Divergent results induced by different types of septic shock in transglutaminase 2 knockout mice

Screening of novel disease genes of sepsis-induced myocardial Disfunction by RNA sequencing and bioinformatics analysis

BACKGROUND

There is still a lack of effective treatment for sepsis-induced myocardial dysfunction (SIMD), while the pathogenesis of SIMD still remains largely unexplained.

METHODS

RNA sequencing results (GSE267388 and GSE79962) were used for cross-species integrative analysis. Bioinformatic analyses were used to delve into function, tissue- and cell- specificity, and interactions of genes. External datasets and qRT-PCR experiments were used for validation. L1000 FWD was used to predict targeted drugs, and 3D structure files were used for molecular docking.

RESULTS

Based on bioinformatic analyses, ten differentially expressed genes were selected as genes of interest, seven of which were verified to be significantly differential expression. Bucladesine was considered as a potential targeted drug for SIMD, which banded to seven target proteins primarily by forming hydrogen bonds.

CONCLUSION

It was considered that Cebpd, Timp1, Pnp, Osmr, Tgm2, Cp, and Asb2 were novel disease genes, while bucladesine was a potential therapeutic drug, of SIMD.

Increased Osteoclastogenesis in Absence of TG2 Is Reversed by Transglutaminase Inhibition-Evidence for the Role for TG1 in Osteoclast Formation

Osteoclasts are multinucleated, bone-resorbing giant cells derived from monocyte-macrophage cell lines. Increased bone resorption results in loss of bone mass and osteoporosis. Osteoclast and bone marrow macrophages have been shown to express three TG enzymes (TG2, Factor XIII-A, and TG1) and TG activity to regulate osteoclast differentiation from bone marrow macrophages in vitro. In vivo and in vitro studies have demonstrated that the deletion of TG2 causes increased osteoclastogenesis and a significant loss of bone mass in mice (Tgm2-/- mice). Here, we confirm that TG2 deficiency results in increased osteoclastogenesis in vitro and show that this increase can be reversed by a TG inhibitor, NC9, suggesting that other TGs are responsible for driving osteoclastogenesis in the absence of TG2. An assessment of total TG activity with 5-(biotinamido)-pentylamine, as well as TG1 and FXIII-A activities using TG-specific Hitomi peptides (bK5 and bF11) in Tgm2-/- bone marrow flushes, bone marrow macrophages, and osteoclasts, showed a significant increase in total TG activity and TG1 activity. Factor XIII-A activity was unchanged. Aspartate proteases, such as cathepsins, are involved in the degradation of organic bone matrix and can be produced by osteoclasts. Moreover, Cathepsin D was shown in previous work to be increased in TG2-null cells and is known to activate TG1. We show that Pepstatin A, an aspartate protease inhibitor, blocks osteoclastogenesis in wild-type and Tgm2-/- cells and decreases TG1 activity in Tgm2-/- osteoclasts. Cathepsin D protein levels were unaltered in Tgm2-/-cells and its activity moderately but significantly increased. Tgm2-/- and Tgm2+/+ bone marrow macrophages and osteoclasts also expressed Cathepsin E, and Renin of the aspartate protease family, suggesting their potential involvement in this process. Our study brings further support to the observation that TGs are significant regulators of osteoclastogenesis and that the absence of TG2 can cause increased activity of other TGs, such as TG1.

Establishment and validation of a logistic regression model for prediction of septic shock severity in children

Background

Septic shock is the most severe complication of sepsis, and is a major cause of childhood mortality, constituting a heavy public health burden.

Methods

We analyzed the gene expression profiles of septic shock and control samples from the Gene Expression Omnibus (GEO). Four differentially expressed genes (DEGs) from survivor and control groups, non-survivor and control groups, and survivor and non-survivor groups were selected. We used data about these genes to establish a logistic regression model for predicting the survival of septic shock patients.

Results

Leave-one-out cross validation and receiver operating characteristic (ROC) analysis indicated that this model had good accuracy. Differential expression and Gene Set Enrichment Analysis (GSEA) between septic shock patients stratified by prediction score indicated that the systemic lupus erythematosus pathway was activated, while the limonene and pinene degradation pathways were inactivated in the high score group.

Conclusions

Our study provides a novel approach for the prediction of the severity of pathology in septic shock patients, which are significant for personalized treatment as well as prognostic assessment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-021-00206-9.

Transglutaminase 2 as a Marker for Inflammation and Therapeutic Target in Sepsis

Sepsis results in lethal organ malfunction due to dysregulated host response to infection, which is a condition with increasing prevalence worldwide. Transglutaminase 2 (TG2) is a crosslinking enzyme that forms a covalent bond between lysine and glutamine. TG2 plays important roles in diverse cellular processes, including extracellular matrix stabilization, cytoskeletal function, cell motility, adhesion, signal transduction, apoptosis, and cell survival. We have shown that the co-culture of Candida albicans and hepatocytes activates and induces the translocation of TG2 into the nucleus. In addition, the expression and activation of TG2 in liver macrophages was dramatically induced in the lipopolysaccharide-injected and cecal ligation puncture-operated mouse models of sepsis. Based on these findings and recently published research, we have reviewed the current understanding of the relationship between TG2 and sepsis. Following the genetic and pharmacological inhibition of TG2, we also assessed the evidence regarding the use of TG2 as a potential marker and therapeutic target in inflammation and sepsis.

A Precision Strategy to Cure Renal Cell Carcinoma by Targeting Transglutaminase 2

In a recent report, no significance of transglutaminase 2 (TGase 2) was noted in the analyses of expression differences between normal and clear cell renal cell carcinoma (ccRCC), although we found that knock down of TGase 2 induced significant p53-mediated cell death in ccRCC. Generally, to find effective therapeutic targets, we need to identify targets that belong specifically to a cancer phenotype that can be differentiated from a normal phenotype. Here, we offer precise reasons why TGase 2 may be the first therapeutic target for ccRCC, according to several lines of evidence. TGase 2 is negatively regulated by von Hippel-Lindau tumor suppressor protein (pVHL) and positively regulated by hypoxia-inducible factor 1-α (HIF-1α) in renal cell carcinoma (RCC). Therefore, most of ccRCC presents high level expression of TGase 2 because over 90% of ccRCC showed VHL inactivity through mutation and methylation. Cell death, angiogenesis and drug resistance were specifically regulated by TGase 2 through p53 depletion in ccRCC because over 90% of ccRCC express wild type p53, which is a cell death inducer as well as a HIF-1α suppressor. Although there have been no detailed studies of the physiological role of TGase 2 in multi-omics analyses of ccRCC, a life-long study of the physiological roles of TGase 2 led to the discovery of the first target as well as the first therapeutic treatment for ccRCC in the clinical field.

Imaging of the ex vivo transglutaminase activity in liver macrophages of sepsis mice

Sepsis is the leading cause of death in hospitalized patients and is characterized by a dysregulated inflammatory response to infection and multiple organ failure, including the liver. Transglutaminase 2 (TG2) is a multifunctional enzyme that exhibits transamidase, GTPase, and integrin-binding activities and has opposing roles in the regulation of cell growth, differentiation, and apoptosis. TG2 plays both pathogenic and protective roles in liver diseases, revealing the need to examine the activities of TG2. Here, we introduced an ex vivo imaging approach to examine the in vivo transamidase activity of TG2 based on the combination of intraperitoneal injection of 5-biotinamidopentylamine (5BAPA), a biotinylated substrate for TG2, and fluorescent streptavidin staining in frozen liver sections. Increased 5BAPA signals was observed in the livers of lipopolysaccharide (LPS) and cecal ligation and puncture (CLP)-induced sepsis mice. Pharmacological inhibition of TG2 activity ameliorated LPS-induced liver injury. 5BAPA signals were observed in TG2-expressing and F4/80-positive midzonal macrophages, providing direct evidence that activated macrophages are the major cellular source of active TG2 in the livers of sepsis mice. Further studies focusing on the activation of 5BAPA-stained midzonal macrophages may improve understanding of the molecular pathophysiology and the development of therapeutic strategies for sepsis.

Transglutaminases in Monocytes and Macrophages

Macrophages are key players in various inflammatory disorders and pathological conditions via phagocytosis and orchestrating immune responses. They are highly heterogeneous in terms of their phenotypes and functions by adaptation to different organs and tissue environments. Upon damage or infection, monocytes are rapidly recruited to tissues and differentiate into macrophages. Transglutaminases (TGs) are a family of structurally and functionally related enzymes with Ca²⁺-dependent transamidation and deamidation activity. Numerous studies have shown that TGs, particularly TG2 and Factor XIII-A, are extensively involved in monocyte- and macrophage-mediated physiological and pathological processes. In the present review, we outline the current knowledge of the role of TGs in the adhesion and extravasation of monocytes, the expression of TGs during macrophage differentiation, and the regulation of TG2 expression by various pro- and anti-inflammatory mediators in macrophages. Furthermore, we summarize the role of TGs in macrophage phagocytosis and the understanding of the mechanisms involved. Finally, we review the roles of TGs in tissue-specific macrophages, including monocytes/macrophages in vasculature, alveolar and interstitial macrophages in lung, microglia and infiltrated monocytes/macrophages in central nervous system, and osteoclasts in bone. Based on the studies in this review, we conclude that monocyte- and macrophage-derived TGs are involved in inflammatory processes in these organs. However, more in vivo studies and clinical studies during different stages of these processes are required to determine the accurate roles of TGs, their substrates, and the mechanisms-of-action.

Transglutaminases in autoimmune and inherited skin diseases: The phenomena of epitope spreading and functional compensation

Transglutaminases (TGs) are structurally and functionally related enzymes that modify the post-translational structure and activity of proteins or peptides, and thus are able to turn on or switch off their function. Depending on location and activities, TGs are able to modify the signalling, the function and the fate of cells and extracellular connective tissues. Besides mouse models, human diseases enable us to appreciate the function of various TGs. In this study, skin diseases induced by genetic damages or autoimmune targeting of these enzymes will be discussed. TG1, TG3 and TG5 contribute to the cutaneous barrier and thus to the integrity and function of epidermis. TGM1 mutations related to autosomal recessive ichthyosis subtypes, TGM5 mutations to a mild epidermolysis bullosa phenotype and as novelty TGM3 mutation to uncombable hair syndrome will be discussed. Autoimmunity to TG2, TG3 and TG6 may develop in a few of those genetically determined individuals who lost tolerance to gluten, and manifest as coeliac disease, dermatitis herpetiformis or gluten-dependent neurological symptoms, respectively. These gluten responder diseases commonly occur in combination. In autoimmune diseases, the epitope spreading is remarkable, while in some inherited pathologies, a unique compensation of the lost enzyme function is noted.

Transglutaminase 2 is dispensable but required for the survival of mice in dextran sulfate sodium-induced colitis

Transglutaminase 2 (TG2) is a ubiquitously expressed enzyme that catalyzes crosslinking, polyamination or deamidation of glutamine residues in proteins. It has been reported that TG2 is involved in the pathogenesis of various inflammatory diseases including celiac disease, pulmonary fibrosis, cystic fibrosis, multiple sclerosis and sepsis. Recently, using a mouse model of bleomycin-induced lung fibrosis, we showed that TG2 is required to trigger inflammation via the induction of T helper type 17 (Th17) cell differentiation in response to tissue damage. However, the role of TG2 in inflammatory bowel disease (IBD), which is thought to be a Th17 cell-associated disease, has remained elusive. In this study, we investigated the role of TG2 in dextran sulfate sodium (DSS)-induced colitis, the most widely used mouse model for IBD. Age- and sex-matched wild-type and TG2^-/- mice were fed 2% DSS for 7 days or 3.5% DSS for 5 days in drinking water. An in situ TG activity assay revealed that DSS treatment activates TG2 in various colon cell types, including columnar absorptive cells and goblet cells. DSS-treated TG2^-/- mice showed lower interleukin (IL)-6, but higher IL-17A and RORγt (retinoic acid receptor-related orphan receptor-γt) expression levels in the colon tissues than that in the wild-type mice. Moreover, TG2^-/- mice showed higher mortality than the wild-type mice because of DSS treatment. Nevertheless, we found no significant differences in changes of body weight, colon length, morphology, immune cell infiltration and in vivo intestinal permeability between DSS-treated wild-type and TG2^-/- mice. These results indicate that TG2-mediated Th17 cell differentiation is not required for the pathogenesis of DSS-induced acute colitis.

Is monocyte- and macrophage-derived tissue transglutaminase involved in inflammatory processes?

Monocytes and macrophages are key players in inflammatory processes following an infection or tissue damage. Monocytes adhere and extravasate into the inflamed tissue, differentiate into macrophages, and produce inflammatory mediators to combat the pathogens. In addition, they take up dead cells and debris and, therefore, take part in the resolution of inflammation. The multifunctional enzyme tissue Transglutaminase (TG2, tTG) is known to participate in most of those monocyte- and macrophage-mediated processes. Moreover, TG2 expression and activity can be regulated by inflammatory mediators. In the present review, we selectively elaborate on the expression, regulation, and contribution of TG2 derived from monocytes and macrophages to inflammatory processes mediated by those cells. In addition, we discuss the role of TG2 in certain pathological conditions, in which inflammation and monocytes and/or macrophages are prominently present, including atherosclerosis, sepsis, and multiple sclerosis. Based on the studies and considerations reported in this review, we conclude that monocyte- and macrophage-derived TG2 is clearly involved in various processes contributing to inflammation. However, TG2’s potential as a therapeutic target to counteract the possible detrimental effects or stimulate the potential beneficial effects on monocyte and macrophage responses during inflammation should be carefully considered. Alternatively, as TG2-related parameters can be used as a marker of disease, e.g., in celiac disease, or of disease-stage, e.g., in cancer, we put forward that this could be subject of research for monocyte- or macrophage-derived TG2 in inflammatory diseases.

Biomarker-based classification of bacterial and fungal whole-blood infections in a genome-wide expression study

Sepsis is a clinical syndrome that can be caused by bacteria or fungi. Early knowledge on the nature of the causative agent is a prerequisite for targeted anti-microbial therapy. Besides currently used detection methods like blood culture and PCR-based assays, the analysis of the transcriptional response of the host to infecting organisms holds great promise. In this study, we aim to examine the transcriptional footprint of infections caused by the bacterial pathogens Staphylococcus aureus and Escherichia coli and the fungal pathogens Candida albicans and Aspergillus fumigatus in a human whole-blood model. Moreover, we use the expression information to build a random forest classifier to classify if a sample contains a bacterial, fungal, or mock-infection. After normalizing the transcription intensities using stably expressed reference genes, we filtered the gene set for biomarkers of bacterial or fungal blood infections. This selection is based on differential expression and an additional gene relevance measure. In this way, we identified 38 biomarker genes, including IL6, SOCS3, and IRG1 which were already associated to sepsis by other studies. Using these genes, we trained the classifier and assessed its performance. It yielded a 96% accuracy (sensitivities >93%, specificities >97%) for a 10-fold stratified cross-validation and a 92% accuracy (sensitivities and specificities >83%) for an additional test dataset comprising Cryptococcus neoformans infections. Furthermore, the classifier is robust to Gaussian noise, indicating correct class predictions on datasets of new species. In conclusion, this genome-wide approach demonstrates an effective feature selection process in combination with the construction of a well-performing classification model. Further analyses of genes with pathogen-dependent expression patterns can provide insights into the systemic host responses, which may lead to new anti-microbial therapeutic advances.

Transglutaminse 2 and EGGL, the protein cross-link formed by transglutaminse 2, as therapeutic targets for disabilities of old age

Aging of the extracellular matrix (ECM), the protein matrix that surrounds and penetrates the tissues and binds the body together, contributes significantly to functional aging of tissues. ECM proteins become increasingly cross-linked with age, and this cross-linking is probably important in the decline of the ECM's function. This article reviews the role of ε-(γ-glutamyl)-lysine (EGGL), a cross-link formed by transglutaminase enzymes, and particularly the widely expressed isozyme transglutaminase 2 (TG2), in the aging ECM. There is little direct data on EGGL accumulation with age, and no direct evidence of a role of EGGL in the aging of the ECM with pathology. However, several lines of circumstantial evidence suggest that EGGL accumulates with age, and its association with pathology suggests that this might reflect degradation of ECM function. TG activity increases with age in many circumstances. ECM protein turnover is such that some EGGL made by TG is likely to remain in place for years, if not decades, in healthy tissue, and both EGGL and TG levels are enhanced by age-related diseases. If further research shows EGGL does accumulate with age, removing it could be of therapeutic benefit. Also reviewed is the blockade of TG and active removal of EGGL as therapeutic strategies, with the conclusion that both have promise. EGGL removal may have benefit for acute fibrotic diseases, such as tendinopathy, and for treating generalized decline in ECM function with old age. Extracellular TG2 and EGGL are therefore therapeutic targets both for specific and more generalized diseases of aging.

Anti-cancer effect of a quinoxaline derivative GK13 as a transglutaminase 2 inhibitor

PURPOSE

Transglutaminase 2 (TGase 2), a cross-linking enzyme, plays an important role in both pro-survival and anti-apoptosis during oncogenesis. For instance, TGase 2 induces NF-κB activation through I-κBα polymerization, which leads to the increase of pro-survival factors such as BCl-2. TGase 2 also suppresses apoptosis via depletion of caspase 3 and cathepsin D. Therefore, a specific TGase 2 inhibitor may become a very useful treatment for cancer showing high levels of TGase 2 expression.

METHODS

By small-molecule library screening, we managed to locate a competitive TGase 2 inhibiting quinoxaline compound (GK13) from 50 other quinoxaline derivatives. The 50 compounds that were screened represent a thousand structurally diverse, potentially pharmaceutical heterocyclic compound libraries, including benzopyrans, oxadiazoles, thiadiazoles, and quinoxalines. By measuring GI50, TGI, and LC50 using SRB assay, GK13 was selected.

RESULTS

In vitro enzyme kinetics using guinea pig liver TGase 2 showed that IC50 value was about 16.4 E-6 M. GK13 inhibits TGase 2-mediated I-κBα polymerization in a dose-dependent manner. LC50 of GK13 showed greater efficacy as 4.3E-4 M than LC50 of doxorubicin that showed efficacy as 3.87E-3 M in NCC72 composing 11 tissue origins and 72 cancer cell lines.

CONCLUSION

GK13 showed a possibility that quinoxaline derivatives may be effective for anti-cancer activity via TGase 2 inhibition.