collagen I and III, and TGF-beta1 mRNA was evaluated by northern blotting. The production of TGF-beta1 by human PMCs was measured by immunoassay. The changes of intracellular calcium level after adding Fura-2-AM were measured by fluorescence spectrophotometry. Western blotting was used to assess mitogen-activated protein kinase (MAPK) signalling proteins.

RESULTS

We found that diltiazem (<0.2 mM) inhibited collagen I and III mRNA expression and collagen syntheses on a dose-dependent basis. Diltiazem (0.2 mM) suppressed IL-1beta- (5 ng/ml) induced TGF-beta1 production on human PMCs at both the protein and mRNA levels. Diltiazem (0.2 mM) also inhibited IL-1beta- (5 ng/ml) induced collagen I and III mRNA expression. Intracellular calcium levels did not change after the treatment with diltiazem, IL-1beta or both. The IL-1beta-treated human PMCs increased phospho-JNK (stress-activated c-Jun N-terminal kinase) and phospho-p38 MAPK expression, while diltiazem could suppress this phenomenon.

CONCLUSIONS

Diltiazem suppressed collagen synthesis of human PMCs and inhibited IL-1beta-induced TGF-beta1 production on human PMCs. This signalling transduction may be through p38 MAPK and JNK pathways instead of intracellular calcium. These results suggest diltiazem to be a potential therapeutic regimen in preventing peritoneal fibrosis and support further in vivo studies.

MCP-1/CCL2 protects cardiac myocytes from hypoxia-induced apoptosis by a G(alphai)-independent pathway

Chemokines, in addition to their chemotactic properties, act upon resident cells within a tissue and mediate other cellular functions. In a previous study, we demonstrated that CCL2 protects cultured mouse neonatal cardiac myocytes from hypoxia-induced cell death. Leukocyte chemotaxis has been shown to contribute to ischemic injury. While the chemoattractant properties of CCL2 have been established, the protective effects of this chemokine suggest a novel role for CCL2 in myocardial ischemia/reperfusion injury. The present study examined the cellular signaling pathways that promote this protection. Treatment of cardiac myocyte cultures with CCL2 protected them from hypoxia-induced apoptosis. This protection was not mediated through the activation of G(alphai) signaling that mediates monocyte chemotaxis. Inhibition of the ERK1/2 signaling pathway abrogated CCL2 protection. Caspase 3 activation and JNK/SAPK phosphorylation were decreased in hypoxic myocytes co-treated with CCL2 as compared to hypoxia only-treated cultures. Expression of the Bcl-2 family proteins, Bcl-xL and Bag-1, was increased in CCL2-treated myocytes subjected to hypoxia. There was also downregulation of Bax protein levels as a result of CCL2 co-treatment. These data suggest that CCL2 cytoprotection and chemotaxis may occur through distinct signaling mechanisms.

Tissue oxygenation and capacity to deliver O2 do the two go together?

Oxidative phosphorylation is the most important source of energy in mammals. Oxygen capture, convective and diffusive oxygen transport as well as the final intracellular oxygen utilization within the mitochondria represent highly refined mechanisms, supervised by a variety of physiological control systems. Any disease process interfering with the delivery of oxygen to tissue will ultimately lead to an impairment of cellular energy production. Generally, cellular hypoxia may result from either reduced oxygen uptake (hypoxic hypoxia), reduced convective and diffusive oxygen transport (circulatory and anemic hypoxia), impaired oxygen consumption (histotoxic hypoxia), or a combination of these states. To effectively treat any of these conditions, it is mandatory to recognize the underlying specific alterations of oxidative metabolism. Identification of the various types of hypoxia as well as contemporary treatment surveillance strategies depend primarily on measuring oxygen partial pressure in inspiratory gas, blood (arterial, mixed-venous) and tissue (extracellular fluid), next to monitoring of various circulatory parameters. This review focuses (a) on the diagnostic value of different techniques used to monitor blood and tissue oxygenation and (b) on the effects of impaired capacity to deliver O2 on tissue oxygen delivery and consumption. The potential value of multiparametric monitoring in guiding specific treatment measures to improve oxygen delivery to tissue is highlighted.

Rat liver ischemia-reperfusion-induced apoptosis and necrosis are decreased by FK506 pretreatment

The aim of this study was to demonstrate that tacrolimus (FK506) has a hepatoprotective effect by reducing ischemia-reperfusion-induced apoptosis and necrosis, both of which lead to post-surgical liver dysfunction. An ischemia-reperfusion model and primary cultured rat hepatocytes subjected to hypoxic and reoxygenation phases, mimicking the surgical process, were used. c-Jun N-terminal kinase 1/stress-activated protein kinase 1 (JNK1/SAPK1) activation leads to caspase 3 activation, a trigger of apoptosis. The activation status of JNK1/SAPK1 was evaluated by immunoprecipitation or Western-blotting experiments. Apoptosis was assessed by measuring caspase activation and by TUNEL (terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate-biotin nick-end labeling) reaction. Necrosis was assessed histologically. Tacrolimus improved the survival rate of rats subjected to ischemia-reperfusion. After FK506 pretreatment, the liver necrosis rate was reduced, and ischemia-reperfusion-induced JNK1/SAPK1 activation and apoptosis were significantly decreased. In hypoxia-reoxygenation-subjected hepatocytes, tacrolimus reduced JNK1/SAPK1 and caspase 3 activation. In the liver, tacrolimus prevented ischemia-reperfusion-induced apoptosis and necrosis.

Direct measurement of hepatic tissue hypoxia by using a novel tcpO2/pCO2 monitoring system in comparison with near-infrared spectroscopy

BACKGROUND/AIMS

Hepatic hypoxia occurs during liver surgery and transplantation and it may also appear within liver tumours, correlating with prognosis and efficacy of the treatment. The present study measured liver tissue hypoxia by directly using near-infrared spectroscopy (NIRS) and a novel tcpO2/pCO2 monitoring system.

METHODS

Graded hypoxia was achieved in a rabbit model by a stepwise reduction of the fraction of inspired oxygen (FiO2) from 0.3 to 0.0. Animals were allowed to recover from hypoxia at FiO2 of 3.0 indicated by normalised arterial blood gas values. Hepatic tissue oxyhaemoglobin (HbO2), deoxyhaemoglobin (Hb), cytochrome oxidase (Cyt Ox), oxygen partial pressure (pO2) and carbon dioxide partial pressure (pCO2) were measured continuously with the help of NIRS and a Clark-type surface tcpO2/pCO2 monitoring system, throughout the period of hypoxaemia.

RESULTS

There was an immediate reduction in hepatic HbO2 with hypoxia and a simultaneous increase in hepatic Hb. Similarly, hepatic tissue pO2 decreased significantly but tissue pCO2 remained unchanged until the FiO2 was below 0.1. Hepatic HbO2 showed a positive correlation with tissue pO2 (r = 0.53, P < 0.001). Hepatic Hb showed a negative correlation with tissue pO2 (r = 0.47, P < 0.001). Hepatic Cyt Ox decreased significantly with an FiO2 of 0.1 or less and showed a positive correlation with hepatic tissue pO2 (r = 0.64, P < 0.001). A significant correlation was found between hepatic tissue pO2 and arterial blood pO2 (r = 0.44, P < 0.001). Arterial blood pCO2 also correlated with hepatic tissue pCO2 (r = 0.53, P < 0.001) measured by the tcpO2/pCO2 monitoring system.

CONCLUSION

The data from the present study suggest that, like NIRS, the tcpO2/pCO2 monitoring system can be reliably used for the direct monitoring of hepatic tissue oxygenation in vivo.