Protein kinase cδ in apoptosis: a brief overview

Exacerbated interfacial impacts of nanoplastics and 6:2 chlorinated polyfluorinated ether sulfonate by natural organic matter in adult zebrafish: Evidence through histopathology, gut microbiota, and transcriptomic analysis

Nanoplastics (NPs) interact with cooccurring chemicals and natural organic matter (NOM) in the environment, forming complexes that can change their bioavailability and interfacial toxicity in aquatic organisms. This study aims to elucidate the single and combined impacts of 21-day chronic exposure to low levels of polystyrene NPs (size 80 nm) at 1 mg/L and 6:2 chlorinated polyfluorinated ether sulfonate (Cl-PFAES or F53B) at 200 μg/L in the presence and absence of NOM (humic acid-HA and bovine serum albumin-BSA at 10 mg/L) in adult zebrafish (Danio rerio). Our findings through multiple bioassays, revealed that the mixture group (M), comprising of NPs, F53B, HA, and BSA, caused a higher level of toxicity compared to the single NPs (AN), single F53B (AF), and combined NPs+F53B (ANF) groups. The mixture exposure caused the highest level of vacuolization and nuclear condensation in hepatocytes, and most of the intestinal villi were fused and highly reduced in villi length and crypt depth. Further, the T-AOC levels were significantly lower (p < 0.05), while the MDA levels in the liver and intestine were significantly higher (p < 0.05) in the M group with downregulation of nfkbiaa, while upregulation of prkcda, csf1ra, and il1b apoptosis genes in the liver. Pairwise comparison of gut microbiota showed significantly higher (p < 0.05) abundances of various genera in the M group, including Gordonia, Methylobacterium, Tundrisphaera, GKS98, Pedomicrobium, Clostridium, Candidatus and Anaerobacillus, as well as higher abundance of genera including pathogenic strains, while control group showed higher abundance of probiotic genus ZOR0006 than exposed group (p < 0.01). The transcriptomic analysis revealed highest number of DEGs in the M group (2815), followed by the AN group (506) and ANF group (206) with the activation of relaxin signaling pathway-RSP (slc9a1, slc9a2) and AMP-activated protein kinase (AMPK) pathway (plin1), and suppression of the toll-like receptor (TLR) pathway (tlr4a, tlr2, tlr1), cytokine-cytokine receptor interaction (CCRI) pathway (tnfb, il21r1, il21, ifng1), and peroxisome proliferator-activated receptors (PPAR) pathway (pfkfb3). Overall, toxicity in the M group was higher, indicating that the HA and BSA elevated the interfacial impacts of NPs and F53B in adult zebrafish after chronic environmentally relevant exposure, implying the revisitation of the critical interaction of NOM with co-occurring chemicals and associated impacts.

TLR Engagement Induces an Alternate Pathway for BCR Signaling that Results in PKCδ Phosphorylation

Recently, we reported that preexposure of B cells to IL-4 induced an alternate, signalosome-independent BCR signaling pathway leading to protein kinase C (PKC)δ phosphorylation (pTyr311), which occurs in the membrane compartment. This is considered to represent a form of receptor crosstalk and signal integration. Unlike the classical BCR signaling pathway, Lyn kinase is indispensable for BCR-induced downstream events in the alternate pathway. Our previous report that alternate BCR signaling leading to ERK phosphorylation is triggered by LPS and PAM3CSK4 (much like IL-4) raises the possibility that other signaling outcomes such as PKCδ phosphorylation might be similarly affected. To explore the range of mediators capable of producing an alternate pathway for BCR signaling, we examined PKCδ translocation and phosphorylation in LPS- and PAM3CSK4-treated B cells stimulated by anti-Ig. We found that LPS and PAM3CSK4 alter the signaling pathway used by the BCR to produce PKCδ phosphorylation. As with IL-4, elements of the signalosome are not needed for PKCδ phosphorylation when BCR triggering occurs after LPS and PAM3CSK4. However, with LPS and PAM3CSK4, anti-Ig-induced phosphorylation of PKCδ takes place in the cytosol, in contrast to the IL-4-induced alternate pathway, wherein PKCδ phosphorylation occurs in the membrane. Furthermore, the BCR signaling pathway induced by LPS and PAM3CSK4 differs from that induced by IL-4 by not requiring Lyn. Thus, an alternate, signalosome-independent BCR signaling pathway for PKCδ phosphorylation is induced by TLR agonists but differs in important ways from the alternate pathway induced by IL-4.

Sperm freezing damage: the role of regulated cell death

Substantial progress in research on sperm cryopreservation has occurred since the twentieth century, especially focusing on improving sperm freezing procedures and optimizing semen extenders. However, the cellular biological mechanisms of sperm freezing damage are still unclear, which greatly restricts the promotion and development of sperm cryopreservation. An essential component of sperm freezing damage is the occurrence of cell death. Considering the existence of multiple types of cell death pathways, this review discusses connections between characteristics of regulated cell death (e.g., apoptosis and ferroptosis), and accidental cell death (e.g., intracellular ice crystals) with sperm freezing damage and explores possible future research directions in this field.

Utility of sulfachloropyridazine in the synthesis of novel anticancer agents as antiangiogenic and apoptotic inducers

In a search for new anticancer agents with better activity and selectivity, the present work described the synthesis of several new series of sulfachloropyridazine hybrids with thiocarbamates 3a-e, thioureids 4a-h, 5a-e and 4-substituted sulfachloropyridazines 6a, b, 7a, b and 8. The synthesized compounds were screened in vitro against a panel of 60 cancer cell lines in one dose assay. The most potent derivatives 3a, 3c, 4c, 4d, 5e, 7a and 7b were tested for their antiangiogenic activity by measuring their ability to inhibit VEGFR-2. The most potent compounds in VEGFR-2 inhibitory assay were further evaluated for their ability to inhibit PDGFR. In addition, the ability of 4c compound to inhibit cell migration on HUVEC cells and cell cycle effect on UO-31 cells has been studied. The pro-apoptotic effect of compound 4c was studied by the evaluation of caspase-3, Bax and BCl-2. Alternatively, the IC50 of compounds 3a, 3c, 4c, 5e, 7a and 7b against certain human cancer cell lines were determined. Re-evaluation in combination with γ-radiation was carried out for compounds 4c, 5e and 7b to study the possible synergistic effect on cytotoxicity. Docking studies of the most active compounds were performed to give insights into the binding mode within VEGFR-2 active site.

The Role of Cdo1 in Ferroptosis and Apoptosis in Cancer

Cysteine dioxygenase type 1 (Cdo1) is a tumor suppressor gene. It regulates the metabolism of cysteine, thereby influencing the cellular antioxidative capacity. This function puts Cdo1 in a prominent position to promote ferroptosis and apoptosis. Cdo1 promotes ferroptosis mainly by decreasing the amounts of antioxidants, leading to autoperoxidation of the cell membrane through Fenton reaction. Cdo1 promotes apoptosis mainly through the product of cysteine metabolism, taurine, and low level of antioxidants. Many cancers exhibit altered function of Cdo1, underscoring its crucial role in cancer cell survival. Genetic and epigenetic alterations have been found, with methylation of Cdo1 promoter as the most common mutation. The fact that no cancer was found to be caused by altered Cdo1 function alone indicates that the tumor suppressor role of Cdo1 is mild. By compiling the current knowledge about apoptosis, ferroptosis, and the role of Cdo1, this review suggests possibilities for how the mild anticancer role of Cdo1 could be harnessed in new cancer therapies. Here, developing drugs targeting Cdo1 is considered meaningful in neoadjuvant therapies, for example, helping against the development of anti-cancer drug resistance in tumor cells.

Phosphorylation of PP2Ac by PKC is a key regulatory step in the PP2A-switch-dependent AKT dephosphorylation that leads to apoptosis

BACKGROUND

Although GqPCR activation often leads to cell survival by activating the PI3K/AKT pathway, it was previously shown that in several cell types AKT activity is reduced and leads to JNK activation and apoptosis. The mechanism of AKT inactivation in these cells involves an IGBP1-coupled PP2Ac switch that induces the dephosphorylation and inactivation of both PI3K and AKT. However, the machinery involved in the initiation of PP2A switch is not known.

METHODS

We used phospho-mass spectrometry to identify the phosphorylation site of PP2Ac, and raised specific antibodies to follow the regulation of this phosphorylation. Other phosphorylations were monitored by commercial antibodies. In addition, we used coimmunoprecipitation and proximity ligation assays to follow protein-protein interactions. Apoptosis was detected by a TUNEL assay as well as PARP1 cleavage using SDS-PAGE and Western blotting.

RESULTS

We identified Ser24 as a phosphorylation site in PP2Ac. The phosphorylation is mediated mainly by classical PKCs (PKCα and PKCβ) but not by novel PKCs (PKCδ and PKCε). By replacing the phosphorylated residue with either unphosphorylatable or phosphomimetic residues (S24A and S24E), we found that this phosphorylation event is necessary and sufficient to mediate the PP2A switch, which ultimately induces AKT inactivation, and a robust JNK-dependent apoptosis.

CONCLUSION

Our results show that the PP2A switch is induced by PKC-mediated phosphorylation of Ser24-PP2Ac and that this phosphorylation leads to apoptosis upon GqPCR induction of various cells. We propose that this mechanism may provide an unexpected way to treat some cancer types or problems in the endocrine machinery.

Comparative proteomic analysis of cerebral cortex revealed neuroprotective mechanism of esculentoside A on Alzheimer's disease

Esculentoside A (EsA), isolated from phytolacca esculenta, is a saponin showing neuroprotective effect in the mouse models of Alzheimer's disease (AD). To investigate its action target and underlying mechanism, this study used the proteomics technique of isobaric tags for relative and absolute quantification (iTRAQ) to analyze the differentially expressed proteins (DEPs) in the cerebral cortex of EsA-treated and untreated triple-transgenic 3 × Tg-AD model mice. Proteomic comparison revealed 250, 436, and 903 DEPs in three group pairs, i.e. AD/Wild-type (WT), AD+5 mg/kg EsA/AD, AD+10 mg/kg EsA/AD, respectively. Among them 28 DEPs were commonly shared by three group pairs, and 25 of them showed reversed expression levels in the diseased group under the treatment of both doses of EsA. Bioinformatics analysis revealed that these DEPs were mainly linked to metabolism, synapses, apoptosis, learning and memory. EsA treatment restored the expression of these proteins, including amyloid precursor protein (APP), cathepsin B (Cstb), 4-aminobutyrate aminotransferase (Abat), 3-phosphoinositide-dependent protein kinase-1 (PDK1), carnitine palmitoyltransferase1 (Cpt1) and synaptotagmin 17 (Syt17), thereby ameliorated the spatial learning and memory of AD mice. Collectively, this study reveals for the first time the profound effect of EsA on the cerebral cortex of AD mice, which might be a potential therapeutic agent for the treatment of AD.

A Multimodel Study of the Role of Novel PKC Isoforms in the DNA Integrity Checkpoint

The protein kinase C (PKC) family plays important regulatory roles in numerous cellular processes. Saccharomyces cerevisiae contains a single PKC, Pkc1, whereas in mammals, the PKC family comprises nine isoforms. Both Pkc1 and the novel isoform PKCδ are involved in the control of DNA integrity checkpoint activation, demonstrating that this mechanism is conserved from yeast to mammals. To explore the function of PKCδ in a non-tumor cell line, we employed CRISPR-Cas9 technology to obtain PKCδ knocked-out mouse embryonic stem cells (mESCs). This model demonstrated that the absence of PKCδ reduced the activation of the effector kinase CHK1, although it suggested that other isoform(s) might contribute to this function. Therefore, we used yeast to study the ability of each single PKC isoform to activate the DNA integrity checkpoint. Our analysis identified that PKCθ, the closest isoform to PKCδ, was also able to perform this function, although with less efficiency. Then, by generating truncated and mutant versions in key residues, we uncovered differences between the activation mechanisms of PKCδ and PKCθ and identified their essential domains. Our work strongly supports the role of PKC as a key player in the DNA integrity checkpoint pathway and highlights the advantages of combining distinct research models.

X-rays Stimulate Granular Secretions and Activate Protein Kinase C Signaling in Human Platelets

X-rays can induce morphological as well as functional changes in cells. Platelets are anuclear cellular fragments originating from megakaryocytes and are the major regulators in hemostasis and thrombosis. Platelet products are irradiated to avoid medical complications associated with platelet transfusion. So far, gamma, UV, and laser radiation have been used for this purpose. However, scientists are divided about the effects of radiation on platelet quality. The present study was designed to explore the possible effects of X-rays in washed human platelets and understand the molecular mechanism behind them. In the present study, we exposed washed human platelets to 10 or 30 Gy X-rays at 0.25 Gy/min. Flow cytometry, aggregometry, and western blot were performed to investigate the effect of X-rays on platelet degranulation, integrin activation, platelet aggregation, and apoptosis. It was found that X-rays immediately induced granular secretions with no effect on GP IIb/IIIa activation. Not surprisingly, due to granule secretions in irradiated platelets, platelet aggregation was significantly reduced. In contrast to granular secretions and platelet aggregation, X-rays induced mitochondrial transmembrane potential depolarization in a time-dependent manner to induce apoptosis and activated protein kinase C (PKC) signaling. This study revealed and explained the molecular mechanism activated by X-rays in washed human platelets. Here we also introduced Gö 6983, a PKC inhibitor, as an agent that counteracts X-ray-induced changes and maintains the integrity of platelets.

Involvement of redox signalling in tumour cell dormancy and metastasis

Decades of research on oncogene-driven carcinogenesis and gene-expression regulatory networks only started to unveil the complexity of tumour cellular and molecular biology. This knowledge has been successfully implemented in the clinical practice to treat primary tumours. In contrast, much less progress has been made in the development of new therapies against metastasis, which are the main cause of cancer-related deaths. More recently, the role of epigenetic and microenviromental factors has been shown to play a key role in tumour progression. Free radicals are known to communicate the intracellular and extracellular compartments, acting as second messengers and exerting a decisive modulatory effect on tumour cell signalling. Depending on the cellular and molecular context, as well as the intracellular concentration of free radicals and the activation status of the antioxidant system of the cell, the signalling equilibrium can be tilted either towards tumour cell survival and progression or cell death. In this regard, recent advances in tumour cell biology and metastasis indicate that redox signalling is at the base of many cell-intrinsic and microenvironmental mechanisms that control disseminated tumour cell fate and metastasis. In this manuscript, we will review the current knowledge about redox signalling along the different phases of the metastatic cascade, including tumour cell dormancy, making emphasis on metabolism and the establishment of supportive microenvironmental connections, from a redox perspective.

The Role of Reprogrammed Glucose Metabolism in Cancer

Cancer cells reprogram their metabolism to meet biosynthetic needs and to adapt to various microenvironments. Accelerated glycolysis offers proliferative benefits for malignant cells by generating glycolytic products that move into branched pathways to synthesize proteins, fatty acids, nucleotides, and lipids. Notably, reprogrammed glucose metabolism and its associated events support the hallmark features of cancer such as sustained cell proliferation, hijacked apoptosis, invasion, metastasis, and angiogenesis. Overproduced enzymes involved in the committed steps of glycolysis (hexokinase, phosphofructokinase-1, and pyruvate kinase) are promising pharmacological targets for cancer therapeutics. In this review, we summarize the role of reprogrammed glucose metabolism in cancer cells and how it can be manipulated for anti-cancer strategies.

The metabolomics of a protein kinase C delta (PKCδ) knock-out mouse model

INTRODUCTION

PKCδ is ubiquitously expressed in mammalian cells and its dysregulation plays a key role in the onset of several incurable diseases and metabolic disorders. However, much remains unknown about the metabolic pathways and disturbances induced by PKC deficiency, as well as the metabolic mechanisms involved.

OBJECTIVES

This study aims to use metabolomics to further characterize the function of PKC from a metabolomics standpoint, by comparing the full serum metabolic profiles of PKC deficient mice to those of wild-type mice.

METHODS

The serum metabolomes of PKCδ knock-out mice were compared to that of a wild-type strain using a GCxGC-TOFMS metabolomics research approach and various univariate and multivariate statistical analyses.

RESULTS

Thirty-seven serum metabolite markers best describing the difference between PKCδ knock-out and wild-type mice were identified based on a PCA power value > 0.9, a t-test p-value < 0.05, or an effect size > 1. XERp prediction was also done to accurately select the metabolite markers within the 2 sample groups. Of the metabolite markers identified, 78.4% (29/37) were elevated and 48.65% of these markers were fatty acids (18/37). It is clear that a total loss of PKCδ functionality results in an inhibition of glycolysis, the TCA cycle, and steroid synthesis, accompanied by upregulation of the pentose phosphate pathway, fatty acids oxidation, cholesterol transport/storage, single carbon and sulphur-containing amino acid synthesis, branched-chain amino acids (BCAA), ketogenesis, and an increased cell signalling via N-acetylglucosamine.

CONCLUSION

The charaterization of the dysregulated serum metabolites in this study, may represent an additional tool for the early detection and screening of PKCδ-deficiencies or abnormalities.

Crucial Role of Reactive Oxygen Species (ROS) for the Proapoptotic Effects of Indirubin Derivatives in Cutaneous SCC Cells

Efficient drugs are needed for countering the worldwide high incidence of cutaneous squamous cell carcinoma (cSCC) and actinic keratosis. Indirubin derivatives represent promising candidates, but their effects in cSCC cells have not been reported before. Here, we investigated the efficacy of three indirubin derivatives (DKP-071, -073 and -184) in four cSCC cell lines. High efficacy was seen in SCL-I, SCL-II, SCC-12 and SCC-13, resulting in up to 80% loss of cell proliferation, 60% loss of cell viability and 30% induced apoptosis (10 µM). Apoptosis was further enhanced in combinations with TNF-related apoptosis-inducing ligand (TRAIL). Induction of reactive oxygen species (ROS) appeared as critical for these effects. Thus, antioxidative pretreatment completely abolished apoptosis as well as restored cell proliferation and viability. Concerning the pathways, complete activation of caspases cascades (caspases-3, -4, -6, -7, -8 and -9), loss of mitochondrial membrane potential, activation of proapoptotic PKCδ (protein kinase C delta), inhibition of STAT3 (signal transducer and activator of transcription 3), downregulation of antiapoptotic XIAP (X-linked inhibitor of apoptosis protein) and survivin as well as upregulation of the proapoptotic Bcl-2 protein Puma and the cell cycle inhibitor p21 were obtained. Importantly, all activation steps were prevented by antioxidants, thus proving ROS as a master regulator of indirubins' antitumor effects. ROS induction presently develops as an important issue in anticancer therapy.

Targeting Cutaneous T-Cell Lymphoma Cells by Ingenol Mebutate (PEP005) Correlates with PKCδ Activation, ROS Induction as Well as Downregulation of XIAP and c-FLIP

New therapeutic strategies are needed for cutaneous T-cell lymphoma (CTCL), and the plant extract ingenol mebutate (PEP005) may be considered. PEP005 has been approved for actinic keratosis, and proapoptotic activities were described in different cancer cells. Here, we aimed to investigate its efficacy in four CTCL cell lines and its mode of action. While HuT-78 and HH responded with induced apoptosis as well as with loss of cell viability and cell proliferation, MyLa and SeAx remained resistant. Interestingly, both sensitive and resistant cells showed caspase-8 activation and enhanced levels of reactive oxygen species (ROS), while final caspase-3 activation was restricted to sensitive cells. Apoptosis induction was prevented by the caspase inhibitor QVD-Oph as well as by the antioxidant vitamin E. Caspase activation by PEP005 may be explained to some extent by the downregulation of the caspase antagonistic proteins c-FLIP and XIAP in sensitive cells, whereas both proteins were strongly expressed in resistant cells. Finally, PEP005 resulted in the activation of proapoptotic PKCδ, and the PKC inhibitor bisindolylmaleimide I reduced apoptosis, caspase-3 processing and ROS production, as well as restored cell viability. In conclusion, PKCδ appeared as a central player in apoptosis regulation in CTCL cells, also suggesting its therapeutic targeting.

12-Deoxyphorbol Esters Induce Growth Arrest and Apoptosis in Human Lung Cancer A549 Cells Via Activation of PKC-δ/PKD/ERK Signaling Pathway

Prostratin, a non-tumor promoting 12-deoxyphorbol ester, has been reported as a protein kinase C (PKC) activator and is shown to have anti-proliferative activity in certain cancer cell types. Here we show that GRC-2, a prostratin analogue isolated from Euphorbia grandicornis, is ten-fold more potent than prostratin for inhibiting the growth of human non-small cell lung cancer (NSCLC) A549 cells. Flow cytometry assay revealed that GRC-2 and prostratin inhibited cell cycle progression at the G2/M phase and induced apoptosis. The cytotoxic effect of GRC-2 and prostratin was accompanied by activation and nuclear translocation of PKC-δ and PKD as well as hyperactivation of extracellular signal-related kinase (ERK). Knockdown of either PKC-δ, PKD or ERK significantly protected A549 cancer cells from GRC-2- and prostratin-induced growth arrest as well as apoptosis. Taken together, our results have shown that prostratin and a more potent analogue GRC-2 reduce cell viability in NSCLC A549 cells, at least in part, through activation of the PKC-δ/PKD/ERK pathway, suggesting the potential of prostratin and GRC-2 as anticancer agents.

Protein Kinase C δ (PKCδ) Attenuates Bleomycin Induced Pulmonary Fibrosis via Inhibiting NF-κB Signaling Pathway

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive and lethal interstitial lung disease characterized by consistent pulmonary inflammation. Although protein kinase C delta (PKCδ) is involved in broad scope cellular response, the role of PKCδ in IPF is complicated and has not been fully defined yet. Here, we reported that PKCδ deficiency (PKCδ^-/-) aggravated bleomycin (BLM)-induced pulmonary fibrosis and inflammation. Upon challenge with BLM, the pulmonary capillary permeability, immune cell infiltration, inflammatory cytokine production, and collagen deposition were enhanced in PKCδ^-/- mice compared to that in PKCδ^+/+ mice. In response to poly(I:C) stimulation, PKCδ deficient macrophages displayed an increased production of IL-1β, IL-6, TNF-α, and IL-33, which were associated with an enhanced NF-κB activation. Furthermore, we found that PKCδ could directly bind to and phosphorylate A20, an inhibitory protein of NF-κB signal. These results suggested that PKCδ may inhibit the NF-κB signaling pathway via enhancing the stability and activity of A20, which in turn attenuates pulmonary fibrosis, suggesting that PKCδ is a promising target for treating pulmonary fibrosis.

Diallyl Trisulfide (DATS) Suppresses AGE-Induced Cardiomyocyte Apoptosis by Targeting ROS-Mediated PKCδ Activation

Chronic high-glucose exposure results in the production of advanced glycation end-products (AGEs) leading to reactive oxygen species (ROS) generation, which contributes to the development of diabetic cardiomyopathy. PKCδ activation leading to ROS production and mitochondrial dysfunction involved in AGE-induced cardiomyocyte apoptosis was reported in our previous study. Diallyl trisulfide (DATS) is a natural cytoprotective compound under various stress conditions. In this study, the cardioprotective effect of DATS against rat streptozotocin (STZ)-induced diabetic mellitus (DM) and AGE-induced H9c2 cardiomyoblast cell/neonatal rat ventricular myocyte (NRVM) damage was assessed. We observed that DATS treatment led to a dose-dependent increase in cell viability and decreased levels of ROS, inhibition of PKCδ activation, and recuded apoptosis-related proteins. Most importantly, DATS reduced PKCδ mitochondrial translocation induced by AGE. However, apoptosis was not inhibited by DATS in cells transfected with PKCδ-wild type (WT). Inhibition of PKCδ by PKCδ-kinase-deficient (KD) or rottlerin not only inhibited cardiac PKCδ activation but also attenuated cardiac cell apoptosis. Interestingly, overexpression of PKCδ-WT plasmids reversed the inhibitory effects of DATS on PKCδ activation and apoptosis in cardiac cells exposed to AGE, indicating that DATS may inhibit AGE-induced apoptosis by downregulating PKCδ activation. Similar results were observed in AGE-induced NRVM cells and STZ-treated DM rats following DATS administration. Taken together, our results suggested that DATS reduced AGE-induced cardiomyocyte apoptosis by eliminating ROS and downstream PKCδ signaling, suggesting that DATS has potential in diabetic cardiomyopathy (DCM) treatment.

Expression of genes involved in apoptosis is dysregulated in mucopolysaccharidoses as revealed by pilot transcriptomic analyses

Mucopolysaccharidoses (MPS), a group of lysosomal storage diseases (LSD), are inherited disorders caused by mutations in genes coding for enzymes involved in the degradation of glycosaminoglycans (GAGs). Therefore, accumulated GAGs in lysosomes lead to severe symptoms in patients and significantly shortened life span. Although GAG accumulation in cells is the primary cellular defect in MPS, recent reports indicated that severe changes in cellular processes occur there as secondary or tertiary effects, which may contribute significantly to the disease pathomechanism. Apoptosis is one of such process, while mechanisms leading to dysregulation of this process in MPS remain largely unknown. To learn about these mechanisms, we have performed transcriptomic studies using cultures of fibroblasts derived from patients suffering from all types and subtypes of MPS, and assessed genes related to apoptosis. We found that there are significant changes in expression levels of many such genes relative to control fibroblasts (Human Dermal Fibroblasts-adult cell line), and the number of down- or up-regulated transcripts was between 19 and 73 in different MPS types. We have identified apoptosis-related genes, which were considerably dysregulated in many MPS types, as well as those in which expression was significantly changed in specific MPS types. BNIP3, C1D, CLU, GPER1, KREMEN1, and PRKCD genes displayed the most changed expression profiles in most MPS types relative to control cells. Caspase 3/7 activity was increased in MPS IVA and IX. These results indicate that changes in apoptosis, observed in MPS, may arise, at least partially, from dysregulation of genes coding for proteins involved in this process.

Reactive Oxygen Species-Induced Lipid Peroxidation in Apoptosis, Autophagy, and Ferroptosis

Reactive oxygen species- (ROS-) induced lipid peroxidation plays a critical role in cell death including apoptosis, autophagy, and ferroptosis. This fundamental and conserved mechanism is based on an excess of ROS which attacks biomembranes, propagates lipid peroxidation chain reactions, and subsequently induces different types of cell death. A highly evolved sophisticated antioxidant system exists that acts to protect the cells from oxidative damage. In this review, we discussed how ROS propagate lipid peroxidation chain reactions and how the products of lipid peroxidation initiate apoptosis and autophagy in current models. We also discussed the mechanism of lipid peroxidation during ferroptosis, and we summarized lipid peroxidation in pathological conditions of critical illness. We aim to bring a more global and integrative sight to know how different ROS-induced lipid peroxidation occurs among apoptosis, autophagy, and ferroptosis.

Determination of the Role and Active Sites of PKC-Delta-Like from Lamprey in Innate Immunity

Protein kinase C-δ (PKC-δ) is an important protein in the immune system of higher vertebrates. Lampreys, as the most primitive vertebrates, have a uniquevariable lymphocyte receptor (VLR) immune system. PKC-δ-like is a crucial functional gene in lampreys and is highly expressed in their immune organs. In this study, lampreys were stimulated with different immunogens, and lipopolysaccharide (LPS) was found to increase the expression of PKC-δ-like. Overexpression of PKC-δ-like could also effectively activate the innate immune response. We further demonstrated that PKC-δ-like-CF, a catalytic fragment of PKC-δ-like, is responsible for activating the innate immune response, and Thr-211, which is Thr-419 of PKC-δ-like, was confirmed to be the key site affecting PKC-δ-like-CF activity. These results indicated that PKC-δ-like from lamprey may have an important role in the innate immune response.

Genome Scan for Genomic Regions and Genes Associated with Growth Trait in Pacific White Shrimp Litopeneaus vannamei

The Pacific white shrimp Litopeneaus vannmei (L. vannmei) is a predominant aquaculture shrimp species worldwide, and it is considered as the aquaculture species with the highest single output value. Advances in selective breeding have accelerated the development of L. vannmei aquaculture. Recently, the genome-wide association studies (GWAS) have been applied in aquaculture animals and markers associated with economic traits were identified. In this study, we focused on the growth trait of L. vannamei and performed GWAS to identify SNPs or genes associated with growth. Genomic regions in linkage group 7, 27, 33, and 38 were identified to be associated with body weight and body length of the shrimp. Further, candidate gene association analysis was performed in two independent populations and the result demonstrated that the SNPs in the genes protein kinase C delta type and ras-related protein Rap-2a were significantly associated with the growth trait of L. vannamei. This study showed that GWAS analysis is an efficient approach for screening trait-related markers or genes. The genomic regions and genes identified in this study are essential for further fine mapping of growth-related genes. The identified markers will provide useful information for marker-assisted selection in L. vannamei.

The Role of Tyrosine Phosphorylation of Protein Kinase C Delta in Infection and Inflammation

Protein Kinase C (PKC) is a family composed of phospholipid-dependent serine/threonine kinases that are master regulators of inflammatory signaling. The activity of different PKCs is context-sensitive and these kinases can be positive or negative regulators of signaling pathways. The delta isoform (PKCδ) is a critical regulator of the inflammatory response in cancer, diabetes, ischemic heart disease, and neurodegenerative diseases. Recent studies implicate PKCδ as an important regulator of the inflammatory response in sepsis. PKCδ, unlike other members of the PKC family, is unique in its regulation by tyrosine phosphorylation, activation mechanisms, and multiple subcellular targets. Inhibition of PKCδ may offer a unique therapeutic approach in sepsis by targeting neutrophil-endothelial cell interactions. In this review, we will describe the overall structure and function of PKCs, with a focus on the specific phosphorylation sites of PKCδ that determine its critical role in cell signaling in inflammatory diseases such as sepsis. Current genetic and pharmacological tools, as well as in vivo models, that are used to examine the role of PKCδ in inflammation and sepsis are presented and the current state of emerging tools such as microfluidic assays in these studies is described.

The Caspase-3/PKCδ/Akt/VEGF-A Signaling Pathway Mediates Tumor Repopulation during Radiotherapy

PURPOSE

Tumor repopulation is known as a major cause of treatment failure and/or tumor recurrence after radiotherapy. The underlying mechanism remains unclear. Our previous study demonstrated that irradiated apoptotic cells mediated tumor repopulation, in which caspase-3 played an important role. Herein, we investigated downstream effectors of caspase-3 involved in this process.

EXPERIMENTAL DESIGN

A dominant-negative protein kinase Cδ (DN_PKCδ) mutant that could not be cleaved by caspase-3 and therefore could not be activated by irradiation-induced apoptosis was constructed. DN_PKCδ stably transduced tumor cells were compared with wild-type tumor cells for their growth stimulation effects in in vitro and in vivo tumor repopulation models. Downstream effectors of caspase-3 and PKCδ were investigated. The role of PKCδ was further verified in human colorectal tumor specimens.

RESULTS

Inactivation of caspase-3 or caspase-7 attenuated tumor repopulation and weakened PKCδ cleavage. Both DN_PKCδ and PKCδ inhibitors restrained tumor repopulation both in vitro and in vivo. Phosphorylated Akt was attenuated in caspase-3-, caspase-7-, or PKCδ-inactivated tumor cells. Furthermore, expression of vascular endothelial growth factor (VEGF)-A but not hypoxia-inducible factor 1α (HIF1α) was decreased in PKCδ- or Akt-inactivated tumor cells. In addition, inhibition of p-Akt, HIF1α, VEGF-A, or VEGF-A receptor reduced tumor repopulation significantly. Finally, increased nuclear translocation of PKCδ in colorectal tumor specimens was associated with worse patient prognosis.

CONCLUSIONS

The caspase-3/PKCδ/Akt/VEGF-A axis is involved in tumor repopulation and could be exploited as a potential target to enhance the efficacy of radiotherapy.

Aflatoxin production and in vitro toxicity of Aspergilli section Flavi isolated from air samples collected from different environments

Aspergilli section Flavi, originally isolated from air samples collected from inhabited apartments (AP), unoccupied basements (BS), and processing facilities of a grain mill (GM), were analyzed for their potential to produce aflatoxin B₁ (AFB₁) on solid media. The isolates were further characterized with regard to their cytotoxic, genotoxic, and pro-inflammatory properties in vitro. Aspergilli were identified based on partial calmodulin (CaM) gene sequencing; the producing capacities of isolates were analyzed by HPLC/FLD and confirmed by genes in biosynthesis (aflR, norA, omtA). In the grain mill, the Aspergilli section Flavi (up to 1.3 × 10⁶ cfu/m³) dominated by AFB₁-producing Aspergillus flavus (71%, 4.5-5254 ng/ml) which showed a serious health risk for workers. Living environments were not relevant sources of exposure. After 24 h, AFB₁ (1-100 μmol/l) reduced cell viability (MTT test) in both A549 cells and THP-1 macrophage-like cells without reaching IC₅₀. In A549 cells, the extract of the AFB₁-producing A. flavus significantly decreased cell viability but not below 50%. THP-1 macrophage-like cells were more sensitive to both extracts, but IC₅₀ was obtained only for the AFB₁-producing strain (0.37 mg/ml; AFB₁ 2.78 μmol/l). AFB₁ (1 and 10 μmol/l) induced significant DNA damage (tail intensity, alkaline comet assay) in A549 cells in contrast to Aspergilli extracts. AFB₁ elevated IL-6 and IL-8, while Aspergilli extracts increased IL-1β, TNF-α, and IL-17 release in THP-1 macrophages (ELISA). Chronic exposure to AFB₁ and/or other metabolites in airborne A. flavus from occupational environments may stimulate epithelial damage of airways accompanied by lowered macrophage viability.

PLOD3 suppression exerts an anti-tumor effect on human lung cancer cells by modulating the PKC-delta signaling pathway

Current lung cancer treatments are far from satisfactory; thus, finding novel treatment targets is crucial. We recently identified procollagen-lysine, 2-oxoglutarate 5-dioxygenase 3 (PLOD3), which is involved in fibrosis and tissue remodeling as a radioresistance-related protein in lung cancer cells; however, its mechanism is unclear. In this study, we designed human PLOD3-specific short interfering (si)RNAs and tested their effects on tumor growth inhibition in vitro and in vivo. PLOD3 knockdown overcame chemoresistance and decreased radioresistance by inducing caspase-3-dependent apoptosis in lung cancer cells. Furthermore, PLOD3 interacted with PKCδ to activate caspase-2,4-dependent apoptosis through ER-stress-induced IRE1α activation and the downstream unfolded-protein response pathway. In a mouse xenograft model, PLOD3 knockdown promoted radiation-induced tumor growth inhibition, without side effects. Moreover, lung cancer patients with high PLOD3 expression showed poorer prognosis than those with low PLOD3 expression upon radiotherapy, suggesting that PLOD3 promotes tumor growth. Therefore, PLOD3 siRNA suppresses radioresistance and chemoresistance by inducing apoptosis and renders PLOD3 as a candidate lung cancer biomarker. PLOD3 gene therapy might enhance the efficacy of radiotherapy or chemotherapy in lung cancer patients.

Role of protein kinase Cδ in dopaminergic neurotoxic events

The pro-apoptotic role of Protein kinase Cδ (PKCδ), a member of the novel PKC subfamily, has been well-documented in various pathological conditions. In the central nervous system, the possible role of PKCδ has been studied, mainly in the condition of dopaminergic loss. It has been suggested that the phosphorylation of PKCδ at tyrosine 311 residue (Tyr³¹¹) by redox-sensitive Src family kinases (SFKs) is critical for the caspase-3-mediated proteolytic cleavage, which produces the constitutively active cleaved form of PKCδ. Mitochondrial translocation of cleaved PKCδ has been suggested to facilitate mitochondria-derived apoptosis and oxidative burdens. Moreover, it has been suggested that PKCδ contribute to neuroinflammation through the transformation of microglia into the pro-inflammatory M1 phenotype and the assembly of membrane NADPH oxidase in dopaminergic impairments. Interestingly, mitochondrial respiratory chain inhibitors or neuroinflammogens have shown to induce PKCδ activation in dopaminergic systems. Thus, PKCδ activation may be one of the pivotal causes of neuropathologic events, and could amplify these processes further in a positive feedback manner. Furthermore, PKCδ may play an intermediary role in connecting each neuropathologic event. This review affords insight into the role of PKCδ in various dopaminergic neurotoxic models, which could provide a potential target for mitigating dopaminergic neurotoxicity.

The roles of PKCs in regulating autophagy

PURPOSE

Autophagy, as a highly conserved cellular degradation and recycling process, plays an important part in maintaining cellular homeostasis. PKC signaling is involved in multiple pathways including cell cycle progression, tumorigenesis, migration and autophagy.

METHODS

Literatures about PKC and autophagy from PubMed databases were reviewed in this study.

RESULTS

Studies regarding the association of PKC and autophagy remain debatable. Different duration of the stimulation of autophagy and distinct cell contexts result in different function of PKC in regulating autophagy. The subcellular localization of PKCs and their downstream regulators may influence the autophagy regulation as well. As important intracellular components, the mitochondria play an important role in regulating autophagy, by metabolic modulation and structural derangement.

CONCLUSION

Phase II studies regarding PKC-β inhibitor, enzastaurin, showed promising results in MCL, DLBCL and recurrent high-grade gliomas. However, the detailed mechanism is still in need. The mechanism of PKC-β in mediating autophagy in lymphoma and high-grade gliomas remains elusive as well. Moreover, several studies were in agreement that rottlerin enhanced autophagy in breast cancer cells, which warrants further clinical studies to verify PKC-δ as a therapeutic target. Thus, identifying the function of PKC in modulating autophagy and conducting related clinical studies help find novel target for chemotherapy.

Pkcδ Activation is Involved in ROS-Mediated Mitochondrial Dysfunction and Apoptosis in Cardiomyocytes Exposed to Advanced Glycation End Products (Ages)

Diabetic patients exhibit serum AGE accumulation, which is associated with reactive oxygen species (ROS) production and diabetic cardiomyopathy. ROS-induced PKCδ activation is linked to mitochondrial dysfunction in human cells. However, the role of PKCδ in cardiac and mitochondrial dysfunction caused by AGE in diabetes is still unclear. AGE-BSA-treated cardiac cells showed dose- and time-dependent cell apoptosis, ROS generation, and selective PKCδ activation, which were reversed by NAC and rotenone. Similar tendency was also observed in diabetic and obese animal hearts. Furthermore, enhanced apoptosis and reduced survival signaling by AGE-BSA or PKCδ-WT transfection were reversed by kinase-deficient (KD) of PKCδ transfection or PKCδ inhibitor, respectively, indicating that AGE-BSA-induced cardiomyocyte death is PKCδ-dependent. Increased levels of mitochondrial mass as well as mitochondrial fission by AGE-BSA or PKCδ activator were reduced by rottlerin, siPKCδ or KD transfection, indicating that the AGE-BSA-induced mitochondrial damage is PKCδ-dependent. Using super-resolution microscopy, we confirmed that PKCδ colocalized with mitochondria. Interestingly, the mitochondrial functional analysis by Seahorse XF-24 flux analyzer showed similar results. Our findings indicated that cardiac PKCδ activation mediates AGE-BSA-induced cardiomyocyte apoptosis via ROS production and may play a key role in the development of cardiac mitochondrial dysfunction in rats with diabetes and obesity.

Evolving mechanisms of vascular smooth muscle contraction highlight key targets in vascular disease

Vascular smooth muscle (VSM) plays an important role in the regulation of vascular function. Identifying the mechanisms of VSM contraction has been a major research goal in order to determine the causes of vascular dysfunction and exaggerated vasoconstriction in vascular disease. Major discoveries over several decades have helped to better understand the mechanisms of VSM contraction. Ca2+ has been established as a major regulator of VSM contraction, and its sources, cytosolic levels, homeostatic mechanisms and subcellular distribution have been defined. Biochemical studies have also suggested that stimulation of Gq protein-coupled membrane receptors activates phospholipase C and promotes the hydrolysis of membrane phospholipids into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). IP3 stimulates initial Ca2+ release from the sarcoplasmic reticulum, and is buttressed by Ca2+ influx through voltage-dependent, receptor-operated, transient receptor potential and store-operated channels. In order to prevent large increases in cytosolic Ca2+ concentration ([Ca2+]c), Ca2+ removal mechanisms promote Ca2+ extrusion via the plasmalemmal Ca2+ pump and Na+/Ca2+ exchanger, and Ca2+ uptake by the sarcoplasmic reticulum and mitochondria, and the coordinated activities of these Ca2+ handling mechanisms help to create subplasmalemmal Ca2+ domains. Threshold increases in [Ca2+]c form a Ca2+-calmodulin complex, which activates myosin light chain (MLC) kinase, and causes MLC phosphorylation, actin-myosin interaction, and VSM contraction. Dissociations in the relationships between [Ca2+]c, MLC phosphorylation, and force have suggested additional Ca2+ sensitization mechanisms. DAG activates protein kinase C (PKC) isoforms, which directly or indirectly via mitogen-activated protein kinase phosphorylate the actin-binding proteins calponin and caldesmon and thereby enhance the myofilaments force sensitivity to Ca2+. PKC-mediated phosphorylation of PKC-potentiated phosphatase inhibitor protein-17 (CPI-17), and RhoA-mediated activation of Rho-kinase (ROCK) inhibit MLC phosphatase and in turn increase MLC phosphorylation and VSM contraction. Abnormalities in the Ca2+ handling mechanisms and PKC and ROCK activity have been associated with vascular dysfunction in multiple vascular disorders. Modulators of [Ca2+]c, PKC and ROCK activity could be useful in mitigating the increased vasoconstriction associated with vascular disease.

Mechanistic study of nonivamide enhancement of hyperthermia-induced apoptosis in U937 cells

Hyperthermia is one therapeutic tool for damaging and killing cancer cells, with minimal injury to normal tissues. However, its cytotoxic effects alone are insufficient for quantitative cancer cell death. To overcome this limitation, several studies have explored non-toxic enhancers for hyperthermia-induced cell death. Capsaicin may be applicable as a therapeutic tool against various types of cancer. In the present study, we employed nonivamide, a less-pungent capsaicin analogue, to investigate its possible enhancing effects on hyperthermia-induced apoptosis; moreover, we analyzed its molecular mechanism. Treatment of U937 cells at 44 °C for 15 min, combined with nonivamide 50 μM, revealed enhancement of apoptosis. Significant increases in reactive oxygen species generation, mitochondrial dysfunction, and cleaved caspase-3 were observed during the combined treatment; these were accompanied by an increase in pro-apoptotic Bcl-2 family proteins and a decrease in anti-apoptotic Bcl-2 proteins. In addition, significant increases in p-JNK and p-p38 were detected, following the combined treatment. In conclusion, nonivamide enhanced hyperthermia-induced apoptosis via a mitochondrial-caspase dependent pathway. The underlying mechanism may include elevation of intracellular reactive oxygen species, mitochondrial dysfunction, and increased activation of JNK and p38.

Discovery of a small-molecule protein kinase Cδ-selective activator with promising application in colon cancer therapy

Protein kinase C (PKC) isozymes play major roles in human diseases, including cancer. Yet, the poor understanding of isozymes-specific functions and the limited availability of selective pharmacological modulators of PKC isozymes have limited the clinical translation of PKC-targeting agents. Here, we report the first small-molecule PKCδ-selective activator, the 7α-acetoxy-6β-benzoyloxy-12-O-benzoylroyleanone (Roy-Bz), which binds to the PKCδ-C1-domain. Roy-Bz potently inhibited the proliferation of colon cancer cells by inducing a PKCδ-dependent mitochondrial apoptotic pathway involving caspase-3 activation. In HCT116 colon cancer cells, Roy-Bz specifically triggered the translocation of PKCδ but not other phorbol ester responsive PKCs. Roy-Bz caused a marked inhibition in migration of HCT116 cells in a PKCδ-dependent manner. Additionally, the impairment of colonosphere growth and formation, associated with depletion of stemness markers, indicate that Roy-Bz also targets drug-resistant cancer stem cells, preventing tumor dissemination and recurrence. Notably, in xenograft mouse models, Roy-Bz showed a PKCδ-dependent antitumor effect, through anti-proliferative, pro-apoptotic, and anti-angiogenic activities. Besides, Roy-Bz was non-genotoxic, and in vivo it had no apparent toxic side effects. Collectively, our findings reveal a novel promising anticancer drug candidate. Most importantly, Roy-Bz opens the way to a new era on PKC biology and pharmacology, contributing to the potential redefinition of the structural requirements of isozyme-selective agents, and to the re-establishment of PKC isozymes as feasible therapeutic targets in human diseases.

Dual action of NSC606985 on cell growth and apoptosis mediated through PKCδ in prostatic cancer cells

Chemotherapy is a vital therapeutic strategy for castration-resistant prostate cancer (CRPC). We have previously shown that NSC606985 (NSC), a camptothecin (CPT) analog, induced cell apoptosis via interacting with topoisomerase I (Topo I) in prostate cancer cells. In the present study, the effect and mechanism of CPT analogs in LAPC4 cells were investigated. LAPC-4 cells were treated with NSC, CPT, and topotecan. Cell proliferation, apoptosis, and protein kinase Cδ (PKCδ) subcellular activation were measured at different doses and time-points, with or without PKCδ inhibition or knockdown of PKCδ expression. NSC at doses ranging from 10 to 100 nM induced a dose-dependent increase in viable cell number and DNA biosynthesis with mild cell apoptosis, whereas, at doses ranging from 500 nM to 5 mM, NSC produced a dose-dependent decrease in cell proliferation and DNA biosynthesis with a significant induction of cell apoptosis. Both NSC-induced cell proliferation and apoptosis were blocked by knockdown of PKCδ with a specific RNAi, or by the co-administration of rottlerin, a PKCδ inhibitor. Moreover, NSC produced a dose-dependent subcellular activation of PKCδ. The dose-dependent dual action of NSC is mediated at least in part through the differential subcellular activation of PKCδ in LAPC4 cells. The demonstration of a differential cell response to camptothecin analogs would facilitate the identification of biomarker(s) to CPT sensitivity and promote the personalization of CPT chemotherapy in CRPC.

Protein kinase C delta phosphorylates ecdysone receptor B1 to promote gene expression and apoptosis under 20-hydroxyecdysone regulation

The nuclear receptor EcRB1, which is activated by the insect steroid hormone 20-hydroxyecdysone (20E), is reportedly phosphorylated by a protein kinase after 20E induction. However, the protein kinase has not been identified, and the significance of EcRB1 phosphorylation is unclear. In this study, we identified a protein kinase C δ (PKCδ) isoform (the E isoform) that phosphorylates EcRB1 in the lepidopteran Helicoverpa armigera, a serious agricultural pest worldwide, to promote apoptotic gene expression and apoptosis during metamorphosis. Through activation of the EcRB1/USP1 transcription complex by 20E, PKCδ expression was up-regulated in several tissues during the metamorphic stage. Knockdown of PKCδ caused failure to transition from larvae to pupae, prevented tissues from undergoing programmed cell death (PCD), and down-regulated the expression of the transcription factor Brz-7 and the apoptosis executors caspase-3 and caspase-6 The threonine residue at position 1343 of PKCδ was phosphorylated and was critical for its proapoptotic function. Overexpression of the PKCδ catalytic domain was localized to the nuclei in HaEpi cells, which increased caspase-3 activity and apoptosis. PKCδ directly phosphorylated a threonine residue at position 468 in the amino acid sequence of EcRB1. The phosphorylation of EcRB1 was critical for its heterodimeric interaction with the USP1 protein and for binding to the ecdysone response element. The data suggested that 20E up-regulates PKCδ expression to regulate EcRB1 phosphorylation for EcRB1/USP1 transcription complex formation, apoptotic gene transcription, and apoptosis.

Acyl-CoA thioesterase 7 is involved in cell cycle progression via regulation of PKCζ-p53-p21 signaling pathway

Acyl-CoA thioesterase 7 (ACOT7) is a major isoform of the ACOT family that catalyzes hydrolysis of fatty acyl-CoAs to free fatty acids and CoA-SH. However, canonical and non-canonical functions of ACOT7 remain to be discovered. In this study, for the first time, ACOT7 was shown to be responsive to genotoxic stresses such as ionizing radiation (IR) and the anti-cancer drug doxorubicin in time- and dose-dependent manners. ACOT7 knockdown induced cytostasis via activation of the p53-p21 signaling pathway without a DNA damage response. PKCζ was specifically involved in ACOT7 depletion-mediated cell cycle arrest as an upstream molecule of the p53-p21 signaling pathway in MCF7 human breast carcinoma and A549 human lung carcinoma cells. Of the other members of the ACOT family, including ACOT1, 4, 8, 9, 11, 12, and 13 that were expressed in human, ACOT4, 8, and 12 were responsive to genotoxic stresses. However, none of those had a role in cytostasis via activation of the PKCζ-p53-p21 signaling pathway. Analysis of the ACOT7 prognostic value revealed that low ACOT7 levels prolonged overall survival periods in breast and lung cancer patients. Furthermore, ACOT7 mRNA levels were higher in lung cancer patient tissues compared to normal tissues. We also observed a synergistic effect of ACOT7 depletion in combination with either IR or doxorubicin on cell proliferation in breast and lung cancer cells. Together, our data suggest that a low level of ACOT7 may be involved, at least in part, in the prevention of human breast and lung cancer development via regulation of cell cycle progression.

Novel small molecule inhibiting CDCP1-PKCδ pathway reduces tumor metastasis and proliferation

CUB domain‐containing protein‐1 (CDCP1) is a trans‐membrane protein predominantly expressed in various cancer cells and involved in tumor progression. CDCP1 is phosphorylated at tyrosine residues in the intracellular domain by Src family kinases and recruits PKCδ to the plasma membrane through tyrosine phosphorylation‐dependent association with the C2 domain of PKCδ, which in turn induces a survival signal in an anchorage‐independent condition. In this study, we used our cell‐free screening system to identify a small compound, glycoconjugated palladium complex (Pd‐Oqn), which significantly inhibited the interaction between the C2 domain of PKCδ and phosphorylated CDCP1. Immunoprecipitation assays demonstrated that Pd‐Oqn hindered the intercellular interaction of phosphorylated CDCP1 with PKCδ and also suppressed the phosphorylation of PKCδ but not that of ERK or AKT. In addition, Pd‐Oqn inhibited the colony formation of gastric adenocarcinoma 44As3 cells in soft agar as well as their invasion. In mouse models, Pd‐Oqn markedly reduced the peritoneal dissemination of gastric adenocarcinoma cells and the tumor growth of pancreatic cancer orthotopic xenografts. These results suggest that the novel compound Pd‐Oqn reduces tumor metastasis and growth by inhibiting the association between CDCP1 and PKCδ, thus potentially representing a promising candidate among therapeutic reagents targeting protein–protein interaction.

Hyperosmotic environment blunts effectivity of ischemic preconditioning against ischemia-reperfusion injury and improves ischemic tolerance in non-preconditioned isolated rat hearts

Several studies have shown that diabetes mellitus modulates heart resistance to ischemia and abrogates effectivity of cardioprotective interventions, such as ischemic preconditioning (IP). The aim of this study was to evaluate whether the effect of hyperglycemic conditions on the severity of ischemia-reperfusion (I/R) injury in preconditioned and non-preconditioned hearts (controls, C) is related to changes in osmotic activity of glucose. Experiments were performed in isolated rat hearts perfused according to Langendorff exposed to 30-min coronary occlusion/120-min reperfusion. IP was induced by two cycles of 5-min coronary occlusion/5-min reperfusion, prior to the long-term I/R. Hyperosmotic (HO) state induced by an addition of mannitol (11 mmol/l) to a standard Krebs-Henseleit perfusion medium significantly decreased the size of infarction and also suppressed a release of heart fatty acid binding protein (h-FABP - biomarker of cell injury) from the non-IP hearts nearly to 50 %, in comparison with normoosmotic (NO) mannitol-free perfusion. However, IP in HO conditions significantly increased the size of infarction and tended to elevate the release of h-FABP to the effluent from the heart. The results indicate that HO environment plays a cardioprotective role in the ischemic myocardium. On the other hand, increased osmolarity, similar to that in the hyperglycemic conditions, may play a pivotal role in a failure of IP to induce cardioprotection in the diabetic myocardium.

Role of DNA methylation in bisphenol A exposed mouse spermatocyte

As a widespread environmental contaminant, bisphenol A (2,2-bis(4-hydroxyphenyl)propane, BPA) has been implicated in male reproductive function injury. Previous studies have investigated the mechanisms of DNA damage and oxidative stress caused by BPA; however, little is known regarding its impact on DNA methylation. In this paper, we assessed the adverse effects of BPA on mouse spermatocytes and investigated a potential role of DNA methylation. We demonstrated that BPA exposure inhibited cell proliferation, reduced the DNA replication capacity, and triggered apoptosis in GC-2 cells. In addition, the global DNA methylation levels increased, and the relative expression levels of DNA methyltransferases (DNMTs) varied following BPA exposure. Thousands of distinct methylated sites were screened using microarray analysis. The expressions of myosin-binding protein H (mybph) and protein kinase C δ (prkcd) were verified to be regulated by DNA methylation. These findings indicate that BPA had toxicity in spermatocytes, and DNA methylation may play a vital role in the regulation of BPA-triggered spermatocyte toxicity.

Cadmium-induced heme-oxygenase-1 expression plays dual roles in autophagy and apoptosis and is regulated by both PKC-δ and PKB/Akt activation in NRK52E kidney cells

Heme oxygenase-1 (HO-1) protects cells against cadmium (Cd)-induced oxidative stress. However, the mechanism underlying this protection is not well understood. In this study, we elucidated the role of HO-1 in Cd-induced cytotoxicity. Exposure of NRK52E cells to Cd induced protein kinase B (PKB)/Akt, protein kinase C (PKC)-δ, and glycogen synthase kinase (GSK) 3αb phosphorylation, and eukaryotic initiation factor (eIF) 2α dephosphorylation. Pharmacological inhibition of Akt resulted in HO-1 suppression and eIF2α activation, which partially suppressed CHOP and PARP-1 cleavage, but promoted autophagy and decreased cell viability. Pharmacological inactivation of PKC-δ markedly suppressed Cd-induced phospho-serine (p-Ser) GSK3αβ, and HO-1, and partially inhibited PARP-1 cleavage, but massively induced autophagy and decreased cell viability. Pharmacological upregulation of p-Ser GSK3αβ enhanced Cd-induced HO-1, CHOP, and PARP-1 cleavage, but decreased autophagy. Genetic deficiency of GSK3β suppressed HO-1 and PARP-1 cleavage and increased autophagy. Genetic suppression of HO-1 reduced Cd-induced PARP-1 cleavage, but increased LC3-II. Cd exposure led to accumulation of p-PKC-δ, p-Ser GSK3αβ, and HO-1 in the nucleus and particulate fractions, suggesting that they have dual functions in response to Cd. N-acetylcysteine treatment suppressed Cd-induced activation of PKC-δ and Akt. These results indicate that HO-1 induced by Cd exposure is regulated by PKC-δ, p-Ser GSK3αβ, and PKB/Akt, which restrain autophagic cell death, but mildly induce apoptosis in NRK52E cells. Together, the results suggest that HO-1 expression in response to Cd maintains cellular homeostasis during oxidative stress.

Fungal Aflatoxins Reduce Respiratory Mucosal Ciliary Function

Aflatoxins are mycotoxins secreted by Aspergillus flavus, which can colonize the respiratory tract and cause fungal rhinosinusitis or bronchopulmonary aspergillosis. A. flavus is the second leading cause of invasive aspergillosis worldwide. Because many respiratory pathogens secrete toxins to impair mucociliary immunity, we examined the effects of acute exposure to aflatoxins on airway cell physiology. Using air-liquid interface cultures of primary human sinonasal and bronchial cells, we imaged ciliary beat frequency (CBF), intracellular calcium, and nitric oxide (NO). Exposure to aflatoxins (0.1 to 10 μM; 5 to 10 minutes) reduced baseline (~6-12%) and agonist-stimulated CBF. Conditioned media (CM) from A. fumigatus, A. niger, and A. flavus cultures also reduced CBF by ~10% after 60 min exposure, but effects were blocked by an anti-aflatoxin antibody only with A. flavus CM. CBF reduction required protein kinase C but was not associated with changes in calcium or NO. However, AFB2 reduced NO production by ~50% during stimulation of the ciliary-localized T2R38 receptor. Using a fluorescent reporter construct expressed in A549 cells, we directly observed activation of PKC activity by AFB2. Aflatoxins secreted by respiratory A. flavus may impair motile and chemosensory functions of airway cilia, contributing to pathogenesis of fungal airway diseases.

Kinase Signaling in Apoptosis Induced by Saturated Fatty Acids in Pancreatic β-Cells

Pancreatic β-cell failure and death is considered to be one of the main factors responsible for type 2 diabetes. It is caused by, in addition to hyperglycemia, chronic exposure to increased concentrations of fatty acids, mainly saturated fatty acids. Molecular mechanisms of apoptosis induction by saturated fatty acids in β-cells are not completely clear. It has been proposed that kinase signaling could be involved, particularly, c-Jun N-terminal kinase (JNK), protein kinase C (PKC), p38 mitogen-activated protein kinase (p38 MAPK), extracellular signal-regulated kinase (ERK), and Akt kinases and their pathways. In this review, we discuss these kinases and their signaling pathways with respect to their possible role in apoptosis induction by saturated fatty acids in pancreatic β-cells.

Protein Kinase C as Regulator of Vascular Smooth Muscle Function and Potential Target in Vascular Disorders

Vascular smooth muscle (VSM) plays an important role in maintaining vascular tone. In addition to Ca2+-dependent myosin light chain (MLC) phosphorylation, protein kinase C (PKC) is a major regulator of VSM function. PKC is a family of conventional Ca2+-dependent α, β, and γ, novel Ca2+-independent δ, ɛ, θ, and η, and atypical ξ, and ι/λ isoforms. Inactive PKC is mainly cytosolic, and upon activation it undergoes phosphorylation, maturation, and translocation to the surface membrane, the nucleus, endoplasmic reticulum, and other cell organelles; a process facilitated by scaffold proteins such as RACKs. Activated PKC phosphorylates different substrates including ion channels, pumps, and nuclear proteins. PKC also phosphorylates CPI-17 leading to inhibition of MLC phosphatase, increased MLC phosphorylation, and enhanced VSM contraction. PKC could also initiate a cascade of protein kinases leading to phosphorylation of the actin-binding proteins calponin and caldesmon, increased actin-myosin interaction, and VSM contraction. Increased PKC activity has been associated with vascular disorders including ischemia-reperfusion injury, coronary artery disease, hypertension, and diabetic vasculopathy. PKC inhibitors could test the role of PKC in different systems and could reduce PKC hyperactivity in vascular disorders. First-generation PKC inhibitors such as staurosporine and chelerythrine are not very specific. Isoform-specific PKC inhibitors such as ruboxistaurin have been tested in clinical trials. Target delivery of PKC pseudosubstrate inhibitory peptides and PKC siRNA may be useful in localized vascular disease. Further studies of PKC and its role in VSM should help design isoform-specific PKC modulators that are experimentally potent and clinically safe to target PKC in vascular disease.

Keratin impact on PKCδ- and ASMase-mediated regulation of hepatocyte lipid raft size - implication for FasR-associated apoptosis

Keratins are epithelial cell intermediate filament (IF) proteins that are expressed as pairs in a cell-differentiation-regulated manner. Hepatocytes express the keratin 8 and 18 pair (denoted K8/K18) of IFs, and a loss of K8 or K18, as in K8-null mice, leads to degradation of the keratin partner. We have previously reported that a K8/K18 loss in hepatocytes leads to altered cell surface lipid raft distribution and more efficient Fas receptor (FasR, also known as TNFRSF6)-mediated apoptosis. We demonstrate here that the absence of K8 or transgenic expression of the K8 G62C mutant in mouse hepatocytes reduces lipid raft size. Mechanistically, we find that the lipid raft size is dependent on acid sphingomyelinase (ASMase, also known as SMPD1) enzyme activity, which is reduced in absence of K8/K18. Notably, the reduction of ASMase activity appears to be caused by a less efficient redistribution of surface membrane PKCδ toward lysosomes. Moreover, we delineate the lipid raft volume range that is required for an optimal FasR-mediated apoptosis. Hence, K8/K18-dependent PKCδ- and ASMase-mediated modulation of lipid raft size can explain the more prominent FasR-mediated signaling resulting from K8/K18 loss. The fine-tuning of ASMase-mediated regulation of lipid rafts might provide a therapeutic target for death-receptor-related liver diseases.

Distinctive roles of PKC delta isozyme in platelet function

Platelet activation is a complex balance of positive and negative signaling pathways. Several protein kinase C (PKC) isoforms are expressed in human platelets. They are a major regulator of platelet granule secretion, activation and aggregation activity. One of those isoforms is the PKCδ isozyme, it has a central yet complex role in platelets such as opposite signaling functions depending on the nature of the agonist, it concentration and pathway. In fact, it has been shown that PKCδ has an overall negative influence on platelet function in response to collagen, while, following PAR stimulation, PKCδ has a positive effect on platelet function. Understanding the crucial role of PKCδ in platelet functions is recently emerging in the literature, therefore, further investigations should shed light into its specific role in hemostasis. In this review, we focus on the different roles of PKCδ in platelet activation, aggregation and thrombus formation.

Crosstalk between tumor suppressors p53 and PKCδ: Execution of the intrinsic apoptotic pathways

p53 and PKCδ are tumor suppressors that execute apoptotic mechanisms in response to various cellular stresses. p53 is a transcription factor that is frequently mutated in human cancers; it regulates apoptosis in transcription-dependent and -independent ways in response to genotoxic stresses. PKCδ is a serine/threonine protein kinase and mutated in human cancers. Available evidence shows that PKCδ activates p53 by direct and/or indirect mechanisms. Moreover, PKCδ is also implicated in the transcriptional regulation of p53 in response to DNA damage. Recent findings demonstrated that p53, in turn, binds onto the PKCδ promoter and induces its expression upon DNA damage to facilitate apoptosis. Both p53 and PKCδ are associated with the apoptotic mechanisms in the mitochondria by regulating Bcl-2 family proteins to provide mitochondrial outer membrane permeabilization. This review discusses the crosstalk between p53 and PKCδ in the context of apoptotic cell death and cancer therapy.

Combining Normobaric Oxygen with Ethanol or Hypothermia Prevents Brain Damage from Thromboembolic Stroke via PKC-Akt-NOX Modulation

In a thromboembolic stroke model after reperfusion by recombinant tissue plasminogen activator (rt-PA), we aimed to determine whether therapeutic hypothermia (TH) and ethanol (EtOH) in combination with low concentration (60 %) of normobaric oxygen (NBO) enhanced neuroprotection, as compared to using each of these agents alone. We further aimed to elucidate a potential role of the NADPH oxidase (NOX), phosphorylated protein kinase B (Akt), and protein kinase C-δ (PKC-δ) pathway in oxidative stress and neuroprotection. In Sprague-Dawley rats, a focal middle cerebral artery (MCA) occlusion was induced by an autologous embolus in the following experimental groups: rt-PA treatment alone, rt-PA + NBO treatment, rt-PA + TH at 33 °C, rt-PA + EtOH, rt-PA + NBO + EtOH, rt-PA + NBO + TH, rt-PA + NOX inhibitor, rt-PA + EtOH + NOX inhibitor, or rt-PA + EtOH + Akt inhibitor. Control groups included sham-operated without stroke or stroke without treatment. Infarct volume and neurological deficit were assessed at 24 h after rt-PA-induced reperfusion with or without treatments. ROS levels, NOX activity, and the protein expression of NOX subunits p22^phox, p47^phox, p67^phox, gp91^phox, as well as PKC-δ and phosphorylated Akt were measured at 3 and 24 h after rt-PA-induced reperfusion. Following rt-PA in thromboembolic stroke rats, NBO combined with TH or EtOH more effectively decreased infarct volume and neurological deficit, as well as reactive oxygen species (ROS) production than with any of the used monotherapies. NOX activity and subunit expressions were downregulated and temporally associated with reduced PKC-δ and increased p-Akt expression. The present study demonstrated that combining NBO with either TH or EtOH conferred similar neuroprotection via modulation of NOX activation. The results suggest a role of Akt in NOX activation and implicate an upstream PKC-δ pathway in the Akt regulation of NOX. It is possible to substitute EtOH for TH, thus circumventing the difficulties in clinical application of TH through the comparatively easier usage of EtOH as a potential stroke management.

δV1-1 Reduces Pulmonary Ischemia Reperfusion-Induced Lung Injury by Inhibiting Necrosis and Mitochondrial Localization of PKCδ and p53

Ischemia-reperfusion (IR)-induced lung injury is one of the major contributing factors of morbidity and mortality after lung transplantation. To determine the IR-induced molecular changes in lung epithelial cells, we developed a cell-culture model that simulates lung preservation and transplantation. Six hours of cold ischemic time (CIT) and reperfusion elicited production of multiple inflammatory cytokines and chemokines and increased expression of endoplasmic reticulum (ER) proteins. Prolonged hypothermic condition (18 h CIT) reduced ER stress protein levels, and induced apoptosis and necrosis (via mechanisms related to mitochondrial permeability transition pore opening). Protein kinase C (PKCδ) was activated during CIT, and its downregulation via small interference (si) (in siRNA) RNA reduced IR-induced cytokine production and apoptotic cell death. δV1-1, a PKCδ peptide inhibitor, reduced translocation of PKCδ and p53 to the mitochondria after 18 h CIT, rescued ER stress protein expression, and converted the major mode of cell death from necrosis to apoptosis. Administration of δV1-1 effectively reduced lung transplantation and IR-induced pulmonary injury in rats. Therefore, inhibition of PKCδ by δV1-1 could be an effective strategy to ameliorate IR-induced lung injury by inhibiting the signaling pathways leading to necrosis.

C-H Oxidation of Ingenanes Enables Potent and Selective Protein Kinase C Isoform Activation

Ingenol derivatives with varying degrees of oxidation were prepared by two-phase terpene synthesis. This strategy has allowed access to analogues that cannot be prepared by semisynthesis from natural ingenol. Complex ingenanes resulting from divergent C-H oxidation of a common intermediate were found to interact with protein kinase C in a manner that correlates well with the oxidation state of the ingenane core. Even though previous work on ingenanes has suggested a strong correlation between potential to activate PKCδ and induction of neutrophil oxidative burst, the current study shows that the potential to activate PKCβII is of key importance while interaction with PKCδ is dispensable. Thus, key modifications of the ingenane core allowed PKC isoform selectivity wherein PKCδ-driven activation of keratinocytes is strongly reduced or even absent while PKCβII-driven activation of neutrophils is retained.