Protein kinase C-α (PKCα) modulates cell apoptosis by stimulating nuclear translocation of NF-kappa-B p65 in urothelial cell carcinoma of the bladder

Network and Experimental Pharmacology on Mechanism of Yixintai Regulates the TMAO/PKC/NF-κB Signaling Pathway in Treating Heart Failure

Objective

This study aims to explore the mechanism of action of Yixintai in treating chronic ischemic heart failure by combining bioinformatics and experimental validation.

Materials and Methods

Five potential drugs for treating heart failure were obtained from Yixintai (YXT) through early mass spectrometry detection. The targets of YXT for treating heart failure were obtained by a search of online databases. Gene ontology (GO) functional enrichment analysis and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analyses were conducted on the common targets using the DAVID database. A rat heart failure model was established by ligating the anterior descending branch of the left coronary artery. A small animal color Doppler ultrasound imaging system detected cardiac function indicators. Hematoxylin-eosin (HE), Masson's, and electron microscopy were used to observe the pathological morphology of the myocardium in rats with heart failure. The network pharmacology analysis results were validated by ELISA, qPCR, and Western blotting.

Results

A total of 107 effective targets were obtained by combining compound targets and eliminating duplicate values. PPI analysis showed that inflammation-related proteins (TNF and IL1B) were key targets for treating heart failure, and KEGG enrichment suggested that NF-κB signaling pathway was a key pathway for YXT treatment of heart failure. Animal model validation results indicated the following: YXT can significantly reduce the content of intestinal microbiota metabolites such as trimethylamine oxide (TMAO) and improve heart failure by improving the EF and FS values of heart ultrasound in rats and reducing the levels of serum NT-proBNP, ANP, and BNP to improve heart failure. Together, YXT can inhibit cardiac muscle hypertrophy and fibrosis in rats and improve myocardial ultrastructure and serum IL-1β, IL-6, and TNF-α levels. These effects are achieved by inhibiting the expressions of NF-κB and PKC.

Conclusion

YXT regulates the TMAO/PKC/NF-κB signaling pathway in heart failure.

Apoptosis and eryptosis: similarities and differences

Eryptosis is a regulated cell death (RCD) of mature erythrocytes initially described as a counterpart of apoptosis for enucleated cells. However, over the recent years, a growing number of studies have emphasized certain differences between both cell death modalities. In this review paper, we underline the hallmarks of eryptosis and apoptosis and highlight resemblances and dissimilarities between both RCDs. We summarize and critically discuss differences in the impact of caspase-3, Ca2+ signaling, ROS signaling pathways, opposing roles of casein kinase 1α, protein kinase C, Janus kinase 3, cyclin-dependent kinase 4, and AMP-activated protein kinase to highlight a certain degree of divergence between apoptosis and eryptosis. This review emphasizes the crucial importance of further studies that focus on deepening our knowledge of cell death machinery and identifying novel differences between cell death of nucleated and enucleated cells. This might provide evidence that erythrocytes can be defined as viable entities capable of programmed cell destruction. Additionally, the revealed cell type-specific patterns in cell death can facilitate the development of cell death-modulating therapeutic agents.

Erythronecroptosis: an overview of necroptosis or programmed necrosis in red blood cells

Necroptosis is considered a programmed necrosis that requires receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3), and pore-forming mixed lineage kinase domain-like protein (MLKL) to trigger a regulated cell membrane lysis. Membrane rupture in necroptosis has been shown to fuel innate immune response due to release of damage-associated molecular patterns (DAMPs). Recently published studies indicate that mature erythrocytes can undergo necroptosis as well. In this review, we provide an outline of multiple cell death modes occurring in erythrocytes, discuss possible immunological aspects of diverse erythrocyte cell deaths, summarize available evidence related to the ability of erythrocytes to undergo necroptosis, outline key involved molecular mechanisms, and discuss the potential implication of erythrocyte necroptosis in the physiology and pathophysiology. Furthermore, we aim to highlight the interplay between necroptosis and eryptosis signaling in erythrocytes, emphasizing specific characteristics of these pathways distinct from their counterparts in nucleated cells. Thus, our review provides a comprehensive summary of the current knowledge of necroptosis in erythrocytes. To reflect critical differences between necroptosis of nucleated cells and necroptosis of erythrocytes, we suggest a term erythronecroptosis for necroptosis of enucleated cells.

Potential implications of protein kinase Cα in pathophysiological conditions and therapeutic interventions

PKCα is a molecule with many functions that play an important role in cell survival and death to maintain cellular homeostasis. Alteration in the normal functioning of PKCα is responsible for the complicated etiology of many pathologies, including cancer, cardiovascular diseases, kidney complications, neurodegenerative diseases, diabetics, and many others. Several studies have been carried out over the years on this kinase's function, and regulation in normal physiology and pathological conditions. A lot of data with antithetical results have therefore accumulated over time to create a complex framework of physiological implications connected to the PKCα function that needs comprehensive elucidation. In light of this information, we critically analyze the multiple roles played by PKCα in basic cellular processes and their molecular mechanism during various pathological conditions. This review further discusses the current approaches to manipulating PKCα signaling amplitude in the patient's favour and proposed PKCα as a therapeutic target to reverse pathological states.

Signalling pathways in the osteogenic differentiation of periodontal ligament stem cells

Periodontal ligament stem cells (PDLSCs) have multidirectional differentiation potential and self-renewal abilities and are important seed cells for the regenerative repair of periodontal tissues. In recent years, many studies have identified multiple signalling pathways involved in regulating the osteogenic differentiation of PDLSCs in an inflammatory environment. In this article, we review the osteogenic differentiation of PDLSCs in an inflammatory environment in terms of signalling pathways and provide new ideas for the regenerative treatment of periodontal tissues.

Identification of immunodiagnostic blood biomarkers associated with spinal cord injury severity

Blood always shows some immune changes after spinal cord injury (SCI), and detection of such changes in blood may be helpful for diagnosis and treatment of SCI. However, studies to date on blood immune changes after SCI in humans are not comprehensive. Therefore, to obtain the characteristics of blood immune changes and immunodiagnostic blood biomarkers of SCI and its different grades, a human blood transcriptome sequencing dataset was downloaded and analyzed to obtain differentially expressed immune-related genes (DEIGs), related functions and signaling pathways related to SCI and its various grades. Characteristic biomarkers of SCI and its different grades were identified by using weighted gene coexpression network analysis (WGCNA) and least absolute shrinkage and selection operator (LASSO) logistic regression. Expression of biomarkers was verified through experiments. The area under the curve (AUC) of biomarkers was calculated to evaluate their diagnostic value, and differences in immune cell content were examined. In this study, 17 kinds of immune cells with different contents between the SCI group and healthy control (HC) group were identified, with 7 immune cell types being significantly increased. Differences in the content of immune cells between different grades of SCI and the HC group were also discovered. DEIGs were identified, with alteration in some immune-related signaling pathways, vascular endothelial growth factor signaling pathways, and axon guidance signaling pathways. The SCI biomarkers identified and those of American Spinal Injury Society Impairment Scale (AIS) A and AIS D of SCI have certain diagnostic sensitivity. Analysis of the correlation of immune cells and biomarkers showed that biomarkers of SCI, AIS A grade and AIS D grade correlated positively or negatively with some immune cells. CKLF, EDNRB, FCER1G, SORT1, and TNFSF13B can be used as immune biomarkers for SCI. Additionally, GDF11and HSPA1L can be used as biomarkers of SCI AIS A grade; PRKCA and CMTM2 can be used as biomarkers of the SCI AIS D grade. Detecting expression of these putative biomarkers and changes in related immune cells may be helpful for predicting the severity of SCI.

APOBEC3B Is Co-Expressed with PKCα/NF-κB in Oral and Oropharyngeal Squamous Cell Carcinomas

The enzymatic activity of APOBEC3B (A3B) has been implicated as a prime source of mutagenesis in head and neck squamous cell carcinoma (HNSCC). The expression of Protein Kinase C α (PKCα) and Nuclear Factor-κΒ p65 (NF-κΒ p65) has been linked to the activation of the classical and the non-canonical NF-κB signaling pathways, respectively, both of which have been shown to lead to the upregulation of A3B. Accordingly, the aim of the present study was to evaluate the expression of PKCα, NF-κΒ p65 and A3B in non-HPV related oral and oropharyngeal squamous cell carcinomas (SCC), by means of immunohistochemistry and in silico methods. PKCα was expressed in 29/36 (80%) cases of oral and oropharyngeal SCCs, with 25 (69%) cases showing a PKCα+/A3B+ phenotype and only 6/36 (17%) cases showing a PKCα-/A3B+ phenotype. Εxpression of NF-κB p65 was seen in 33/35 (94%) cases of oral and oropharyngeal SCCs, with 30/35 (86%) cases showing an NF-κB p65+/A3B+ phenotype and only 2/35 (6%) cases showing an NF-κB p65-/A3B+ phenotype. In addition, mRNA expression analysis, using the UALCAN database, revealed strong expression of all three genes. These findings indicate that the expression of A3B is associated with PKCα/NF-κB p65 expression and suggest a potential role for the PKC/NF-κB signaling pathway in the development of oral and oropharyngeal cancer.

Luteolin alleviates inorganic mercury-induced liver injury in quails by resisting oxidative stress and promoting mercury ion excretion

BackgroundInorganic mercury is a well-known toxic substance that can cause oxidative stress and liver damage. Luteolin (Lut) is a kind of natural antioxidant, which is widely found in plants. Therefore, we focused on exploring the alleviative effect of Lut on liver injury induced by mercuric chloride (HgCl₂), and the potential molecular mechanism of eliminating mercury ions in quails.Methods and resultsTwenty-one-day-old male quails were randomly split into four groups: control group, Lut group, HgCl₂ group, and HgCl₂ + Lut group. The test period was 12 weeks. The results showed that Lut could significantly ameliorate oxidative stress, the release of inflammatory factors, and liver damage caused by HgCl_2, and reduce the accumulation of Hg²⁺ in quail liver. Furthermore, Lut evidently increased the levels of protein kinase C α (PKCα), nuclear factor-erythroid-2-related factor 2 (Nrf2), and its downstream proteins, and inhibited nuclear factor-kappaB (NF-κB) production in the liver of quails treated by HgCl₂.ConclusionsTo sum up, our results suggest that Lut not only reduces the levels of oxidative stress and inflammation, but also promotes the excretion of Hg²⁺ by promoting the PKCα/Nrf2 signaling pathway to alleviate HgCl₂-induced liver injury in quails.

Protein Kinase C (PKC) Isozymes as Diagnostic and Prognostic Biomarkers and Therapeutic Targets for Cancer

Protein kinase C (PKC) is a large family of calcium- and phospholipid-dependent serine/threonine kinases that consists of at least 11 isozymes. Based on their structural characteristics and mode of activation, the PKC family is classified into three subfamilies: conventional or classic (cPKCs; α, βI, βII, and γ), novel or non-classic (nPKCs; δ, ε, η, and θ), and atypical (aPKCs; ζ, ι, and λ) (PKCλ is the mouse homolog of PKCι) PKC isozymes. PKC isozymes play important roles in proliferation, differentiation, survival, migration, invasion, apoptosis, and anticancer drug resistance in cancer cells. Several studies have shown a positive relationship between PKC isozymes and poor disease-free survival, poor survival following anticancer drug treatment, and increased recurrence. Furthermore, a higher level of PKC activation has been reported in cancer tissues compared to that in normal tissues. These data suggest that PKC isozymes represent potential diagnostic and prognostic biomarkers and therapeutic targets for cancer. This review summarizes the current knowledge and discusses the potential of PKC isozymes as biomarkers in the diagnosis, prognosis, and treatment of cancers.

PKCα and PKCδ: Friends and Rivals

PKC comprises a large family of serine/threonine kinases that share a requirement for allosteric activation by lipids. While PKC isoforms have significant homology, functional divergence is evident among subfamilies and between individual PKC isoforms within a subfamily. Here, we highlight these differences by comparing the regulation and function of representative PKC isoforms from the conventional (PKCα) and novel (PKCδ) subfamilies. We discuss how unique structural features of PKCα and PKCδ underlie differences in activation and highlight the similar, divergent, and even opposing biological functions of these kinases. We also consider how PKCα and PKCδ can contribute to pathophysiological conditions and discuss challenges to targeting these kinases therapeutically.

Thrombin Induces COX-2 and PGE2 Expression via PAR1/PKCalpha/MAPK-Dependent NF-kappaB Activation in Human Tracheal Smooth Muscle Cells

The inflammation of the airway and lung could be triggered by upregulation cyclooxygenase (COX)-2 and prostaglandin E₂ (PGE₂) induced by various proinflammatory factors. COX-2 induction by thrombin has been shown to play a vital role in various inflammatory diseases. However, in human tracheal smooth muscle cells (HTSMCs), how thrombin enhanced the levels of COX-2/PGE₂ is not completely characterized. Thus, in this study, the levels of COX-2 expression and PGE₂ synthesis induced by thrombin were determined by Western blot, promoter-reporter assay, real-time PCR, and ELISA kit. The various signaling components involved in the thrombin-mediated responses were differentiated by transfection with siRNAs and selective pharmacological inhibitors. The role of NF-κB was assessed by a chromatin immunoprecipitation (ChIP) assay, immunofluorescent staining, as well as Western blot. Our results verified that thrombin markedly triggered PGE₂ secretion via COX-2 upregulation which were diminished by the inhibitor of thrombin (PPACK), PAR1 (SCH79797), G_i/o protein (GPA2), G_q protein (GPA2A), PKCα (Gö6976), p38 MAPK (SB202190), JNK1/2 (SP600125), MEK1/2 (U0126), or NF-κB (helenalin) and transfection with siRNA of PAR1, G_qα, G_iα, PKCα, JNK2, p38, p42, or p65. Moreover, thrombin induced PAR1-dependent PKCα phosphorylation in HTSMCs. We also observed that thrombin induced p38 MAPK, JNK1/2, and p42/p44 MAPK activation through a PAR1/PKCα pathway. Thrombin promoted phosphorylation of NF-κB p65, leading to nuclear translocation and binding to the COX-2 promoter element to enhance promoter activity, which was reduced by Gö6976, SP600125, SB202190, or U0126. These findings supported that COX-2/PGE₂ expression triggered by thrombin was engaged in PAR1/G_q or G_i/o/PKCα/MAPK-dependent NF-κB activation in HTSMCs.

Type-2 diabetic rat heart: The effect of kolaviron on mTOR-1, P70S60K, PKC-α, NF-kB, SOD-2, NRF-2, eNOS, AKT-1, ACE, and P38 MAPK gene expression profile

It has been established that genetic factors partially contribute to type-2 diabetes and vascular disease development. This study determined the effect of kolaviron on the expression profile of genes associated with the insulin signaling pathway and involved in regulating glucose and lipid metabolism, oxidative stress, inflammation, vascular functions, pro-survival and the apoptosis pathway in the heart of type-2 diabetic rats. After induction and confirmation of type-2 diabetes seven days after, the rats were treated with kolaviron for twenty-eight days before being euthanized. Organs were harvested and stored at - 80 °C in a biofreezer. Total RNA was extracted from the ventricle, reverse transcribed to cDNA followed by a real-time quantitative polymerase chain reaction (RT-qPCR) analysis of the expression of mTOR-1, P70S60K, PKC-α, NF-kB, SOD-2, NRF-2, eNOS, AKT-1, ACE, p38 MAPK and the reference gene (GAPDH), after which they were normalized/standardized. The results show an increase in the relative mRNA expression of mTOR/P70S60K/PKCα /P38MAPK/NF-KB/ACE and a decrease in the relative mRNA expression of NRF2/SOD/AKT/eNOS in the heart of the diabetic rats. Nevertheless, kolaviron modulated the expression profile of these genes, which suggest a therapeutic effect and target for vascular dysfunction and complications in type-2 diabetes through the activation of the NRF-2/AKT-1/eNOS signaling pathway and suppression of the NF-kB/PKC signaling pathway.

Upregulation of UGT1A1 expression by ursolic acid and oleanolic acid via the inhibition of the PKC/NF-κB signaling pathway

BACKGROUND

Isomeric ursolic acid (UA) and oleanolic acid (OA) compounds have recently garnered great attention due to their biological effects. Previously, it had been shown that UA and OA can exert important pharmacological action via the protein kinase C (PKC) and nuclear factor-κB (NF-κB) signaling, and that they can induce the expression of UDP-glucuronosyltransferase 1A1 (UGT1A1) in HepG2 cells. This study aims to investigate the role of PKC/NF-κB signaling in regulating the expression of UGT1A1 and examine how UA and OA induce UGT1A1 based on this signaling pathway.

METHODS

HepG2 cells, hp65-overexpressed HepG2 cell and lentivirus-hp65-shRNA silenced HepG2 cells were stimulated with PKC/NF-κB specific agonists and inhibitors for 24 h in the presence or absence of UA and OA. The expression of UGT1A1, PKC, and NF-κB were determined by qRT-PCR, western blot, and dual-luciferase reporter gene assays.

RESULTS

PKC/NF-κB activation downregulates UGT1A1 expression. This effect is countered by UA and OA treatment. Phorbol 12-myristate 13-acetate (PMA) and lipopolysaccharide (LPS), the agonists of PKC and NF-κB signaling, respectively, significantly inhibit hp65-mediated UGT1A1 luciferase activity. UA, OA, and the PKC/NF-κB inhibitors suppress this effect. PMA and LPS do not affect UGT1A1 activity in p65-silenced HepG2 cells; however, UA and OA mildly influence UGT1A1 expression in these cells.

CONCLUSION

The activation of PKC/NF-κB signaling can significantly downregulate UGT1A1 expression. By inhibiting the PKC/NF-κB signaling pathway, UA and OA promote UGT1A1 expression in HepG2 cells.

Identification of Activated Protein Kinase Cα (PKCα) in the Urine of Orthotopic Bladder Cancer Xenograft Model as a Potential Biomarker for the Diagnosis of Bladder Cancer

Bladder cancer has a high recurrence rate; therefore, frequent and effective monitoring is essential for disease management. Cystoscopy is considered the gold standard for the diagnosis and continuous monitoring of bladder cancer. However, cystoscopy is invasive and relatively expensive. Thus, there is a need for non-invasive, relatively inexpensive urinary biomarker-based diagnoses of bladder cancer. This study aimed to investigate the presence of activated protein kinase Cα (PKCα) in urine samples and the possibility of PKCα as a urinary biomarker for bladder cancer diagnosis. Activated PKCα was found to be present at higher levels in bladder cancer tissues than in normal bladder tissues. Furthermore, high levels of activated PKCα were observed in urine samples collected from orthotopic xenograft mice carrying human bladder cancer cells compared to urine samples from normal mice. These results suggest that activated PKCα can be used as a urinary biomarker to diagnose bladder cancer. To the best of our knowledge, this is the first report describing the presence of activated PKCα in the urine of orthotopic xenograft mice.

The Antitumor Effects of Britanin on Hepatocellular Carcinoma Cells and its Real-Time Evaluation by In Vivo Bioluminescence Imaging

BACKGROUND

Hepatocellular carcinoma is cancer with many new cases and the highest mortality rate. Chemotherapy is the most commonly used method for the clinical treatment of hepatocellular carcinoma. Natural products have become clinically important chemotherapeutic drugs due to their great potential for pharmacological development. Many sesquiterpene lactone compounds have been proven to have antitumor effects on hepatocellular carcinoma.

OBJECTIVE

Britanin is a sesquiterpene lactone compound that can be considered for the treatment of hepatocellular carcinoma. The present study aimed to investigate the antitumor effect of britanin.

METHODS

BEL 7402 and HepG2 cells were used to study the cytotoxicity and antitumor effects of britanin. Preliminary studies on the nuclear factor kappa B pathway were conducted by western blot analysis. A BEL 7402-luc subcutaneous tumor model was established for the in vivo antitumor studies of britanin. In vivo bioluminescence imaging was conducted to monitor changes in tumor size.

RESULTS

The results of the cytotoxicity analysis showed that the IC50 values for britanin in BEL 7402 and HepG2 cells were 2.702μM and 6.006μM, respectively. The results of the colony formation demonstrated that the number of cells in a colony was reduced significantly after britanin treatment. And the results of transwell migration assays showed that the migration ability of tumor cells was significantly weakened after treatment with britanin. Tumor size measurements and staining results showed that tumor size was inhibited after britanin treatment. The western blot analysis results showed the inhibition of p65 protein expression and reduced the ratio of Bcl-2/Bax after treatment.

CONCLUSION

A series of in vitro and in vivo experiments demonstrated that britanin had good antitumor effects and provided an option for hepatocellular carcinoma treatment.

6,6'-Dihydroxythiobinupharidine (DTBN) Purified from Nuphar lutea Leaves Is an Inhibitor of Protein Kinase C Catalytic Activity

Water lily (Nuphar) bioactive extracts have been widely used in traditional medicine owing to their multiple applications against human ailments. Phyto-active Nuphar extracts and their purified and synthetic derivatives have attracted the attention of ethnobotanists and biochemists. Here, we report that 6,6'-dihydroxythiobinupharidine (DTBN), purified from extracts of Nuphar lutea (L.) Sm. leaves, is an effective inhibitor of the kinase activity of members of the protein kinase C (PKC) family using in vitro and in silico approaches. We demonstrate that members of the conventional subfamily of PKCs, PKCα and PKCγ, were more sensitive to DTBN inhibition as compared to novel or atypical PKCs. Molecular docking analysis demonstrated the interaction of DTBN, with the kinase domain of PKCs depicting the best affinity towards conventional PKCs, in accordance with our in vitro kinase activity data. The current study reveals novel targets for DTBN activity, functioning as an inhibitor for PKCs kinase activity. Thus, this and other data indicate that DTBN modulates key cellular signal transduction pathways relevant to disease biology, including cancer.

The complexities of PKCα signaling in cancer

Protein kinase C α (PKCα) is a ubiquitously expressed member of the PKC family of serine/threonine kinases with diverse functions in normal and neoplastic cells. Early studies identified anti-proliferative and differentiation-inducing functions for PKCα in some normal tissues (e.g., regenerating epithelia) and pro-proliferative effects in others (e.g., cells of the hematopoietic system, smooth muscle cells). Additional well documented roles of PKCα signaling in normal cells include regulation of the cytoskeleton, cell adhesion, and cell migration, and PKCα can function as a survival factor in many contexts. While a majority of tumors lose expression of PKCα, others display aberrant overexpression of the enzyme. Cancer-related mutations in PKCα are uncommon, but rare examples of driver mutations have been detected in certain cancer types (e. g., choroid gliomas). Here we review the role of PKCα in various cancers, describe mechanisms by which PKCα affects cancer-related cell functions, and discuss how the diverse functions of PKCα contribute to tumor suppressive and tumor promoting activities of the enzyme. We end the discussion by addressing mutations and expression of PKCα in tumors and the clinical relevance of these findings.

The Prophylactic Activity of Punica granatum L. mesocarp Protects Preadipocytes against Ribosylated BSA-Induced Toxicity

OBJECTIVE

It was aimed at comparing the glycating capacities of glucose and ribose in bovine serum albumin (BSA) and anti-glycation activity of pomegranate mesocarp extract (PME). The protective mechanism of PME against ribosylated BSA (BSA_RIB)-induced toxicity was also investigated.

METHODS

BSA was incubated with glucose or ribose in the presence or absence of PME for 15 days. In preadipocytes pretreated with PME, cell viability, ROS production, lipid peroxidation and mitochondrial membrane potential were investigated following 1, 6, 12, 18 and 24 h exposure to BSA_RIB. Nuclear translocation of NFκB was assessed at 1 h and 24 h of BSA_RIB insult. Accumulation of oxidized proteins, activities of intrinsic antioxidant enzymes and IL-6 secretion were also determined after 24 h exposure to BSA_RIB.

RESULTS

Ribose was a harsher glycating agent as compared to glucose and PME showed strong anti-glycation activity by suppressing (P < 0.05) the increase in levels of fluorescent AGEs, Amadori products, protein carbonyl and advanced oxidation protein products (AOPP). In preadipocytes, BSA_RIB potentiated pro-apoptotic activity by inhibiting the nuclear translocation of NFκB. BSA_RIB induced a time dependent decrease in cell viability, which was significantly suppressed (P < 0.05) by PME. The extract also significantly reduced (P < 0.05) the time dependent increase in ROS level and associated lipid peroxidation as well as loss in mitochondrial membrane potential caused by BSA_RIB. PME also counteracted the BSA_RIB-induced accumulation of oxidized proteins, decrease in intrinsic antioxidant activity and IL-6 over-secretion.

CONCLUSIONS

PME showed anti-glycation activity and afforded protection against BSA_RIB-induced toxicity, oxidative stress and inflammation in preadipocytes.

Bioactive Ether Lipids: Primordial Modulators of Cellular Signaling

The primacy of lipids as essential components of cellular membranes is conserved across taxonomic domains. In addition to this crucial role as a semi-permeable barrier, lipids are also increasingly recognized as important signaling molecules with diverse functional mechanisms ranging from cell surface receptor binding to the intracellular regulation of enzymatic cascades. In this review, we focus on ether lipids, an ancient family of lipids having ether-linked structures that chemically differ from their more prevalent acyl relatives. In particular, we examine ether lipid biosynthesis in the peroxisome of mammalian cells, the roles of selected glycerolipids and glycerophospholipids in signal transduction in both prokaryotes and eukaryotes, and finally, the potential therapeutic contributions of synthetic ether lipids to the treatment of cancer.

Aza-PBHA, a potent histone deacetylase inhibitor, inhibits human gastric-cancer cell migration via PKCα-mediated AHR-HDAC interactions

Recently, histone deacetylase inhibitors (HDACi) have become widely used in anti-cancer treatment; however, due to acquired drug resistance and their relatively low specificity, they are largely ineffective against late-stage cancer. Thus, it is critical to elucidate the molecular mechanisms underlying these issues, so as to identify novel therapeutic targets to prevent late-stage cancer progression and resistance acquisition. The present study investigated the Aryl hydrocarbon receptor (AHR), that has been shown to mediate histone acetylation by regulating histone deacetylase (HDAC) activity during HDACi treatment in human gastric-cancer cell lines (i.e. AGS and NCI-N87 cells). The potent HDACi, Aza-PBHA, was thus shown to upregulate AHR expression in both AGS and NCI-N87 cell lines, and to increase histone acetylation levels by facilitating AHR/HDAC interactions. Conversely, AHR knockdown increased HDAC activity. Aza-PBHA also increased PKCα phosphorylation and membrane translocation; however, interestingly, PKCα inhibition reduced the Aza-PBHA-increased AHR and histone acetylation levels, and inhibited the formation of the AHR/HDAC complex, likely upregulating Aza-PBHA-inhibited cell migration. Thus, our results suggest that Aza-PBHA treatment increased AHR levels to suppress HDAC activity, and inhibited cell migration by activating PKCα activation. These findings support the use of drugs to control AHR-related epigenetic regulation as a promising potential method to prevent acquired resistance to cancer treatments.

miR-506 contributes to malignancy of cutaneous squamous cell carcinoma via targeting of P65 and LAMC1

Previous research has shown that microRNA 506 (miR-506) functions as an essential modulator in the development of many biological reactions, including multiple cancers. However, its involvement in cutaneous squamous cell carcinoma (CSCC) has been rarely reported. In the present work, we investigated the molecular mechanism and function of miR-506 in the regulation of CSCC cell viability and metastasis (migration and invasion). We observed that miR-506 expression was upregulated in both CSCC tissues and cell lines, and that decreased miR-506 expression led to repressed tumorigenesis in CSCC cells. Furthermore, flow cytometry revealed that the depletion of miR-506 resulted in decreased proliferation and increased apoptotic levels in CSCC cells. Meanwhile, it was found that miR-506 decreased CSCC cell migration and invasion in vitro. The dual-luciferase reporter assay also revealed that miR-506 targets the 3'-UTRs of p65 and Laminin C1 (LAMC1) for silencing. Silencing of p65 expression counteracted the pro-apoptotic influence of miR-506 depletion in CSCC cells, while inhibition of LAMC1 expression restored the migration and invasion properties of the CSCC cells. Therefore, the results provide evidence for the need to probe the biological and molecular mechanisms behind the development and progression of CSCC and may lead to novel treatment CSCC strategies.

The m6A methyltransferase METTL3 promotes bladder cancer progression via AFF4/NF-κB/MYC signaling network

N⁶-methyladenosine (m6A) is the most abundant modification in eukaryotic messenger RNAs (mRNAs), and plays important roles in many bioprocesses. However, its functions in bladder cancer (BCa) remain elusive. Here, we discovered that methyltransferase-like 3 (METTL3), a major RNA N⁶-adenosine methyltransferase, was significantly up-regulated in human BCa. Knockdown of METTL3 drastically reduced BCa cell proliferation, invasion, and survival in vitro and tumorigenicity in vivo. On the other hand, overexpression of METTL3 significantly promoted BCa cell growth and invasion. Through transcriptome sequencing, m⁶A sequencing and m⁶A methylated RNA immuno-precipitation quantitative reverse-transcription polymerase chain reaction, we revealed the profile of METTL3-mediated m⁶A modification in BCa cells for the first time. AF4/FMR2 family member 4 (AFF4), two key regulators of NF-κB pathway (IKBKB and RELA) and MYC were further identified as direct targets of METTL3-mediated m⁶A modification. In addition, we showed that besides NF-κB, AFF4 binds to the promoter of MYC and promotes its expression, implying a novel multilevel regulatory network downstream of METTL3. Our results uncovered an AFF4/NF-κB/MYC signaling network operated by METTL3-mediated m6A modification and provided insight into the mechanisms of BCa progression.

Grape Seed Proanthocyanidin Extract Alleviates AflatoxinB₁-Induced Immunotoxicity and Oxidative Stress via Modulation of NF-κB and Nrf2 Signaling Pathways in Broilers

Aflatoxin B₁ (AFB₁) is a widely spread mycotoxin contaminates food and feed, causing severe oxidative stress damages and immunotoxicity. Grape seed proanthocyanidin (GSPE), a natural antioxidant with wide range of pharmacological and medicinal properties. The goal of the present study was to investigate the protective effects of GSPE against AFB₁-induced immunotoxicity and oxidative stress via NF-κB and Nrf2 signaling pathways in broiler chickens. For the experiment, 240 one-day old Cobb chicks were allocated into four dietary treatment groups of six replicates (10 birds per replicate): 1. Basal diet (control); 2. Basal diet + AFB₁ 1mg/kg contaminated corn (AFB₁); 3. Basal diet + GSPE 250 mg/kg (GSPE); 4. Basal diet + AFB₁ 1 mg/kg + GSPE 250 mg/kg (AFB₁ + GSPE). The results showed that GSPE significantly decreased serum inflammatory cytokines TNF-α, IFN-γ, IL-1β, IL-10, and IL-6 induced by AFB₁. Similarly, GSPE + AFB₁ treated group revealed a significant decrease in mRNA expressions of pro-inflammatory cytokines (TNF-α, IFN-γ, IL-1β, and IL-6) in the splenic tissue compared to the AFB₁ treatment group. In addition, western blotting results manifested that GSPE treatment normalized the phosphorylation of nuclear factor kappa B (p65) and the degradation of IκBα protein induced by AFB₁. Furthermore, GSPE enhanced the antioxidant defense system through activating the nuclear factor-erythroid-2-related factor (Nrf2) signaling pathway. The mRNA and protein expression level of Nrf2 and its down streaming associated genes were noted up-regulated by the addition of GSPE, and down-regulated in the AFB₁ group. Taken together, GSPE alleviates AFB₁-induced immunotoxicity and oxidative damage by inhibiting the NF-κB and activating the Nrf2 signaling pathways in broiler chickens. Conclusively, our results suggest that GSPE could be considered as a potential natural agent for the prevention of AFB₁-induced immunotoxicity and oxidative damage.

Theaflavin alleviates inflammatory response and brain injury induced by cerebral hemorrhage via inhibiting the nuclear transcription factor kappa β-related pathway in rats

OBJECTIVE

Intracerebral hemorrhage (ICH) is one of the most common acute cerebrovascular diseases with high mortality. Numerous studies have shown that inflammatory response played an important role in ICH-induced brain injury. Theaflavin (TF) extracted from black tea has various biological functions including anti-inflammatory activity. In this study, we investigated whether TF could inhibit ICH-induced inflammatory response in rats and explored its mechanism.

MATERIALS AND METHODS

ICH rat models were induced with type VII collagenase and pretreated with TF by gavage in different doses (25 mg/kg-100 mg/kg). Twenty-four hours after ICH attack, we evaluated the rats' behavioral performance, the blood-brain barrier (BBB) integrity, and the formation of cerebral edema. The levels of reactive oxygen species (ROS) and inflammatory cytokines were examined by 2',7'-dichlorofluorescin diacetate and enzyme-linked immunosorbent assay. Nissl staining and transferase dUTP nick end labeling (TUNEL) were aimed to detect the neuron loss and apoptosis, the mechanism of which was explored by Western blot.

RESULTS

It was found that in the pretreated ICH rats TF significantly alleviated the behavioral defects, protected BBB integrity, and decreased the formation of cerebral edema and the levels of ROS as well as inflammatory cytokines (including interleukin-1 beta [IL-1β], IL-18, tumor nectosis factor-alpha, interferon-γ, transforming growth factor beta, and (C-X-C motif) ligand 1 [CXCL1]). Nissl staining and TUNEL displayed TF could protect against the neuron loss and apoptosis via inhibiting the activation of nuclear transcription factor kappa-β-p65 (NF-κβ-p65), caspase-1, and IL-1β. We also found that phorbol 12-myristate 13-acetate, a nonspecific activator of NF-κβ-p65, weakened the positive effect of TF on ICH-induced neural defects and neuron apoptosis by upregulating NF-κβ-related signaling pathway.

CONCLUSION

TF could alleviate ICH-induced inflammatory responses and brain injury in rats via inhibiting NF-κβ-related pathway, which may provide a new way for the therapy of ICH.

Induction of nerve growth factor by phorbol 12-myristate 13-acetate is dependent upon the mitogen activated protein kinase pathway

Several small molecules have been identified that induce glial cells to synthesize and secrete nerve growth factor (NGF), a critical neurotrophin that supports neuronal growth and survival, and as such show promise in the development of drugs for the chemoprevention of Alzheimer's disease. To map the signal transduction cascade leading to NGF synthesis and secretion, cultured human glial cells were stimulated by phorbol 12-myristate 13-acetate (PMA), an agonist of Protein Kinase C. Changes in intracellular protein phosphorylation states were evaluated by reverse phase protein microarrays (RPPA), selectively screening over 130 protein endpoints. Of these, 55 proteins showed statistically significant changes in phosphorylation state due to cellular exposure to PMA. A critical signal transduction pathway was identified, and subsequent validation by ELISA and qPCR revealed that the signaling proteins Raf, MEK, ERK, and the signal transduction factor CREB are all essential to the upregulation of NGF gene expression by PMA. Additionally, members of the RSK family of kinases appear to be involved in glial secretion (exocytosis) of the NGF protein. Furthermore, through RPPA, the effects of PMA on apoptosis signaling events and cell proliferation were differentiated from the pathway to NGF upregulation. Overall, this study reveals potential protein targets for the rational design of Alzheimer's therapeutics.

Nuclear Factor-κB Promotes Urothelial Tumorigenesis and Cancer Progression via Cooperation with Androgen Receptor Signaling

We investigated the role of NF-κB in the development and progression of urothelial cancer as well as cross-talk between NF-κB and androgen receptor (AR) signals in urothelial cells. Immunohistochemistry in surgical specimens showed that the expression levels of NF-κB/p65 (P = 0.015)/phospho-NF-κB/p65 (P < 0.001) were significantly elevated in bladder tumors, compared with those in nonneoplastic urothelial tissues. The rates of phospho-NF-κB/p65 positivity were also significantly higher in high-grade (P = 0.015)/muscle-invasive (P = 0.033) tumors than in lower grade/non-muscle-invasive tumors. Additionally, patients with phospho-NF-κB/p65-positive muscle-invasive bladder cancer had significantly higher risks of disease progression (P < 0.001) and cancer-specific mortality (P = 0.002). In immortalized human normal urothelial SVHUC cells stably expressing AR, NF-κB activators and inhibitors accelerated and prevented, respectively, their neoplastic transformation induced by a chemical carcinogen 3-methylcholanthrene. Bladder tumors were identified in 56% (mock), 89% (betulinic acid), and 22% (parthenolide) of N-butyl-N-(4-hydroxybutyl)nitrosamine-treated male C57BL/6 mice at 22 weeks of age. NF-κB activators and inhibitors also significantly induced and reduced, respectively, cell proliferation/migration/invasion of AR-positive bladder cancer lines, but not AR-knockdown or AR-negative lines, and their growth in xenograft-bearing mice. In both nonneoplastic and neoplastic urothelial cells, NF-κB activators/inhibitors upregulated/downregulated, respectively, AR expression, whereas AR overexpression was associated with increases in the expression levels of NF-κB/p65 and phospho-NF-κB/p65. Thus, NF-κB appeared to be activated in bladder cancer, which was associated with tumor progression. NF-κB activators/inhibitors were also found to modulate tumorigenesis and tumor outgrowth in AR-activated urothelial cells. Accordingly, NF-κB inhibition, together with AR inactivation, has the potential of being an effective chemopreventive and/or therapeutic approach for urothelial carcinoma. Mol Cancer Ther; 17(6); 1303-14. ©2018 AACR.

Anti-Inflammatory and Immune Regulatory Actions of Naja naja atra Venom

Naja naja atra venom (NNAV) is composed of various proteins, peptides, and enzymes with different biological and pharmacological functions. A number of previous studies have reported that NNAV exerts potent analgesic effects on various animal models of pain. The clinical studies using whole venom or active components have confirmed that NNAV is an effective and safe medicine for treatment of chronic pain. Furthermore, recent studies have demonstrated that NNAV has anti-inflammatory and immune regulatory actions in vitro and in vivo. In this review article, we summarize recent studies of NNAV and its components on inflammation and immunity. The main new findings in NNAV research show that it may enhance innate and humoral immune responses while suppressing T lymphocytes-mediated cellular immunity, thus suggesting that NNAV and its active components may have therapeutic values in the treatment of inflammatory and autoimmune diseases.

PKCδ reveals a tumor promoter function by promoting cell proliferation and migration in somatotropinomas

Protein kinase C δ (PKCδ), a subtype of PKC family, has been recognized as a tumor promoter or suppressor depending on different tissue specificities in various tumor types. However, the effects of PKCδ on somatotropinomas are poorly understood. This study aims to explore the precise role of PKCδ in promoting tumor progression in somatotropinomas. In the present study, we examined the expression levels of PKCδ in clinical specimens of human somatotropinomas to show that PKCδ overexpression correlated with invasive properties of somatotropinomas. Furthermore, we employed rat anterior pituitary GH3 cells as the experiment model to demonstrate that PKCδ activation by PKC agonist (Phorbol-12-myristate-13-acetate, PMA) significantly promoted the proliferation and migration potential of GH3 cells, and these effects could be abolished following PKCδ inhibition by specific inhibitor Rottlerin. Mechanistically, PKCδ activated ERK1/2 signaling, which was responsible for PKCδ-induced promotion of GH3 cell proliferation and migration. Taken together, our results indicated that PKCδ functions as a tumor promoter by promoting cell proliferation and migration in somatotropinomas.