Nitric oxide inhibits myocardial apoptosis by preventing caspase-3 activity via S-nitrosylation

Endoplasmic Reticulum Selective Autophagy Alleviates Anthracycline-Induced Cardiotoxicity

Background

The administration of anthracycline drugs induces progressive and dose-related cardiac damage through several cytotoxic mechanisms, including endoplasmic reticulum (ER) stress. The unfolded protein response plays a crucial role for mitigating misfolded protein accumulation induced by excessive ER stress.

Objectives

We aimed to clarify whether endoplasmic reticulum-selective autophagy machinery (ER-phagy) serves as an alternative system to protect cardiomyocytes from ER stress caused by anthracycline drugs.

Methods

Primary cultured cardiomyocytes, H9c2 cell lines, and cardiomyocyte-specific transgenic mice, all expressing ss-RFP-GFP-KDEL proteins, were used as ER-phagy reporter models. We generated loss-of-function models using RNA interference or gene-trap mutagenesis techniques. We assessed phenotypes and molecular signaling pathways using immunoblotting, quantitative polymerase chain reaction, cell viability assays, immunocytochemical and histopathological analyses, and cardiac ultrasonography.

Results

The administration of doxorubicin (Dox) activated ER-phagy in ss-RFP-GFP-KDEL-transduced cardiomyocytes. In addition, Dox-induced cardiomyopathy models of ER-phagy reporter mice showed marked activation of ER-phagy in the myocardium compared to those of saline-treated mice. Quantitative polymerase chain reaction analyses revealed that Dox enhanced the expression of cell-cycle progression gene 1 (CCPG1), one of the ER-phagy receptors, in H9c2 cells. Ablation of CCPG1 in H9c2 cells resulted in the reduced ER-phagy activity, accumulation of proapoptotic proteins, and deterioration of cell survival against Dox administration. CCPG1-hypomorphic mice developed more severe deterioration in systolic function in response to Dox compared to wild-type mice.

Conclusions

Our findings highlight a compensatory role of CCPG1-driven ER-phagy in reducing Dox toxicity. With further study, ER-phagy may be a potential therapeutic target to mitigate Dox-induced cardiomyopathy.

IFN-γ-STAT1-ERK Pathway Mediates Protective Effects of Invariant Natural Killer T Cells Against Doxorubicin-Induced Cardiomyocyte Death

Doxorubicin (DOX)-induced cardiomyopathy has poor prognosis, and myocardial inflammation is intimately involved in its pathophysiology. The role of invariant natural killer T (iNKT) cells has not been fully determined in this disease. We here demonstrated that activation of iNKT cells by α-galactosylceramide (GC) attenuated DOX-induced cardiomyocyte death and cardiac dysfunction. αGC increased interferon (IFN)-γ and phosphorylation of signal transducers and activators of transcription 1 (STAT1) and extracellular signal-regulated kinase (ERK). Administration of anti-IFN-γ neutralizing antibody abrogated the beneficial effects of αGC on DOX-induced cardiac dysfunction. These findings emphasize the protective role of iNKT cells in DOX-induced cardiomyopathy via the IFN-γ-STAT1-ERK pathway.

Chronic exposure to nitric oxide sensitizes prostate cancer cells and improved ZnO/CisPt NPs cytotoxicity and selectivity

The co-therapy of common chemotherapeutics with nitric oxide (NO), an endogenous signaling molecule, is proposed as an alternative to sensitize cancer cells and enhance treatments' efficacy. Herein, we have synthesized cisplatin-releasing zinc oxide nanoparticles (ZnO/CisPt NPs), which promoted a sustained and pH targeted release, able to release a higher amount of CisPt at tumor microenvironment conditions. This material was combined with a chronic NO treatment, at low concentration, in prostate cancer cells (PC3). NO treatment enhanced the S-NO concentration in PC3 cells, suggesting the nitrosylation or transnitrosylation processes enhancement, which are directly related to S-NO binding to proteins, function alterations and cancer cells death. Indeed, these mechanisms directly impacted the cytotoxic effect of ZnO/CisPt NPs, inducing a 30 % higher viability reduction of PC3 cells after NO treatment, along with a higher selectivity index when compared to normal human fibroblasts (FN1).

Inhibition of Caspase 3 and Caspase 9 Mediated Apoptosis: A Multimodal Therapeutic Target in Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the significant causes of death and morbidity, and it is hence a focus of translational research. Apoptosis plays an essential part in the pathophysiology of TBI, and its inhibition may help overcome TBI's negative consequences and improve functional recovery. Although physiological neuronal death is necessary for appropriate embryologic development and adult cell turnover, it can also drive neurodegeneration. Caspases are principal mediators of cell death due to apoptosis and are critical for the required cleavage of intracellular proteins of cells committed to die. Caspase-3 is the major executioner Caspase of apoptosis and is regulated by a range of cellular components during physiological and pathological conditions. Activation of Caspase-3 causes proteolyzation of DNA repair proteins, cytoskeletal proteins, and the inhibitor of Caspase-activated DNase (ICAD) during programmed cell death, resulting in morphological alterations and DNA damage that define apoptosis. Caspase-9 is an additional crucial part of the intrinsic pathway, activated in response to several stimuli. Caspases can be altered post-translationally or by modulatory elements interacting with the zymogenic or active form of a Caspase, preventing their activation. The necessity of Caspase-9 and -3 in diverse apoptotic situations suggests that mammalian cells have at least four distinct apoptotic pathways. Continued investigation of these processes is anticipated to disclose new Caspase regulatory mechanisms with consequences far beyond apoptotic cell death control. The present review discusses various Caspase-dependent apoptotic pathways and the treatment strategies to inhibit the Caspases potentially.

Ribonucleotide reductase: Implications of thiol S-nitrosylation and tyrosine nitration for different subunits

Ribonucleotide reductase (RNR) is a multi-subunit enzyme responsible for catalyzing the rate-limiting step in the production of deoxyribonucleotides essential for DNA synthesis and repair. The active RNR complex is composed of multimeric R1 and R2 subunits. The RNR catalysis involves the formation of tyrosyl radicals in R2 subunits and thiyl radicals in R1 subunits. Despite the quaternary structure and cofactor diversity, all the three classes of RNR have a conserved cysteine residue at the active site which is converted into a thiyl radical that initiates the substrate turnover, suggesting that the catalytic mechanism is somewhat similar for all three classes of the RNR enzyme. Increased RNR activity has been associated with malignant transformation, cancer cell growth, and tumorigenesis. Efforts concerning the understanding of RNR inhibition in designing potent RNR inhibitors/drugs as well as developing novel approaches for antibacterial, antiviral treatments, and cancer therapeutics with improved radiosensitization have been made in clinical research. This review highlights the precise and potent roles of NO in RNR inhibition by targeting both the subunits. Under nitrosative stress, the thiols of the R1 subunits have been found to be modified by S-nitrosylation and the tyrosyl radicals of the R2 subunits have been modified by nitration. In view of the recent advances and progresses in the field of nitrosative modifications and its fundamental role in signaling with implications in health and diseases, the present article focuses on the regulations of RNR activity by S-nitrosylation of thiols (R1 subunits) and nitration of tyrosyl residues (R2 subunits) which will further help in designing new drugs and therapies.

Endogenous Hydrogen Sulfide Persulfidates Caspase-3 at Cysteine 163 to Inhibit Doxorubicin-Induced Cardiomyocyte Apoptosis

Doxorubicin (DOX) is an efficient antitumor anthracycline drug, but its cardiotoxicity adversely affects the prognosis of the patients. In this study, we explored whether endogenous gasotransmitter hydrogen sulfide (H₂S) could protect against DOX-induced cardiomyocyte apoptosis and its mechanisms. The results indicated that DOX significantly downregulated endogenous H₂S production and endogenous synthetase cystathionine γ-lyase (CSE) expression and obviously stimulated the apoptosis in H9C2 cells. The supplement of H₂S donor sodium hydrosulfide (NaHS) or overexpression of CSE inhibited DOX-induced H9C2 cell apoptosis. DOX enhanced the activities of caspase family members in cardiomyocytes, while NaHS attenuated DOX-enhanced caspase-3, caspase-2, and caspase-9 activities by 223.1%, 73.94%, and 52.29%, respectively. Therefore, taking caspase-3 as a main target, we demonstrated that NaHS or CSE overexpression alleviated the cleavage of caspase-3, suppressed caspase-3 activity, and inhibited the cleavage of poly ADP-ribose polymerase (PARP). Mechanistically, we found that H₂S persulfidated caspase-3 in H9C2 cells and human recombinant caspase-3 protein, while the thiol-reducing agent dithiothreitol (DTT) abolished H₂S-induced persulfidation of caspase-3 and thereby prevented the antiapoptotic effect of H₂S on caspase-3 in H9C2 cells. The mutation of caspase-3 C148S and C170S failed to block caspase-3 persulfidation by H₂S in H9C2 cells. However, caspase-3 C163S mutation successfully abolished the effect of H₂S on caspase-3 persulfidation and the corresponding protection of H9C2 cells. Collectively, these findings indicate that endogenous H₂S persulfidates caspase-3 at cysteine 163, inhibiting its activity and cardiomyocyte apoptosis. Sufficient endogenous H₂S might be necessary for the protection against myocardial cell apoptosis induced by DOX. The results of the study might open new avenues with respect to the therapy of DOX-stimulated cardiomyopathy.

Protein S-Nitrosylation Regulates Postmortem Beef Apoptosis through the Intrinsic Mitochondrial Pathway

The objective of the present study was to investigate the regulatory mechanism of protein S-nitrosylation on early postmortem beef muscle apoptosis. Beef semimembranosus (SM) muscles at 45 min postmortem were treated with nitric oxide (NO) donor, control (NaCl solution), or nitric oxide synthase (NOS) inhibitor for 24 h at 4 °C. Bcl-2 expression and mitochondrial membrane potential were significantly increased by the NO donor treatment at 6 h postmortem, while the NOS inhibitor group exhibited a lower Bcl-2 level and mitochondrial membrane potential in comparison with the control (P < 0.05). The cytochrome c expression analysis highlighted that NO donor incubation repressed cytochrome c release from mitochondria to the cytoplasm. Further, S-nitrosylation levels of caspase-3 and caspase-9 were elevated after incubation with the NO donor (P < 0.05), leading to decreased caspase-3 and caspase-9 activities (P < 0.05). The aforementioned findings imply that protein S-nitrosylation mediates postmortem apoptosis of beef SM through the mitochondrial apoptotic pathway.

A Novel Oxygen Carrier (M101) Attenuates Ischemia-Reperfusion Injuries during Static Cold Storage in Steatotic Livers

The combined impact of an increasing demand for liver transplantation and a growing incidence of nonalcoholic liver disease has provided the impetus for the development of innovative strategies to preserve steatotic livers. A natural oxygen carrier, HEMO2life^®, which contains M101 that is extracted from a marine invertebrate, has been used for static cold storage (SCS) and has shown superior results in organ preservation. A total of 36 livers were procured from obese Zucker rats and randomly divided into three groups, i.e., control, SCS-24H and SCS-24H + M101 (M101 at 1 g/L), mimicking the gold standard of organ preservation. Ex situ machine perfusion for 2 h was used to evaluate the quality of the livers. Perfusates were sampled for functional assessment, biochemical analysis and subsequent biopsies were performed for assessment of ischemia-reperfusion markers. Transaminases, GDH and lactate levels at the end of reperfusion were significantly lower in the group preserved with M101 (p < 0.05). Protection from reactive oxygen species (low MDA and higher production of NO2-NO3) and less inflammation (HMGB1) were also observed in this group (p < 0.05). Bcl-1 and caspase-3 were higher in the SCS-24H group (p < 0.05) and presented more histological damage than those preserved with HEMO2life^®. These data demonstrate, for the first time, that the addition of HEMO2life^® to the preservation solution significantly protects steatotic livers during SCS by decreasing reperfusion injury and improving graft function.

Molecular mechanisms by which iNOS uncoupling can induce cardiovascular dysfunction during sepsis: Role of posttranslational modifications (PTMs)

Human sepsis is the result of a multifaceted pathological process causing marked dysregulation of cardiovascular responses. A more sophisticated understanding of the pathogenesis of sepsis is certainly prerequisite. Evidence from studies provide further insight into the role of inducible nitric oxide synthase (iNOS) isoform. Results on inhibition of iNOS in sepsis models remain inconclusive. Concern has been devoted to improving our knowledge and understanding of the role of iNOS. The aim of this review is to define the role of iNOS in redox homeostasis disturbance, the detailed mechanisms linking iNOS and posttranslational modifications (PTMs) to cardiovascular dysfunctions, and their future implications in sepsis settings. Many questions related to the iNOS and PTMs still remain open, and much more work is needed on this.

Involvement of protein S-nitrosylation in regulating beef apoptosis during postmortem aging

This study was the first attempt to explore the effect of protein S-nitrosylation on the progress of apoptosis in postmortem beef semimembranosus muscle (SM). Five beef SM were incubated with S-nitrosoglutathione (GSNO, nitric oxide donor), control, or Nω-nitro-l-arginine methyl ester hydrochloride (l-NAME, nitric oxide synthase inhibitor). Results suggest that compared to the control, more chromatin condensation, nucleusfragmentation, apoptoticbody formation, and mitochondrialswelling were observed in the l-NAME group while these apoptosis-related morphological changes were retarded in the GSNO group. Notably, there were fewer apoptotic nuclei in the GSNO group and more apoptotic nuclei in the l-NAME group compared to the control (P < 0.05). Additionally, caspase-3 and -9 activities and caspase-3 activation were greatly decreased by GSNO treatment and increased by l-NAME treatment (P < 0.05). The morphological and biochemical results indicate that protein S-nitrosylation could play a negative regulatory role in beef apoptosis during postmortem aging.

Edaravone inhibits procaspase-3 denitrosylation and activation through FasL-Trx2 pathway in KA-induced seizure

Previous studies have demonstrated that excessive free radicals play an essential role in the initiation and progression of epilepsy and that a novel exogenous free radical scavenger edaravone (Ed) exerts some neuroprotective effects on seizure-induced neuronal damage. The purpose of this study was to elucidate the possible molecular mechanisms of Ed associated with procaspase-3 denitrosylation and activation through the FasL-Trx2 pathway in seizures rats. In this study, we investigated the effects of Ed on the regulation of the combination of Fas ligand/Fas receptor and the major components of the death-inducing signaling complex (DISC) in the hippocampus of kainic acid (KA)-treated Sprague Dawley (SD) rats. Treatment with Ed can attenuate the increased expression of FasL induced by KA and prevent procaspase-3 denitrosylation and activation via suppression of the FasL-Trx2 signaling pathway, which alleviates the neuronal damage in seizures. These results provide experimental evidence that Ed functions by preventing the denitrosylation and activation of procaspase-3 and that Ed acts as a therapeutic option for epilepsy.

Phosphoinositide specific phospholipase Cγ1 inhibition-driven autophagy caused cell death in human lung adenocarcinoma A549 cells in vivo and in vitro

Our previous studies indicated that phosphoinositide specific phospholipase Cγ1 (PLCγ1) was involved in autophagy induction in colon and hepatic carcinoma cells. However, whether and how PLCγ1 regulation in human lung adenocarcinoma is linked to autophagy remains unclear. Here, we assessed the protein expression of PLCγ1 in human lung adenocarcinoma tissue using immunohistochemistry assay and the relationship between PLCG1 and autophagy in The Cancer Genome Atlas Network (TCGA) using Spearman correlation analysis and GSEA software. Furthermore, the interaction between PLCγ1 and autophagy-related signal molecules was investigated in human lung adenocarcinoma A549 cells treated with different inhibitors or transduction with lentivirus-mediated PLCγ1 gene short-hairpin RNA (shRNA) vectors using MTT, clonogenicity, Transwell migration, RT-PCR, Caspase-3, mitochondrial transmembrane potential, and western blotting assays, as well as transmission electron microscope technique. Additionally, the effect of shRNA/PLCγ1 alone or combined with autophagic activator Lithium Chloride (LiCl) on tumor growth and metastasis was measured using immunohistochemistry and assays in A549 xenograft nude mouse model. The results showed that increased PLCγ1 expression occurred frequently in human lung adenocarcinoma tissue with higher grades of T in TNM staging classification. PLCγ1 significantly enriched in autophagic process and regulation, which negatively regulating autophagy was enriched in higher expression of PLCγ1. PLCγ1 inhibition partially reduced cell proliferation and migration of A549 cells, with an increased autophagic flux involving alterations of AMPKα, mTOR, and ERK levels. However, PLCγ1 inhibition-driven autophagy led to cell death without depending on Caspase-3 and RIP1. Additionally, the abrogation of PLCγ1 signaling by shRNA and combination with autophagic activator LiCl could efficaciously suppress tumor growth and metastasis in A549 xenograft nude mice, in combination with a decrease in P62 level. These findings collectively suggest that reduction of cell proliferation and migration by PLCγ1 inhibition could be partially attributed to PLCγ1 inhibition-driven autophagic cell death (ACD). It highlights the potential role of a combination between targeting PLCγ1 and autophagy pathway in anti-tumor therapy, which may be an efficacious new strategy to overcome the autophagy addition of tumor and acquired resistance to current therapy.

Spotlight on ROS and β3-Adrenoreceptors Fighting in Cancer Cells

The role of ROS and RNS is a long-standing debate in cancer. Increasing the concentration of ROS reaching the toxic threshold can be an effective strategy for the reduction of tumor cell viability. On the other hand, cancer cells, by maintaining intracellular ROS concentration at an intermediate level called “mild oxidative stress,” promote the activation of signaling that favors tumor progression by increasing cell viability and dangerous tumor phenotype. Many chemotherapeutic treatments induce cell death by rising intracellular ROS concentration. The persistent drug stimulation leads tumor cells to simulate a process called hormesis by which cancer cells exhibit a biphasic response to exposure to drugs used. After a first strong response to a low dose of chemotherapeutic agent, cancer cells start to decrease the response even if high doses of drugs were used. In this framework, β3-adrenoreceptors (β3-ARs) fit with an emerging antioxidant role in cancer. β3-ARs are involved in tumor proliferation, angiogenesis, metastasis, and immune tolerance. Its inhibition, by the selective β3-ARs antagonist (SR59230A), leads cancer cells to increase ROS concentration thus inducing cell death and to decrease NO levels thus inhibiting angiogenesis. In this review, we report an overview on reactive oxygen biology in cancer cells focusing on β3-ARs as new players in the antioxidant pathway.

Procaspase-3 Overexpression in Cancer: A Paradoxical Observation with Therapeutic Potential

Many anticancer strategies rely on the promotion of apoptosis in cancer cells as a means to shrink tumors. Crucial for apoptotic function are executioner caspases, most notably caspase-3, that proteolyze a variety of proteins, inducing cell death. Paradoxically, overexpression of procaspase-3 (PC-3), the low-activity zymogen precursor to caspase-3, has been reported in a variety of cancer types. Until recently, this counterintuitive overexpression of a pro-apoptotic protein in cancer has been puzzling. Recent studies suggest subapoptotic caspase-3 activity may promote oncogenic transformation, a possible explanation for the enigmatic overexpression of PC-3. Herein, the overexpression of PC-3 in cancer and its mechanistic basis is reviewed; collectively, the data suggest the potential for exploitation of PC-3 overexpression with PC-3 activators as a targeted anticancer strategy.

Breast cancer drugs perturb fundamental vascular functions of endothelial cells by attenuating protein S-nitrosylation

Cardiovascular side effects of broadly used chemotherapeutic drugs such as Tamoxifen citrate (TC), Capecitabine (CP) and Epirubicin (EP) among cancer survivors are well established. Nitric oxide (NO) is known to protect cardiovascular tissues under conditions of stress. NO can act through cyclic guanosine monophosphate (cGMP)-dependent and -independent pathways. Particularly, the S-nitrosylation of SH-groups in a protein by NO falls under cGMP-independent effects of NO. TC, CP, and EP are hypothesized as interfering with cellular protein S-nitrosylation, which, in turn, may lead to endothelial dysfunctions. The results show that all three drugs attenuate nitrosylated proteins in endothelial cells. A significant reduction in endogenous S-nitrosylated proteins was revealed by Saville-Griess assay, immunofluorescence and western blot. Incubation with the drugs causes a reduction in endothelial migration, vasodilation and tube formation, while the addition of S-nitrosoglutathione (GSNO) has a reversal of this effect. In conclusion, results indicate the possibility of decreased cellular nitrosothiols as being one of the reasons for endothelial dysfunctions under TC, CP and EP treatment. Identification of the down-regulated S-nitrosylated proteins so as to correlate their implications on fundamental vascular functions could be an interesting phenomenon.

Major obstacles to doxorubicin therapy: Cardiotoxicity and drug resistance

Background

Doxorubicin is one of the most commonly prescribed and time-tested anticancer drugs. Although being considered as a first line drug in different types of cancers, the two main obstacles to doxorubicin therapy are drug-induced cardiotoxicity and drug resistance.

Method

The study utilizes systemic reviews on publications of previous studies obtained from scholarly journal databases including PubMed, Medline, Ebsco Host, Google Scholar, and Cochrane. The study utilizes secondary information obtained from health organizations using filters and keywords to sustain information relevancy. The study utilizes information retrieved from studies captured in the peer-reviewed journals on “doxorubicin-induced cardiotoxicity” and “doxorubicin resistance.”

Discussion and results

The exact mechanisms of cardiotoxicity are not known; various hypotheses are studied. Doxorubicin can lead to free radical generation in various ways. The commonly proposed underlying mechanisms promoting doxorubicin resistance are the expression of multidrug resistance proteins as well as other causes.

Conclusion

In this review, we have described the major obstacles to doxorubicin therapy, doxorubicin-induced cardiotoxicity as well as the mechanisms of cancer drug resistance and in following the treatment failures.

Cardioprotective effects of Prolame and SNAP are related with nitric oxide production and with diminution of caspases and calpain-1 activities in reperfused rat hearts

Cardiac tissue undergoes changes during ischemia-reperfusion (I-R) that compromise its normal function. Cell death is one of the consequences of such damage, as well as diminution in nitric oxide (NO) content. This signaling molecule regulates the function of the cardiovascular system through dependent and independent effects of cyclic guanosine monophosphate (cGMP). The independent cGMP pathway involves post-translational modification of proteins by S-nitrosylation. Studies in vitro have shown that NO inhibits the activity of caspases and calpains through S-nitrosylation of a cysteine located in their catalytic site, so we propose to elucidate if the regulatory mechanisms of NO are related with changes in S-nitrosylation of cell death proteins in the ischemic-reperfused myocardium. We used two compounds that increase the levels of NO by different mechanisms: Prolame, an amino-estrogenic compound with antiplatelet and anticoagulant effects that induces the increase of NO levels in vivo by activating the endothelial nitric oxide synthase (eNOS) and that has not been tested as a potential inhibitor of apoptosis. On the other hand, S-Nitroso-N-acetylpenicillamine (SNAP), a synthetic NO donor that has been shown to decrease cell death after inducing hypoxia-reoxygenation in cell cultures. Main experimental groups were Control, I-R, I-R+Prolame and I-R+SNAP. Additional groups were used to evaluate the NO action pathways. Contractile function represented as heart rate and ventricular pressure was evaluated in a Langendorff system. Infarct size was measured with 2,3,5-triphenyltetrazolium chloride stain. NO content was determined indirectly by measuring nitrite levels with the Griess reaction and cGMP content was measured by Enzyme-Linked ImmunoSorbent Assay. DNA integrity was evaluated by DNA laddering visualized on an agarose gel and by Terminal deoxynucleotidyl transferase dUTP Nick-End Labeling assay. Activities of caspase-3, caspase-8, caspase-9 and calpain-1 were evaluated spectrophotometrically and the content of caspase-3 and calpain-1 by western blot. S-nitrosylation of caspase-3 and calpain-1 was evaluated by labeling S-nitrosylated cysteines. Our results show that both Prolame and SNAP increased NO content and improved functional recovery in post-ischemic hearts. cGMP-dependent and S-nitrosylation pathways were activated in both groups, but the cGMP-independent pathway was preferentially activated by SNAP, which induced higher levels of NO than Prolame. Although SNAP effectively diminished the activity of all the proteases, a correlative link between the activity of these proteases and S-nitrosylation was not fully established.

Cellular demolition: Proteins as molecular players of programmed cell death

Apoptosis, a well-characterized and regulated cell death programme in eukaryotes plays a fundamental role in developing or later-life periods to dispose of unwanted cells to maintain typical tissue architecture, homeostasis in a spatiotemporal manner. This silent cellular death occurs without affecting any neighboring cells/tissue and avoids triggering of immunological response. Furthermore, diminished forms of apoptosis result in cancer and autoimmune diseases, whereas unregulated apoptosis may also lead to the development of a myriad of neurodegenerative diseases. Unraveling the mechanistic events in depth will provide new insights into understanding physiological control of apoptosis, pathological consequences of abnormal apoptosis and development of novel therapeutics for diseases. Here we provide a brief overview of molecular players of programmed cell death with discussion on the role of caspases, modifications, ubiquitylation in apoptosis, removal of the apoptotic body and its relevance to diseases.

Blockade of L-type Ca2+ channel attenuates doxorubicin-induced cardiomyopathy via suppression of CaMKII-NF-κB pathway

Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) and nuclear factor-kappa B (NF-κB) play crucial roles in pathogenesis of doxorubicin (DOX)-induced cardiomyopathy. Their activities are regulated by intracellular Ca²⁺. We hypothesized that blockade of L-type Ca²⁺ channel (LTCC) could attenuate DOX-induced cardiomyopathy by regulating CaMKII and NF-κB. DOX activated CaMKII and NF-κB through their phosphorylation and increased cleaved caspase 3 in cardiomyocytes. Pharmacological blockade or gene knockdown of LTCC by nifedipine or small interfering RNA, respectively, suppressed DOX-induced phosphorylation of CaMKII and NF-κB and apoptosis in cardiomyocytes, accompanied by decreasing intracellular Ca²⁺ concentration. Autocamtide 2-related inhibitory peptide (AIP), a selective CaMKII inhibitor, inhibited DOX-induced phosphorylation of NF-κB and cardiomyocyte apoptosis. Inhibition of NF-κB activity by ammonium pyrrolidinedithiocarbamate (PDTC) suppressed DOX-induced cardiomyocyte apoptosis. DOX-treatment (18 mg/kg via intravenous 3 injections over 1 week) increased phosphorylation of CaMKII and NF-κB in mouse hearts. Nifedipine (10 mg/kg/day) significantly suppressed DOX-induced phosphorylation of CaMKII and NF-κB and cardiomyocyte injury and apoptosis in mouse hearts. Moreover, it attenuated DOX-induced left ventricular dysfunction and dilatation. Our findings suggest that blockade of LTCC attenuates DOX-induced cardiomyocyte apoptosis via suppressing intracellular Ca²⁺ elevation and activation of CaMKII-NF-κB pathway. LTCC blockers might be potential therapeutic agents against DOX-induced cardiomyopathy.

Hydrogen sulfide-mediated regulation of cell death signaling ameliorates adverse cardiac remodeling and diabetic cardiomyopathy

The death of cardiomyocytes is a precursor for the cascade of hypertrophic and fibrotic remodeling that leads to cardiomyopathy. In diabetes mellitus (DM), the metabolic environment of hyperglycemia, hyperlipidemia, and oxidative stress causes cardiomyocyte cell death, leading to diabetic cardiomyopathy (DMCM), an independent cause of heart failure. Understanding the roles of the cell death signaling pathways involved in the development of cardiomyopathies is crucial to the discovery of novel targeted therapeutics and biomarkers for DMCM. Recent evidence suggests that hydrogen sulfide (H2S), an endogenous gaseous molecule, has cardioprotective effects against cell death. However, very little is known about signaling by which H2S and its downstream targets regulate myocardial cell death in the DM heart. This review focuses on H2S in the signaling of apoptotic, autophagic, necroptotic, and pyroptotic cell death in DMCM and other cardiomyopathies, abnormalities in H2S synthesis in DM, and potential H2S-based therapeutic strategies to mitigate myocardial cell death to ameliorate DMCM.

Protective effect of nebivolol on doxorubicin-induced cardiotoxicity in rats

INTRODUCTION

The cardiotoxicity of doxorubicin is incompletely understood. We investigated the prophylactic effect of nebivolol on doxorubicin-induced cardiac toxicity.

MATERIAL AND METHODS

Thirty rats were divided into a control group, doxorubicin-treated group and nebivolol + doxorubicin-treated group. The specimens were examined using H + E and Masson's trichrome, caspase 3, endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS) and tumor necrosis factor factor-α (TNF-α). The mean area percentage of collagen fiber content, caspase-3, eNOS, iNOS and TNF-α immunoactivities was measured.

RESULTS

The doxorubicin-treated group showed marked myocyte distortion and fragmentation, congestion and cytoplasmic lysis in most fibers. These changes were less intense in the nebivolol-treated group. The mean area percentage of collagen fiber in the nebivolol-treated group was non-significantly smaller (p = 0.07) than that in the doxorubicin-treated group. The expression of caspase-3 (p = 0.03), eNOS (p ≤ 0.001), iNOS (p < 0.001) and TNF-α (p = 0.003) immunoreactivity was improved in the nebivolol-treated group.

CONCLUSIONS

Nebivolol exerted a significant protective effect from doxorubicin toxicity. The protective effect appears to be mediated mainly through caspase-3, eNOS, iNOS and TNF-α modulation.

Tetrahydrobiopterin modulates ubiquitin conjugation to UBC13/UBE2N and proteasome activity by S-nitrosation

Nitric Oxide (NO) is an intracellular signalling mediator, which affects many biological processes via the posttranslational modification of proteins through S-nitrosation. The availability of NO and NOS-derived reactive oxygen species (ROS) from enzymatic uncoupling are determined by the NO synthase cofactor Tetrahydrobiopterin (BH4). Here, using a global proteomics "biotin-switch" approach, we identified components of the ubiquitin-proteasome system to be altered via BH4-dependent NO signalling by protein S-nitrosation. We show S-nitrosation of ubiquitin conjugating E2 enzymes, in particular the catalytic residue C87 of UBC13/UBE2N, leading to impaired polyubiquitylation by interfering with the formation of UBC13~Ub thioester intermediates. In addition, proteasome cleavage activity in cells also seems to be altered by S-nitrosation, correlating with the modification of cysteine residues within the 19S regulatory particle and catalytic subunits of the 20S complex. Our results highlight the widespread impact of BH4 on downstream cellular signalling as evidenced by the effect of a perturbed BH4-dependent NO-Redox balance on critical processes within the ubiquitin-proteasome system (UPS). These studies thereby uncover a novel aspect of NO associated modulation of cellular homeostasis.

Src kinase activation by nitric oxide promotes resistance to anoikis in tumour cell lines

Tumour progression involves the establishment of tumour metastases at distant sites. Resistance to anoikis, a form of cell death that occurs when cells lose contact with the extracellular matrix and with neighbouring cells, is essential for metastases. NO has been associated with anoikis. NO treated HeLa cells and murine melanoma cells in suspension triggered a nitric oxide (NO)-Src kinase signalling circuitry that enabled resistance to anoikis. Two NO donors, sodium nitroprusside (SNP) (500 µM) and DETANO (125 µM), protected against cell death derived from detachment of a growth permissive surface (experimental anoikis). Under conditions of NO-mediated Src activation the following were observed: (a) down-regulation of the pro-apoptotic proteins Bim and cleaved caspase-3 and the cell surface protein, E-cadherin, (b) up-regulation of caveolin-1, and (c) the dissociation of cell aggregates formed when cells are detached from a growth permissive surface. Efficiency of reattachment of tumour cells in suspension and treated with different concentrations of an NO donor, was dependent on the NO concentration. These findings indicate that NO-activated Src kinase triggers a signalling circuitry that provides resistance to anoikis, and allows for metastases.

Effects of ERK1/2 S-nitrosylation on ERK1/2 phosphorylation and cell survival in glioma cells

Aberrant activation of extracellular signal-regulated kinase 1/2 (ERK1/2) by phosphorylation modification can trigger tumor cell development in glioma. S-nitrosylation, which refers to the covalent addition of a nitric oxide (NO) group to a cysteine (Cys) thiol, is an important post-translational modification that occurs on numerous cancer-associated proteins. Protein S-nitrosylation can increase or decrease protein activity and stability, and subsequent signal transduction and cellular processes. However, the association between ERK1/2 S-nitrosylation and ERK1/2 phosphorylation, and the effects of ERK1 S-nitrosylation on glioma cell survival are currently unknown. U251 glioma cells were treated with NO donors sodium nitroprusside (SNP) or S-nitrosoglutathione (GSNO). CCK8 assay was used to assess the cell viability. NO levels in the medium were detected by Griess assay. Western blot analysis and biotin switch assay were employed to detect the ERK1/2 phosphorylation and S-nitrosylation. ERK1 wild-type and mutant plasmids were constructed, and used to transfect the U251 cells. Caspase-3 western blot analysis and flow cytometry were employed to assess cell apoptosis. The present study demonstrated that treatment with the NO donors SNP or GSNO led to an increase in ERK1/2 S-nitrosylation, and a reduction in ERK1/2 phosphorylation, which was accompanied by growth inhibition of U251 glioma cells. Mutational analysis demonstrated that Cys¹⁸³ was vital for S-nitrosylation of ERK1, and that preventing ERK1 S-nitrosylation by replacing Cys¹⁸³ with alanine partially reversed GSNO-induced cell apoptosis, and reductions in cell viability and ERK1/2 phosphorylation. In addition, increased ERK1/2 phosphorylation was associated with decreased ERK1/2 S-nitrosylation in human glioma tissues. These findings identified the relationship between ERK1/2 S-nitrosylation and phosphorylation in vitro and in vivo, and revealed a novel mechanism of ERK1/2 underlying tumor cell development and apoptotic resistance of glioma.

Caspase signaling, a conserved inductive cue for metazoan cell differentiation

Caspase signaling pathways were originally discovered as conveyors of programmed cell death, yet a compendium of research over the past two decades have demonstrated that these same conduits have a plethora of physiologic functions. Arguably the most extensive non-death activity that has been attributed to this protease clade is the capacity to induce cell differentiation. Caspase control of differentiation is conserved across diverse metazoan organisms from flies to humans, suggesting an ancient origin for this form of cell fate control. Here we discuss the mechanisms by which caspase enzymes manage differentiation, the targeted substrates that may be common across cell lineages, and the countervailing signals that may be essential for these proteases to 'execute' this non-death cell fate.

Naringin protects myocardial cells from doxorubicin‑induced apoptosis partially by inhibiting the p38MAPK pathway

Doxorubicin (DOX) has been widely used to treat cancers as a first-line antitumor drug. However, it causes severe, irreversible, dose-dependent cardiotoxicity. To evaluate the protective effects of naringin (NRG) on cardiotoxicity, the authors investigated the molecular mechanism of the p38MAPK signaling pathway. H9c2 cells were treated for 24 h by using 5 µmol/l DOX without or with being pretreated by 1 µM NRG for 150 min or by 3 µM SB203580 for 60 min. Cell viability was detected by cell counting kit-8 assay. Intracellular reactive oxygen species (ROS) levels were detected based on the oxidative conversion of 2′,7′-dichlorfluorescein-diacetate (cell-permeable) to dichlorofluorescein (fluorescent). The expression of p38MAPK was determined by western blotting. The expression level of p-p38MAPK in H9c2 cells, which was significantly increased by exposure to 5 µM DOX for 60 min (P<0.01), was significantly decreased by pretreatment with 1 µM NRG for 150 min beforehand (P<0.01). The viability of H9c2 cells pretreated for 150 min with 1 µM NRG was significantly enhanced compared with that using DOX directly (P<0.01). Intracellular ROS levels were significantly reduced by being pretreated with 1 µM NRG for 150 min or with 3 µM SB203580 for 60 min before the cells were exposed to 5 µM DOX. Collectively, NRG protected H9c2 cells against the cardiotoxicity induced by DOX through suppressing the expression and activity of the p38MAPK pathway. The findings provided valuable evidence for the possible use of NRG to relieve DOX-induced cardiotoxicity.

How widespread is stable protein S-nitrosylation as an end-effector of protein regulation?

Over the last 25 years protein S-nitrosylation, also known more correctly as S-nitrosation, has been progressively implicated in virtually every nitric oxide-regulated process within the cardiovascular system. The current, widely-held paradigm is that S-nitrosylation plays an equivalent role as phosphorylation, providing a stable and controllable post-translational modification that directly regulates end-effector target proteins to elicit biological responses. However, this concept largely ignores the intrinsic instability of the nitrosothiol bond, which rapidly reacts with typically abundant thiol-containing molecules to generate more stable disulfide bonds. These protein disulfides, formed via a nitrosothiol intermediate redox state, are rationally anticipated to be the predominant end-effector modification that mediates functional alterations when cells encounter nitrosative stimuli. In this review we present evidence and explain our reasoning for arriving at this conclusion that may be controversial to some researchers in the field.

Antioxidant and antiapoptotic effects of sea cucumber and valsartan against doxorubicin-induced cardiotoxicity in rats: The role of low dose gamma irradiation

Doxorubicin (DOX) is a highly effective antineoplastic drug; however, the clinical use of DOX is limited by its dose dependent cardiotoxicity. This study was conducted to evaluate the cardioprotective effect of sea cucumber and valsartan against DOX-induced cardiotoxicity in rats. Also, the role of exposure to low dose γ radiation (LDR) on each of them was investigated, since LDR could suppress various reactive oxygen species-related diseases. Rats received DOX (2.5mg/kg, ip) in six equal injections over a period of 2weeks, sea cucumber (14.4mg/kg, p.o) and valsartan (30mg/kg, p.o) for 8 successive weeks. Exposure to LDR (0.5Gy) was performed one day prior to DOX. Results revealed that DOX administration elevated serum levels of aspartate aminotransferase (AST), lactate dehydrogenase (LDH), creatine kinase (CK-MB) and troponin-I as well as increased cardiac lipid peroxide content and myeloperoxidase (MPO) activity. Additionally, it increased cardiac expressions of iNOS and caspase-3, accompanied by reduction in cardiac total protein and glutathione (GSH) contents. Treatment with sea cucumber or valsartan improved the cardiotoxicity of DOX. Their adjuvant therapy with LDR offers an additional benefit to the cardioprotection of the therapeutic drugs. These results confirmed by histopathological examination. In conclusion, sea cucumber and valsartan alone or combined with LDR attenuated DOX-induced cardiotoxicity via their antioxidant and anti-apoptotic activities and thus might be useful in the treatment of human patients under doxorubicin chemotherapy.

Post-translational Modification of Caspases: The Other Side of Apoptosis Regulation

Apoptosis is a crucial program of cell death that controls development and homeostasis of multicellular organisms. The main initiators and executors of this process are the Cysteine-dependent ASPartate proteASES - caspases. A number of regulatory circuits tightly control caspase processing and activity. One of the most important, yet, at the same time still poorly understood control mechanisms of activation of caspases involves their post-translational modifications. The addition and/or removal of chemical groups drastically alters the catalytic activity of caspases or stimulates their nonapoptotic functions. In this review, we will describe and discuss the roles of key caspase modifications such as phosphorylation, ubiquitination, nitrosylation, glutathionylation, SUMOylation, and acetylation in the regulation of apoptotic cell death and cell survival.

Role of nitric oxide in liver transplantation: Should it be routinely used?

Ischemia-reperfusion injury (IRI) continues to be a major contributor to graft dysfunction, thus supporting the need for therapeutic strategies focused on minimizing organ damage especially with growing numbers of extended criteria grafts being utilized which are more vulnerable to cold and warm ischemia. Nitric oxide (NO·) is highly reactive gaseous molecule found in air and regarded as a pollutant. Not surprising, it is extremely bioactive, and has been demonstrated to play major roles in vascular homeostasis, neurotransmission, and host defense inflammatory reactions. Under conditions of ischemia, NO· has consistently been demonstrated to enhance microcirculatory vasorelaxation and mitigate pro-inflammatory responses, making it an excellent strategy for patients undergoing organ transplantation. Clinical studies designed to test this hypothesis have yielded very promising results that includes reduced hepatocellular injury and enhanced graft recovery without any identifiable complications. By what means NO· facilitates extra-pulmonary actions is up for debate and speculation. The general premise is that they are NO· containing intermediates in the circulation, that ultimately mediate either direct or indirect effects. A plethora of data exists explaining how NO·-containing intermediate molecules form in the plasma as S-nitrosothiols (e.g., S-nitrosoalbumin), whereas other compelling data suggest nitrite to be a protective mediator. In this article, we discuss the use of inhaled NO· as a way to protect the donor liver graft against IRI in patients undergoing liver transplantation.

S-nitrosylation of the Mitochondrial Chaperone TRAP1 Sensitizes Hepatocellular Carcinoma Cells to Inhibitors of Succinate Dehydrogenase

S-nitrosoglutathione reductase (GSNOR) represents the best-documented denitrosylase implicated in regulating the levels of proteins posttranslationally modified by nitric oxide on cysteine residues by S-nitrosylation. GSNOR controls a diverse array of physiologic functions, including cellular growth and differentiation, inflammation, and metabolism. Chromosomal deletion of GSNOR results in pathologic protein S-nitrosylation that is implicated in human hepatocellular carcinoma (HCC). Here we identify a metabolic hallmark of aberrant S-nitrosylation in HCC and exploit it for therapeutic gain. We find that hepatocyte GSNOR deficiency is characterized by mitochondrial alteration and by marked increases in succinate dehydrogenase (SDH) levels and activity. We find that this depends on the selective S-nitrosylation of Cys(501) in the mitochondrial chaperone TRAP1, which mediates its degradation. As a result, GSNOR-deficient cells and tumors are highly sensitive to SDH inhibition, namely to α-tocopheryl succinate, an SDH-targeting molecule that induced RIP1/PARP1-mediated necroptosis and inhibited tumor growth. Our work provides a specific molecular signature of aberrant S-nitrosylation in HCC, a novel molecular target in SDH, and a first-in-class therapy to treat the disease. Cancer Res; 76(14); 4170-82. ©2016 AACR.

C57BL/6N Mice Are More Resistant to Ehrlich Ascites Tumors Than C57BL/6J Mice: The Role of Macrophage Nitric Oxide

Background

Effectiveness of the immune defense formed by the genotype often determines the predisposition to cancer. Nitric oxide (NO) produced by macrophages is an important element in this defense.

Material/Methods

We hypothesized that genetic characteristics of NO generation systems can predetermine the vulnerability to tumor development. The study was conducted on mice of 2 genetic substrains – C57BL/6J and C57BL/6N – with Ehrlich ascites carcinoma (EAC). NO production in the tumor was changed using ITU, an iNOS inhibitor; c-PTIO, a NO scavenger; and SNP, a NO donor. Macrophage NO production was estimated by nitrite concentration in the culture medium. iNOS content was measured by Western blot analysis. Macrophage phenotype was determined by changes in NO production, iNOS level, and CD markers of the phenotype.

Results

The lifespan of C57BL/6N mice (n=10) with EAC was 25% longer (p<0.01) than in C57BL/6J mice (n=10). Decreased NO production 23% reduced the survival duration of C57BL/6N mice (p<0.05), which were more resistant to tumors. Elevated NO production 26% increased the survival duration of C57BL/6J mice (p<0.05), which were more susceptible to EAC. Both the NO production and the iNOS level were 1.5 times higher in C57BL/6N than in C57BL/6J mice (p<0.01). CD markers confirmed that C57BL/6N macrophages had the M1 and C57BL/6J macrophages had the M2 phenotype.

Conclusions

The vulnerability to the tumor development can be predetermined by genetic characteristics of the NO generation system in macrophages. The important role of NO in anti-EAC immunity should be taken into account in elaboration of new antitumor therapies.

Macrophages Reprogrammed In Vitro Towards the M1 Phenotype and Activated with LPS Extend Lifespan of Mice with Ehrlich Ascites Carcinoma

Background

The majority of tumors trigger macrophage reprogramming from an anti-tumor M1 phenotype towards a pro-tumor M2 phenotype. The M2 phenotype promotes tumor growth. We hypothesized that increasing the number of M1 macrophages in a tumor would limit carcinogenesis and extend the lifespan of the tumor host. The aim of this study was to verify this hypothesis in Ehrlich ascites carcinoma (EAC). The objectives were to evaluate effects of 1) EAC on a macrophage phenotype and NO-producing macrophage activity in vivo; 2) ascitic fluid from mice with EAC on a macrophage phenotype and NO-producing macrophage activity in vitro; and 3) in vitro reprogrammed M1 macrophages on lifespan of mice with EAC.

Material/Methods

The study was conducted using C57BL/6J mice.

Results

Concentration of nitrite, a stable NO metabolite and an index of NO production, was measured spectrophotometrically. Shifts of macrophage phenotype were assessed by changes in NO production as well as by amounts of CD80, a marker of M1 phenotype, and CD206, a marker of M2 phenotype. The CD markers were measured by flow cytometry. Macrophages were reprogrammed towards the M1 phenotype using two reprogramming factors: 0% FBS and 20 ng/ml IFN-γ. The study results showed that 1) EAC inhibited the macrophage NO production in vivo and reprogrammed macrophages towards the M2 phenotype; 2) ascitic fluid of mice with EAC inhibited the macrophage NO production in vitro and reprogrammed macrophages towards the M2 phenotype; and 3) injection of in vitro reprogrammed M1 macrophages into mice with EAC significantly increased the lifespan of mice.

Conclusions

These findings suggest that promising biotechnologies for restriction of tumor growth could be developed based on the in vitro macrophage reprogramming.

Nitrosothiol signaling and protein nitrosation in cell death

Nitric oxide, a reactive free radical, is an important signaling molecule that can lead to a plethora of cellular effects affecting homeostasis. A well-established mechanism by which NO manifests its effect on cellular functions is the post-translational chemical modification of cysteine thiols in substrate proteins by a process known as S-nitrosation. Studies that investigate regulation of cellular functions through NO have increasingly established S-nitrosation as the primary modulatory mechanism in their respective systems. There has been a substantial increase in the number of reports citing various candidate proteins undergoing S-nitrosation, which affects cell-death and -survival pathways in a number of tissues including heart, lung, brain and blood. With an exponentially growing list of proteins being identified as substrates for S-nitrosation, it is important to assimilate this information in different cell/tissue systems in order to gain an overall view of protein regulation of both individual proteins and a class of protein substrates. This will allow for broad mapping of proteins as a function of S-nitrosation, and help delineate their global effects on pathophysiological responses including cell death and survival. This information will not only provide a much better understanding of overall functional relevance of NO in the context of various disease states, it will also facilitate the generation of novel therapeutics to combat specific diseases that are driven by NO-mediated S-nitrosation.

Nitric oxide donor NOC-5 increases XIAP and Aven level in Jurkat cells

Mitochondrial permeabilisation after NO donor application did not activate caspase-9. We have studied the X-linked apoptosis inhibitor (XIAP) and Aven protein content in NO-treated Jurkat cells. The level of both proteins increased in NO-treated cells. Thus the increase in XIAP and Aven content could be the cause of the lack of caspase-9 activity after mitochondrial permeabilisation in NO-treated Jurkat cells.

Mass spectrometry-based quantitative proteomics for dissecting multiplexed redox cysteine modifications in nitric oxide-protected cardiomyocyte under hypoxia

AIMS

Distinctive states of redox-dependent cysteine (Cys) modifications are known to regulate signaling homeostasis under various pathophysiological conditions, including myocardial injury or protection in response to ischemic stress. Recent evidence further implicates a dynamic interplay among these modified forms following changes in cellular redox environment. However, a precise delineation of multiplexed Cys modifications in a cellular context remains technically challenging. To this end, we have now developed a mass spectrometry (MS)-based quantitative approach using a set of novel iodoacetyl-based Cys-reactive isobaric tags (irreversible isobaric iodoacetyl Cys-reactive tandem mass tag [iodoTMT]) endowed with unique irreversible Cys-reactivities.

RESULTS

We have established a sequential iodoTMT-switch procedure coupled with efficient immunoenrichment and advanced shotgun liquid chromatography-MS/MS analysis. This workflow allows us to differentially quantify the multiple redox-modified forms of a Cys site in the original cellular context. In one single analysis, we have identified over 260 Cys sites showing quantitative differences in multiplexed redox modifications from the total lysates of H9c2 cardiomyocytes experiencing hypoxia in the absence and presence of S-nitrosoglutathione (GSNO), indicative of a distinct pattern of individual susceptibility to S-nitrosylation or S-glutathionylation. Among those most significantly affected are proteins functionally implicated in hypoxic damage from which we showed that GSNO would protect.

INNOVATION

We demonstrate for the first time how quantitative analysis of various Cys-redox modifications occurring in biological samples can be performed precisely and simultaneously at proteomic levels.

CONCLUSION

We have not only developed a new approach to map global Cys-redoxomic regulation in vivo, but also provided new evidences implicating Cys-redox modifications of key molecules in NO-mediated ischemic cardioprotection.

S-nitrosylation of ERK inhibits ERK phosphorylation and induces apoptosis

Extracellular signal-regulated kinase (ERK) belongs to the mitogen-activated protein kinases (MAPK) superfamily. Aberrant upregulation and activation of ERK cascades may often lead to tumor cell development. However, how ERK is involved in tumor progression is yet to be defined. In current study, we described that ERK undergoes S-nitrosylation by nitric oxide (NO). ERK S-nitrosylation inhibits its phosphorylation and triggers apoptotic program as verified by massive apoptosis in fluorescence staining. The proapoptotic effect of NO induced S-nitrosylation is reversed by NO scavenger Haemoglobin (HB). Furthermore, an S-nitrosylation dead ERK mutant C183A also demolishes the proapoptotic potential of NO and favors cell survival. Therefore, Cys¹⁸³ might be a potential S-nitrosylation site in ERK. In addition, S-nitrosylation is a general phenomenon that regulates ERK activity. These findings identify a novel link between NO-mediated S-nitrosylation and ERK regulation, which provide critical insights into the control of apoptosis and tumor development.

Protective effect of cannabidiol against cadmium hepatotoxicity in rats

The protective effect of cannabidiol, the non-psychoactive component of Cannabis sativa, against liver toxicity induced by a single dose of cadmium chloride (6.5 mgkg(-1) i.p.) was investigated in rats. Cannabidiol treatment (5 mgkg(-1)/day, i.p.) was applied for five days starting three days before cadmium administration. Cannabidiol significantly reduced serum alanine aminotransferase, and suppressed hepatic lipid peroxidation, prevented the depletion of reduced glutathione and nitric oxide, and catalase activity, and attenuated the elevation of cadmium level in the liver tissue resulted from cadmium administration. Histopathological examination showed that cadmium-induced liver tissue injury was ameliorated by cannabidiol treatment. Immunohistochemical analysis revealed that cannabidiol significantly decreased the cadmium-induced expression of tumor necrosis factor-α, cyclooxygenase-2, nuclear factor-κB, caspase-3, and caspase-9, and increased the expression of endothelial nitric oxide synthase in liver tissue. It was concluded that cannabidiol may represent a potential option to protect the liver tissue from the detrimental effects of cadmium toxicity.

Nitric oxide donors: spermine/NO and diethylenetriamine/NO induce ovarian cancer cell death and affect STAT3 and AKT signaling proteins

The important features of cancer cells are uncontrolled growth and proliferation, as well as the ability to metastasis. These features depend mainly on the constant overexpression and activity of various cell signaling proteins, such as signal transducer and activator of transcription 3 (STAT3) and serine-threonine protein kinase AKT proteins. Nitric oxide (NO) has the potential of being anti-tumoral agent, however the exact character of anti-tumoral action of NO is still a matter of debate. In our research we used two NO donors, belonging to NONOates family, with different half-life times: spermine nitric oxide complex hydrate (SPER/NO t1/2=39min) and diethylenetriamine nitric oxide adduct (DETA/NO, t1/2=20h). We evaluated the cytotoxic effect of aforementioned NO donors on SK-OV-3 and OVCAR-3 ovarian cancer cell lines, as well as their effect on posttranslational modification of STAT3 and AKT proteins in these cells. We found that both NO donors present cytotoxic activity on the cancer cell lines, mainly through the induction of apoptosis. What is more, at the high concentration and longer exposure time they were also capable of inducing late apoptosis/necrosis. Both NO donors inhibited STAT3 and AKT3 proteins phosphorylation and down regulated their cytosolic levels, with DETA/NO being stronger inhibitor. We suggests, that NO donors have the potential to act as anti-tumoral agent through inhibiting cancer cell signaling and reducing their viability.

Increased S-nitrosylation and proteasomal degradation of caspase-3 during infection contribute to the persistence of adherent invasive Escherichia coli (AIEC) in immune cells

Adherent invasive Escherichia coli (AIEC) have been implicated as a causative agent of Crohn’s disease (CD) due to their isolation from the intestines of CD sufferers and their ability to persist in macrophages inducing granulomas. The rapid intracellular multiplication of AIEC sets it apart from other enteric pathogens such as Salmonella Typhimurium which after limited replication induce programmed cell death (PCD). Understanding the response of infected cells to the increased AIEC bacterial load and associated metabolic stress may offer insights into AIEC pathogenesis and its association with CD. Here we show that AIEC persistence within macrophages and dendritic cells is facilitated by increased proteasomal degradation of caspase-3. In addition S-nitrosylation of pro- and active forms of caspase-3, which can inhibit the enzymes activity, is increased in AIEC infected macrophages. This S-nitrosylated caspase-3 was seen to accumulate upon inhibition of the proteasome indicating an additional role for S-nitrosylation in inducing caspase-3 degradation in a manner independent of ubiquitination. In addition to the autophagic genetic defects that are linked to CD, this delay in apoptosis mediated in AIEC infected cells through increased degradation of caspase-3, may be an essential factor in its prolonged persistence in CD patients.

Cellular mechanisms controlling caspase activation and function

Caspases are the primary drivers of apoptotic cell death, cleaving cellular proteins that are critical for dismantling the dying cell. Initially translated as inactive zymogenic precursors, caspases are activated in response to a variety of cell death stimuli. In addition to factors required for their direct activation (e.g., dimerizing adaptor proteins in the case of initiator caspases that lie at the apex of apoptotic signaling cascades), caspases are regulated by a variety of cellular factors in a myriad of physiological and pathological settings. For example, caspases may be modified posttranslationally (e.g., by phosphorylation or ubiquitylation) or through interaction of modulatory factors with either the zymogenic or active form of a caspase, altering its activation and/or activity. These regulatory events may inhibit or enhance enzymatic activity or may affect activity toward particular cellular substrates. Finally, there is emerging literature to suggest that caspases can participate in a variety of cellular processes unrelated to apoptotic cell death. In these settings, it is particularly important that caspases are maintained under stringent control to avoid inadvertent cell death. It is likely that continued examination of these processes will reveal new mechanisms of caspase regulation with implications well beyond control of apoptotic cell death.

Inhibition of vascular smooth muscle cell proliferation by Gentiana lutea root extracts

Gentiana lutea belonging to the Gentianaceae family of flowering plants are routinely used in traditional Serbian medicine for their beneficial gastro-intestinal and anti-inflammatory properties. The aim of the study was to determine whether aqueous root extracts of Gentiana lutea consisting of gentiopicroside, gentisin, bellidifolin-8-O-glucoside, demethylbellidifolin-8-O-glucoside, isovitexin, swertiamarin and amarogentin prevents proliferation of aortic smooth muscle cells in response to PDGF-BB. Cell proliferation and cell cycle analysis were performed based on alamar blue assay and propidium iodide labeling respectively. In primary cultures of rat aortic smooth muscle cells (RASMCs), PDGF-BB (20 ng/ml) induced a two-fold increase in cell proliferation which was significantly blocked by the root extract (1 mg/ml). The root extract also prevented the S-phase entry of synchronized cells in response to PDGF. Furthermore, PDGF-BB induced ERK1/2 activation and consequent increase in cellular nitric oxide (NO) levels were also blocked by the extract. These effects of extract were due to blockade of PDGF-BB induced expression of iNOS, cyclin D1 and proliferating cell nuclear antigen (PCNA). Docking analysis of the extract components on MEK1, the upstream ERK1/2 activating kinase using AutoDock4, indicated a likely binding of isovitexin to the inhibitor binding site of MEK1. Experiments performed with purified isovitexin demonstrated that it successfully blocks PDGF-induced ERK1/2 activation and proliferation of RASMCs in cell culture. Thus, Gentiana lutea can provide novel candidates for prevention and treatment of atherosclerosis.