A novel moonlight function of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) for immunomodulation

Newborns with Favourable Outcomes after Perinatal Asphyxia Have Upregulated Glucose Metabolism-Related Proteins in Plasma

Hypoxic-ischaemic encephalopathy (HIE) is an important cause of morbidity and mortality globally. Although mild therapeutic hypothermia (TH) may improve outcomes in selected babies, the mechanism of action is not fully understood. A proteomics discovery study was carried out to analyse proteins in the plasma of newborns with HIE. Proteomic analysis of plasma from 22 newborns with moderate-severe HIE that had initially undergone TH, and relative controls including 10 newborns with mild HIE who did not warrant TH and also cord blood from 10 normal births (non-HIE) were carried out using the isobaric Tandem Mass Tag (TMT®) 10plexTM labelling with tandem mass spectrometry. A total of 7818 unique peptides were identified in all TMT10plexTM samples, translating to 3457 peptides representing 405 proteins, after applying stringent filter criteria. Apart from the unique protein signature from normal cord blood, unsupervised analysis revealed several significantly regulated proteins in the TH-treated moderate-severe HIE group. GO annotation and functional clustering revealed various proteins associated with glucose metabolism: the enzymes fructose-bisphosphate aldolase A, glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate mutase 1, phosphoglycerate kinase 1, and pyruvate kinase PKM were upregulated in newborns with favourable (sHIE+) outcomes compared to newborns with unfavourable (sHIE-) outcomes. Those with favourable outcomes had normal MR imaging or mild abnormalities not predictive of adverse outcomes. However, in comparison to mild HIE and the sHIE- groups, the sHIE+ group had the additional glucose metabolism-related enzymes upregulated, including triosephosphate isomerase, α-enolase, 6-phosphogluconate dehydrogenase, transaldolase, and mitochondrial glutathione reductase. In conclusion, our plasma proteomic study demonstrates that TH-treated newborns with favourable outcomes have an upregulation in glucose metabolism. These findings may open new avenues for more effective neuroprotective therapy.

Subcutaneous Streptococcus dysgalactiae GAPDH vaccine in mice induces a proficient innate immune response

BACKGROUND

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) on the surface of Streptococcus dysgalactiae, coded with gapC, is a glycolytic enzyme that was reported to be a moonlighting protein and virulence factor.

OBJECTIVE

This study assessed GAPDH as a potential immunization candidate protein to prevent streptococcus infections.

METHODS

Mice were vaccinated subcutaneously with recombinant GAPDH and challenged with S. dysgalactiae in vivo. They were then evaluated using histological methods. rGAPDH of mouse bone marrow-derived dendritic cells (BMDCs) was evaluated using immunoblotting, reverse transcription quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay methods.

RESULTS

Vaccination with rGAPDH improved the survival rates and decreased the bacterial burdens in the mammary glands compared to the control group. The mechanism by which rGAPDH vaccination protects against S. dysgalactiae was investigated. In vitro experiments showed that rGAPDH boosted the generation of interleukin-10 and tumor necrosis factor-α. Treatment of BMDCs with TAK-242, a toll-like receptor 4 inhibitor, or C29, a toll-like receptor 2 inhibitor, reduced cytokines substantially, suggesting that rGAPDH may be a potential ligand for both TLR2 and TLR4. Subsequent investigations showed that rGAPDH may activate the phosphorylation of MAPKs and nuclear factor-κB.

CONCLUSIONS

GAPDH is a promising immunization candidate protein for targeting virulence and enhancing immune-mediated protection. Further investigations are warranted to understand the mechanisms underlying the activation of BMDCs by rGAPDH in a TLR2- and TLR4-dependent manner and the regulation of inflammatory cytokines contributing to mastitis pathogenesis.

Overexpression of miR-4669 Enhances Tumor Aggressiveness and Generates an Immunosuppressive Tumor Microenvironment in Hepatocellular Carcinoma: Its Clinical Value as a Predictive Biomarker

Accumulating evidence suggests the involvement of tumor-derived exosomes in the development and recurrence of hepatocellular carcinoma (HCC). We previously identified miR-4669 as a highly expressed microRNA in circulating exosomes obtained from patients with post-transplant HCC recurrence. This study aimed to explore how overexpression of miR-4669 affects HCC development and recurrence. The impact of miR-4669 overexpression in Hep3B cells on tumor cell behavior and the tumor microenvironment was evaluated in vitro. In addition, the clinical value of exosomal miR-4669 for the prediction of treatment response to HCC downstaging therapies and following post-transplant HCC recurrence was explored. Overexpression of miR-4669 enhanced migration ability and led to acquired sorafenib resistance with an elevation of sirtuin 1 and long noncoding RNA associated with microvascular invasion. Active release of tumor-derived exosomes and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) contributed to generating an immunosuppressive tumor microenvironment through the induction of M2 macrophage polarization. The retrospective analysis demonstrated the clinical value of exosomal miR-4669 for predicting treatment response to HCC downstaging therapies and for risk assessment of post-transplant HCC recurrence. In summary, the present data demonstrate the impact of exosomal miR-4669 on HCC recurrence through the enhancement of tumor aggressiveness and generation of an immunosuppressive tumor microenvironment.

Effects of Dietary Alpha-Lipoic Acid on Growth Performance, Serum Biochemical Indexes, Liver Antioxidant Capacity and Transcriptome of Juvenile Hybrid Grouper (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂)

We aimed to investigate the effects of dietary alpha-lipoic acid (α-LA) on the growth performance, serum biochemical indexes, liver morphology, antioxidant capacity, and transcriptome of juvenile hybrid groupers (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂). Four experimental diets supplemented with 0 (SL0), 0.4 (L1), 0.6 (L2), and 1.2 (L3) g/kg α-LA were formulated and fed to three replicates of juvenile hybrid grouper (24.06 ± 0.15 g) for 56 d. The results indicated that dietary 0.4 and 0.6 g/kg α-LA significantly decreased the weight gain rate in juvenile hybrid groupers. Compared with SL0, the content of total protein in the serum of L1, L2, and L3 increased significantly, and alanine aminotransferase decreased significantly. The content of albumin in the serum of L3 increased significantly, and triglyceride, total cholesterol, and aspartate aminotransferase decreased significantly. In addition, the hepatocyte morphology in L1, L2, and L3 all showed varying degrees of improvement, and the activities of glutathione peroxidase and superoxide dismutase in the liver of L2 and L3 were significantly increased. A total of 42 differentially expressed genes were screened in the transcriptome data. KEGG showed that a total of 12 pathways were significantly enriched, including the pathway related to immune function and glucose homeostasis. The expression of genes (ifnk, prl4a1, prl3b1, and ctsl) related to immune were significantly up-regulated, and the expressions of gapdh and eno1 genes related to glucose homeostasis were significantly down-regulated and up-regulated, respectively. In summary, dietary supplementation of 0.4 and 0.6 g/kg α-LA inhibited the growth performance of juvenile hybrid groupers. A total of 1.2 g/kg α-LA could reduce the blood lipid level, improve hepatocyte damage, and increase the hepatic antioxidant enzyme activity. Dietary α-LA significantly affected the pathway related to immune function and glucose homeostasis.

Allogenic Adipose-Derived Stem Cells in Diabetic Foot Ulcer Treatment: Clinical Effectiveness, Safety, Survival in the Wound Site, and Proteomic Impact

Although encouraging results of adipose-derived stem cell (ADSC) use in wound healing are available, the mechanism of action has been studied mainly in vitro and in animals. This work aimed to examine the safety and efficacy of allogenic ADSCs in human diabetic foot ulcer treatment, in combination with the analyses of the wound. Equal groups of 23 participants each received fibrin gel with ADSCs or fibrin gel alone. The clinical effects were assessed at four time points: days 7, 14, 21 and 49. Material collected during debridement from a subset of each group was analyzed for the presence of ADSC donor DNA and proteomic changes. The reduction in wound size was greater at all subsequent visits, significantly on day 21 and 49, and the time to 50% reduction in the wound size was significantly shorter in patients who received ADSCs. Complete healing was achieved at the end of the study in seven patients treated with ADSCs vs. one treated without ADSCs. One week after ADSC application, 34 proteins significantly differentiated the material from both groups, seven of which, i.e., GAPDH, CAT, ACTN1, KRT1, KRT9, SCL4A1, and TPI, positively correlated with the healing rate. We detected ADSC donor DNA up to 21 days after administration. We confirmed ADSC-related improvement in wound healing that correlated with the molecular background, which provides insights into the role of ADSCs in wound healing-a step toward the development of cell-based therapies.

Immunomodulatory effects of extracellular glyceraldehyde 3-phosphate dehydrogenase of exopolysaccharide-producing Lactiplantibacillus plantarum JCM 1149

Probiotic lactic acid bacteria evoke immunomodulatory effects in the host; however, the reasons for the different effects of various species and strains remain to be elucidated. To clarify the critical immunomodulatory components and impact of exopolysaccharide (EPS) in Lactiplantibacillus plantarum, 11 types of L. plantarum strains were compared for the production of EPS, inflammatory cytokines, interleukin-6 and -12, and the anti-inflammatory cytokine, interleukin-10, from THP-1 differentiated dendritic cells. EPS in the fermented medium correlated with cytokine-inducing activities. L. plantarum JCM 1149, with the highest production of EPS, also induced interleukin-6, -10, and -12 among the 11 tested strains. Notably, the cytokine-producing activities overlapped with the protein fraction in gel filtration chromatography but not with EPS, which has been reported to exert immunomodulatory effects. The 41 kDa protein that coexisted with EPS was purified as a major active component and identified as glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a known moonlighting protein. GAPDH secretion was reduced when EPS synthesis inhibitors were added to the culture medium. RNA sequencing of GAPDH-treated THP-1 cells revealed an up-regulation in the expression of genes involved in transcriptional regulation, cell surface receptor signalling, immune response, and matrix components. Here, we report, to our knowledge for the first time, that the cell surface-associated L. plantarum GAPDH plays a crucial role in cytokine production in THP-1 cells, but EPS with less activity may help GAPDH secretion.

Moonlighting glyceraldehyde-3-phosphate dehydrogenase (GAPDH) protein of Lactobacillus gasseri attenuates allergic asthma via immunometabolic change in macrophages

BACKGROUND

The extra-intestinal effects of probiotics for preventing allergic diseases are well known. However, the probiotic components that interact with host target molecules and have a beneficial effect on allergic asthma remain unknown. Lactobacillus gasseri attenuates allergic airway inflammation through the activation of peroxisome proliferator- activated receptor γ (PPARγ) in dendritic cells. Therefore, we aimed to isolate and investigate the immunomodulatory effect of the PPARγ activation component from L. gasseri.

METHODS

Culture supernatants of L. gasseri were fractionated and screened for the active component for allergic asthma. The isolated component was subjected to in vitro functional assays and then cloned. The crystal structure of this component protein was determined using X-ray crystallography. Intrarectal inoculation of the active component-overexpressing Clear coli (lipopolysaccharide-free Escherichia coli) and intraperitoneal injection of recombinant component protein were used in a house dust mite (HDM)-induced allergic asthma mouse model to investigate the protective effect. Recombinant mutant component proteins were assayed, and their structures were superimposed to identify the detailed mechanism of alleviating allergic inflammation.

RESULTS

A moonlighting protein, glycolytic glyceraldehyde 3-phosphate dehydrogenase (GAPDH), LGp40, that has multifunctional effects was purified from cultured L. gasseri, and the crystal structure was determined. Both intrarectal inoculation of LGp40-overexpressing Clear coli and intraperitoneal administration of recombinant LGp40 protein attenuated allergic inflammation in a mouse model of allergic asthma. However, CDp40, GAPDH isolated from Clostridium difficile did not possess this anti-asthma effect. LGp40 redirected allergic M2 macrophages toward the M1 phenotype and impeded M2-prompted Th2 cell activation through glycolytic activity that induced immunometabolic changes. Recombinant mutant LGp40, without enzyme activity, showed no protective effect against HDM-induced airway inflammation.

CONCLUSIONS

We found a novel mechanism of moonlighting LGp40 in the reversal of M2-prompted Th2 cell activation through glycolytic activity, which has an important immunoregulatory role in preventing allergic asthma. Our results provide a new strategy for probiotics application in alleviating allergic asthma.

Betaine Supplementation Causes an Increase in Fatty Acid Oxidation and Carbohydrate Metabolism in Livers of Mice Fed a High-Fat Diet: A Proteomic Analysis

Betaine, a common methyl donor whose methylation is involved in the biosynthesis of carnitine and phospholipids in animals, serves as food and animal feed additive. The present study used liquid chromatography-mass spectrometry (LC-MS) to analyze the liver protein profile of mice on a high fat (HF) diet to investigate the mechanism by which betaine affects hepatic metabolism. Although betaine supplementation had no significant effect on body weight, a total of 103 differentially expressed proteins were identified between HF diet + 1% betaine group (HFB) and HF diet group by LC-MS (fold change > 2, p < 0.05). The addition of 1% betaine had a significant enhancement of the expression of enzymes related to fatty acid oxidation metabolism, such as hydroxyacyl-Coenzyme A dehydrogenase (HADHA), enoyl Coenzyme A hydratase 1 (ECHS1) (p < 0.05) etc., and the expression of apolipoprotein A-II (APOA2) protein was significantly reduced (p < 0.01). Meanwhile, the protein expression of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and succinate-CoA ligase (SUCLG1) were highly significant (p < 0.01). Pathway enrichment using the Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed that the functions of differential proteins involved fatty acid catabolism, carbohydrate metabolism, tricarboxylic acid cycle (TCA) and peroxisome proliferator-activated receptor alpha (PPARα) signaling pathway. Protein−protein interaction (PPI) analysis discovered that acetyl-Coenzyme A acetyltransferase 1 (ACAT1), HADHA and ECHS1 were central hubs of hepatic proteomic changes in the HFB group of mice. Betaine alleviates hepatic lipid accumulation by enhancing fatty acid oxidation and accelerating the TCA cycle and glycolytic process in the liver of mice on an HF diet.

Discovery of Non-Cysteine-Targeting Covalent Inhibitors by Activity-Based Proteomic Screening with a Cysteine-Reactive Probe

Covalent inhibitors of enzymes are increasingly appreciated as pharmaceutical seeds, yet discovering non-cysteine-targeting inhibitors remains challenging. Herein, we report an intriguing experience during our activity-based proteomic screening of 1601 reactive small molecules, in which we monitored the ability of library molecules to compete with a cysteine-reactive iodoacetamide probe. One epoxide molecule, F8, exhibited unexpected enhancement of the probe reactivity for glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a rate-limiting glycolysis enzyme. In-depth mechanistic analysis suggests that F8 forms a covalent adduct with an aspartic acid in the active site to displace NAD⁺, a cofactor of the enzyme, with concomitant enhancement of the probe reaction with the catalytic cysteine. The mechanistic underpinning permitted the identification of an optimized aspartate-reactive GAPDH inhibitor. Our findings exemplify that activity-based proteomic screening with a cysteine-reactive probe can be used for discovering covalent inhibitors that react with non-cysteine residues.

Elevated glycolysis imparts functional ability to CD8+ T cells in HIV infection

The mechanisms inducing exhaustion of HIV-specific CD8⁺ T cells are not fully understood. Metabolic programming directly influences T-cell differentiation, effector function, and memory. We evaluated metabolic profiles of ex vivo CD8⁺ T cells in HIV-infected individuals. The baseline oxygen consumption rate of CD8⁺ T cells was elevated in all infected individuals and CD8⁺ T cells were working at maximal respiratory capacity. The baseline glycolysis rate was enhanced only during early untreated HIV and in viral controllers, but glycolytic capacity was conserved at all stages of infection. CD8⁺ T-cell mTOR activity was found to be reduced. Enhanced glycolysis was crucial for HIV-specific killing of CD8⁺ T cells. CD8⁺ T-cell cytoplasmic GAPDH content was reduced in HIV, but less in early infection and viral controllers. Thus, CD8⁺ T-cell exhaustion in HIV is characterized by reduced glycolytic activity, enhanced OXPHOS demands, dysregulated mTOR, and reduced cytoplasmic GAPDH. These data provide potential metabolic strategies to reverse CD8⁺ T-cell dysfunction in HIV.

Immunomodulatory effect of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in allergic conditions in vitro and in vivo

We found that strawberry extract suppressed immunoglobulin (Ig) E production in vitro and in vivo, and identified glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as one of the IgE suppressor in the extract. We report here the effect of GAPDH on various Ig productions in vitro and in vivo. GAPDH suppressed IgE and enhanced IgA, IgG and IgM productions in ovalbumin (OVA)-stimulated human peripheral blood mononuclear cells. Oral administration of GAPDH at 10 mg/kg/day to OVA-induced allergy model mice tended to decrease total IgE level and increase total IgA and IgG levels in sera, and also decreased OVA-specific IgE and IgG levels. It is known that the increase of total IgA as well as the decrease of total and specific IgE is important for alleviating allergic symptoms. In addition, GAPDH accelerated IgA production and increased some cytokine secretions such as IL-4, TGF-β1 and IFN-γ in the OVA-immunized mice spleen lymphocytes. These cytokines involved in the class-switching, IgA enhancement, and IgE suppression, respectively, supporting above results. Our study suggests a possibility that oral administration of GAPDH may induce the immunomodulation in allergic responses.

Moonlighting Proteins Are Important Players in Cancer Immunology

Plasticity and adaptation to environmental stress are the main features that tumor and immune system share. Except for intrinsic and high-defined properties, cancer and immune cells need to overcome the opponent's defenses by activating more effective signaling networks, based on common elements such as transcriptional factors, protein-based complexes and receptors. Interestingly, growing evidence point to an increasing number of proteins capable of performing diverse and unpredictable functions. These multifunctional proteins are defined as moonlighting proteins. During cancer progression, several moonlighting proteins are involved in promoting an immunosuppressive microenvironment by reprogramming immune cells to support tumor growth and metastatic spread. Conversely, other moonlighting proteins support tumor antigen presentation and lymphocytes activation, leading to several anti-cancer immunological responses. In this light, moonlighting proteins could be used as promising new potential targets for improving current cancer therapies. In this review, we describe in details 12 unprecedented moonlighting proteins that during cancer progression play a decisive role in guiding cancer-associated immunomodulation by shaping innate or adaptive immune response.

Partial catalytic Cys oxidation of human GAPDH to Cys-sulfonic acid

Background: n-Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyses the NAD ⁺-dependent oxidative phosphorylation of n-glyceraldehyde-3-phosphate to 1,3-diphospho-n-glycerate and its reverse reaction in glycolysis and gluconeogenesis.

Methods: Four distinct crystal structures of human n-Glyceraldehyde-3-phosphate dehydrogenase ( HsGAPDH) have been determined from protein purified from the supernatant of HEK293F human epithelial kidney cells.

Results: X-ray crystallography and mass-spectrometry indicate that the catalytic cysteine of the protein ( HsGAPDH Cys152) is partially oxidised to cysteine S-sulfonic acid. The average occupancy for the Cys152-S-sulfonic acid modification over the 20 crystallographically independent copies of HsGAPDH across three of the crystal forms obtained is 0.31±0.17.

Conclusions: The modification induces no significant structural changes on the tetrameric enzyme, and only makes aspecific contacts to surface residues in the active site, in keeping with the hypothesis that the oxidising conditions of the secreted mammalian cell expression system result in HsGAPDH catalytic cysteine S-sulfonic acid modification and irreversible inactivation of the enzyme.

Partial catalytic Cys oxidation of human GAPDH

Background: n-Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyses the reversible NAD+-dependent oxidative phosphorylation of n-glyceraldehyde-3-phosphate to 1,3-diphospho-n-glycerate in both glycolysis and gluconeogenesis.Methods: Four distinct crystal structures of human n-Glyceraldehyde-3-phosphate dehydrogenase (HsGAPDH) have been determined from protein purified from the supernatant of HEK293F human epithelial kidney cells.Results: X-ray crystallography and mass-spectrometry indicate that the catalytic cysteine of the protein (HsGAPDH Cys152) is partially oxidised to cysteine S-sulfonic acid. The average occupancy for the Cys152-S-sulfonic acid modification over the 20 crystallographically independent copies ofHsGAPDH across three of the crystal forms obtained is 0.31±0.17.Conclusions: The modification induces no significant structural changes on the tetrameric enzyme, and only makes aspecific contacts to surface residues in the active site, in keeping with the hypothesis that the oxidising conditions of the secreted mammalian cell expression system result inHsGAPDH catalytic cysteine S-sulfonic acid modification and irreversible inactivation of the enzyme.

pdh modulate virulence through reducing stress tolerance and biofilm formation of Streptococcus suis serotype 2

Streptococcus suis serotype 2 (S. suis 2) is a zoonotic pathogen. It causes meningitis, arthritis, pneumonia and sepsis in pigs, leading to extremely high mortality, which seriously affects public health and the development of the pig industry. Pyruvate dehydrogenase (PDH) is an important sugar metabolism enzyme that is widely present in microorganisms, mammals and higher plants. It catalyzes the irreversible oxidative decarboxylation of pyruvate to acetyl-CoA and reduces NAD+ to NADH. In this study, we found that the virulence of the S. suis ZY05719 sequence type 7 pdh deletion strain (Δpdh) was significantly lower than the wild-type strain (WT) in the mouse infection model. The distribution of viable bacteria in the blood and organs of mice infected with the Δpdh was significantly lower than those infected with WT. Bacterial survival rates were reduced in response to temperature stress, salt stress and oxidative stress. Additionally, compared to WT, the ability to adhere to and invade PK15 cells, biofilm formation and stress resistance of Δpdh were significantly reduced. Moreover, real-time PCR results showed that pdh deletion reduced the expression of multiple adhesion-related genes. However, there was no significant difference in the correlation biological analysis between the complemented strain (CΔpdh) and WT. Moreover, the survival rate of Δpdh in RAW264.7 macrophages was significantly lower than that of the WT strain. This study shows that PDH is involved in the pathogenesis of S. suis 2 and reduction in virulence of Δpdh may be related to the decreased ability to resist stress of the strain.

Metabolomic Profile of BALB/c Macrophages Infected with Leishmania amazonensis: Deciphering L-Arginine Metabolism

Background: Leishmaniases are neglected tropical diseases that are caused by Leishmania, being endemic worldwide. L-arginine is an essential amino acid that is required for polyamines production on mammal cells. During Leishmania infection of macrophages, L-arginine is used by host and parasite arginase to produce polyamines, leading to parasite survival; or, by nitric oxide synthase 2 to produce nitric oxide leading to parasite killing. Here, we determined the metabolomic profile of BALB/c macrophages that were infected with L. amazonensis wild type or with L. amazonensis arginase knockout, correlating the regulation of L-arginine metabolism from both host and parasite. Methods: The metabolites of infected macrophages were analyzed by capillary electrophoresis coupled with mass spectrometry (CE-MS). The metabolic fingerprints analysis provided the dual profile from the host and parasite. Results: We observed increased levels of proline, glutamic acid, glutamine, L-arginine, ornithine, and putrescine in infected-L. amazonensis wild type macrophages, which indicated that this infection induces the polyamine production. Despite this, we observed reduced levels of ornithine, proline, and trypanothione in infected-L. amazonensis arginase knockout macrophages, indicating that this infection reduces the polyamine production. Conclusions: The metabolome fingerprint indicated that Leishmania infection alters the L-arginine/polyamines/trypanothione metabolism inside the host cell and the parasite arginase impacts on L-arginine metabolism and polyamine production, defining the infection fate.

Early response of C2C12 myotubes to a sub-cytotoxic dose of hemorrhagic metalloproteinase HF3 from Bothrops jararaca venom

Manifestations of local tissue damage, such as hemorrhage and myonecrosis, are among the most dramatic effects of envenomation by viperid snakes. Snake venom metalloproteinases (SVMPs) of the P-III class are main players of the hemorrhagic effect due to their activities in promoting blood vessel disruption. Hemorrhagic Factor 3 (HF3), a P-III class SVMP from Bothrops jararaca, shows a minimum hemorrhagic dose of 240 fmol on rabbit skin. The aim of this study was to assess the effects of a sub-cytotoxic dose of HF3 (50 nM) on the proteomic profile of C2C12 differentiated cells (myotubes) in culture, and on the peptidomic profile of the culture supernatant. Quantitative proteomic analysis using stable-isotope dimethyl labeling showed differential abundance of various proteins including enzymes involved in oxidative stress and inflammation responses. Identification of peptides in the supernatant of HF3-treated myotubes revealed proteolysis and pointed out potential new substrates of HF3, including glyceraldehyde-3-phosphate dehydrogenase, and some damage-associated molecular patterns (DAMPs). These experiments demonstrate the subtle effects of HF3 on muscle cells and illustrate for the first time the early proteolytic events triggered by HF3 on myotubes. Moreover, they may contribute to future studies aimed at explaining the inflammation process, hemorrhage and myonecrosis caused by SVMPs. SIGNIFICANCE: One of the main features of viperid snake envenomation is myotoxicity at the bite site, which, in turn is often associated with edema, blistering and hemorrhage, composing a complex pattern of local tissue damage. In this scenario, besides muscle cells, other types of cells, components of the extracellular matrix and blood vessels may also be affected, resulting in an outcome of deficient muscle regeneration. The main venom components participating in this pathology are metalloproteinases and phospholipases A2. Muscle necrosis induced by metalloproteinases is considered as an indirect effect related to ischemia, due to hemorrhage resulted from damage to the microvasculature. The pathogenesis of local effects induced by Bothrops venoms or isolated toxins has been studied by traditional methodologies. More recently, proteomic and peptidomic approaches have been used to study venom-induced pathogenesis. Here, in order to investigate the role of metalloproteinase activity in local tissue damage, we asked whether the hemorrhagic metalloproteinase HF3, at sub-cytotoxic levels, could alter the proteome of C2C12 myotubes in culture, thereby providing an insight into the mechanisms for the development of myonecrosis. Our results from mass spectrometric analyses showed subtle, early changes in the cells, including differential abundance of some proteins and proteolysis in the culture supernatant. The data illustrate the potential ability of metalloproteinases to trigger early systemic responses progressing from local cells and up to tissues.

Tumour necrosis factor signalling in health and disease

The master pro-inflammatory cytokine, tumour necrosis factor (TNF), has been shown to modulate multiple signalling pathways, with wide-ranging downstream effects. TNF plays a vital role in the typical immune response through the regulation of a number of pathways encompassing an immediate inflammatory reaction with significant innate immune involvement as well as cellular activation with subsequent proliferation and programmed cell death or necrosis. As might be expected with such a broad spectrum of cellular effects and complex signalling pathways, TNF has also been implicated in a number of disease states, such as rheumatoid arthritis, ankylosing spondylitis, and Crohn’s disease. Since the time of its discovery over 40 years ago, TNF ligand and its receptors, TNF receptor (TNFR) 1 and 2, have been categorised into two complementary superfamilies, namely TNF (TNFSF) and TNFR (TNFRSF), and 19 ligands and 29 receptors have been identified to date. There have been significant advances in our understanding of TNF signalling pathways in the last decade, and this short review aims to elucidate some of the most recent advances involving TNF signalling in health and disease.

Maternal exposure to traffic pollutant causes impairment of spermatogenesis and alterations of genome-wide mRNA and microRNA expression in F2 male mice

Male spermatogenesis dysfunctions are associated with environmental pollutants, but the detailed mechanisms remain poorly understood. In this study, healthy C57BL/6 J mice were used to establish an animal model of maternal exposure to traffic pollutant during pregnancy, and the toxic effects on the reproductive system of F2 male mice were analysed using mRNA and miRNA microarray. Our results showed that 54 miRNAs and 1927 mRNAs were significantly altered in the exposed group. Gene Ontology (GO) analysis revealed that the most significant GO terms for biological process, molecular function and cellular component were myeloid cell differentiation, growth factor binding and main axon. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis demonstrated that the biosynthesis of amino acids was the most significant pathway and that the cytokine-cytokine receptor interaction was the most abundant pathway (37 genes). Protein-protein interaction (PPI) and the miRNA-mRNA network were constructed with Cytoscape. The hub genes, Tnf, Il10 and Gapdh, were closely related to immuno-regulation and their miRNA regulators were reversely changed. Together, our results indicate that maternal exposure to traffic pollutant can cause spermatogenesis damage in F2 male mice possibly through the destroyed immunoprivileged environment in testis mediated by the aberrant expression of miRNA and mRNA.