Bacterial Dose-Dependent Role of G Protein-Coupled Receptor Kinase 5 in Escherichia coli-Induced Pneumonia. Infect Immun. 2016;84:1633-1641. [PMID: 26975990 DOI: 10.1128/iai.00051-16]

Porphyromonas gingivalis virulence factors induce toxic effects in SH-SY5Y neuroblastoma cells: GRK5 modulation as a protective strategy

Periodontitis (PDS) is a chronic inflammatory disease initiated by a dysbiosis of oral pathogenic bacterial species, such as Porphyromonas gingivalis (Pg). These bacteria can penetrate the bloodstream, releasing various endo and exotoxins that fuel the infection, and stimulate toxic inflammation in different compartments, including the brain. However, the specific mechanisms by which PDS/Pg contribute to brain disorders, such as Alzheimer's disease (AD), remain unclear. This study assessed the effects of Pg's virulence factors - lipopolysaccharide (LPS-Pg) and gingipains (gps) K (Kgp) and Rgp - on SH-SY5Y cells. Our results demonstrated that LPS-Pg activated signaling through the Toll-like receptor (TLR)-2/4 induced a significant downregulation of G protein-coupled receptor kinase 5 (GRK5). Additionally, LPS-Pg stimulation resulted in a robust increase in Tau phosphorylation (pTau) and p53 levels, while causing a marked reduction in Bcl2 and increased cell death compared to unstimulated cells (Ns). LPS-Pg also elevated inducible nitric oxide synthase (iNOS) expression, leading to oxidative damage. In cells overexpressing GRK5 via Adenovirus, LPS-Pg failed to increase iNOS and pTau levels compared to GFP control cells. High GRK5 levels also prevented the nuclear accumulation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB). Furthermore, the overexpression of a GRK5 mutant form lacking the nuclear localization signal (ΔNLS) nearly abolished LPS-Pg induced p53 and iNOS upregulation. Finally, we tested whether Kgp and Rgp mediated similar effects and our data showed that both gps caused a marked downregulation of GRK5 leading to increased p53 and pTau levels. In conclusion, this study provides further insight into the toxic effects elicited by Pg in cells and suggests that preventing GRK5 deficiency may be a valid strategy to mitigate Pg-induced toxic effects (i.e. cell death, oxidative damage, and Tau hyperphosphorylation) in SH-SY5Y cells, which are typical molecular hallmarks of neurodegenerative disorders.

Construction of a potentially functional lncRNA-miRNA-mRNA network in sepsis by bioinformatics analysis

Objective: Sepsis is a common disease in internal medicine, with a high incidence and dangerous condition. Due to the limited understanding of its pathogenesis, the prognosis is poor. The goal of this project is to screen potential biomarkers for the diagnosis of sepsis and to identify competitive endogenous RNA (ceRNA) networks associated with sepsis.

Methods: The expression profiles of long non-coding RNAs (lncRNAs), microRNAs (miRNAs) and messenger RNAs (mRNAs) were derived from the Gene Expression Omnibus (GEO) dataset. The differentially expressed lncRNAs (DElncRNAs), miRNAs (DEmiRNAs) and mRNAs (DEmRNAs) were screened by bioinformatics analysis. DEmRNAs were analyzed by protein-protein interaction (PPI) network analysis, transcription factor enrichment analysis, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and Gene Set Enrichment Analysis (GSEA). After the prediction of the relevant database, the competitive ceRNA network is built in Cytoscape. The gene-drug interaction was predicted by DGIgb. Finally, quantitative real-time polymerase chain reaction (qRT-PCR) was used to confirm five lncRNAs from the ceRNA network.

Results: Through Venn diagram analysis, we found that 57 DElncRNAs, 6 DEmiRNAs and 317 DEmRNAs expressed abnormally in patients with sepsis. GO analysis and KEGG pathway analysis showed that 789 GO terms and 36 KEGG pathways were enriched. Through intersection analysis and data mining, 5 key KEGG pathways and related core genes were revealed by GSEA. The PPI network consists of 247 nodes and 1,163 edges, and 50 hub genes are screened by the MCODE plug-in. In addition, there are 5 DElncRNAs, 6 DEmiRNAs and 28 DEmRNAs in the ceRNA network. Drug action analysis showed that 7 genes were predicted to be molecular targets of drugs. Five lncRNAs in ceRNA network are verified by qRT-PCR, and the results showed that the relative expression of five lncRNAs was significantly different between sepsis patients and healthy control subjects.

Conclusion: A sepsis-specific ceRNA network has been effectively created, which is helpful to understand the interaction between lncRNAs, miRNAs and mRNAs. We discovered prospective sepsis peripheral blood indicators and proposed potential treatment medicines, providing new insights into the progression and development of sepsis.

Poly(I:C) Priming Exacerbates Cecal Ligation and Puncture-Induced Polymicrobial Sepsis in Mice

Sepsis continues to be a major healthcare issue with one of the highest mortality rates in intensive care units. Toll-like receptors are pattern recognition receptors that are intricately involved in the pathogenesis of sepsis. TLR3 is a major receptor for double-stranded RNA and is largely associated with immunity to viral infection. In this study, we examined the role of TLR3 priming in the immunopathology of sepsis using cecal-ligation and puncture (CLP) model of sepsis in mice. Mice injected with vehicle or poly(I:C) were subjected to sham or CLP surgery and various parameters of sepsis, including mortality, inflammation, and bacterial clearance were assessed. Poly(I:C) pre-treatment significantly enhanced mortality in mice subjected to CLP. Consistent with this, inflammatory cytokines including TNFα, IL-12p40, IFNγ, and MCP-1 were enhanced both systemically and locally in the poly(I:C)-treated group compared to the vehicle control. In addition, bacterial load was significantly higher in the poly(I:C)-treated septic mice. These changes were associated with reduced macrophage activation (but not neutrophils) in the peritoneal cavity of poly(I:C) pre-treated mice compared to vehicle pre-treatment. Together our results demonstrate that poly(I:C) priming in sepsis is likely to be detrimental to the host due to effects on systemic inflammatory cytokines and bacterial clearance.

Role of G protein-coupled receptor kinase-6 in Escherichia coli lung infection model in mice

G protein-coupled receptor kinase-6 (GRK6) is a serine/threonine kinase that is important in inflammatory processes. In this study, we examined the role of GRK6 in Escherichia coli-induced lung infection and inflammation using GRK6 knockout (KO) and wild-type (WT) mice. Intratracheal instillation of E. coli significantly enhanced bacterial load in the bronchoalveolar lavage (BAL) of KO compared with WT mice. Reduced bacterial clearance in the KO mice was not due to an intrinsic defect in neutrophil phagocytosis or killing but as a result of reduced neutrophil numbers in the KO BAL. Interestingly, neutrophil numbers in the lung were increased in the KO compared with WT mice, suggesting a potential dysfunction in transepithelial migration of neutrophils from the lungs to the bronchoalveolar space. This effect was selective for lung tissue because peritoneal neutrophil numbers were similar between the two genotypes following peritoneal infection. Although neutrophil expression of CXCR2/CXCR3 was similar between WT and KO, IL-17A expression was higher in the KO compared with WT mice. These results suggest that enhanced neutrophil count in the KO lungs but reduced numbers in BAL are likely due to transepithelial migration defect and/or altered chemokines/cytokines. Together, our studies suggest a previously unrecognized and novel role for GRK6 in neutrophil migration specific to pulmonary tissue during bacterial infection.

G Protein-Coupled Receptor Kinases in the Inflammatory Response and Signaling

G protein-coupled receptor kinases (GRKs) are serine/threonine kinases that regulate a large and diverse class of G protein-coupled receptors (GPCRs). Through GRK phosphorylation and β-arrestin recruitment, GPCRs are desensitized and their signal terminated. Recent work on these kinases has expanded their role from canonical GPCR regulation to include noncanonical regulation of non-GPCR and nonreceptor substrates through phosphorylation as well as via scaffolding functions. Owing to these and other regulatory roles, GRKs have been shown to play a critical role in the outcome of a variety of physiological and pathophysiological processes including chemotaxis, signaling, migration, inflammatory gene expression, etc. This diverse set of functions for these proteins makes them popular targets for therapeutics. Role for these kinases in inflammation and inflammatory disease is an evolving area of research currently pursued in many laboratories. In this review, we describe the current state of knowledge on various GRKs pertaining to their role in inflammation and inflammatory diseases.

Oxidative stress-induced mitochondrial dysfunction in a normal colon epithelial cell line

AIM

To determine how a normal human colon cell line reacts to microbial challenge as a way to study oxidative stress-induced responses associated with inflammatory bowel disease.

METHODS

Normal human colon epithelial cells (ATCC^® CRL.1790™) were stimulated with either heat killed E. coli or heat killed murine cecal contents (HKC) and examined for several relevant biomarkers associated with inflammation and oxidative stress including cytokine production, mitochondrial autophagy and oxidant status. TNFα, IL-1β and IL-8 protein concentrations were measured within the supernatants. Fluorescent microscopy was performed to quantify the production of reactive oxygen species (ROS) using an oxidation responsive fluorogenic probe. Mitochondrial morphology and mitochondrial membrane potential was assessed by dual staining using COXIV antibody and a dye concentrating in active mitochondria. Mitochondrial ROS scavenger was used to determine the source of ROS in stimulated cells. Autophagy was detected by staining for the presence of autophagic vesicles. Positive controls for autophagy and ROS/RNS experiments were treated with rapamycin and chloroquine. Mitochondrial morphology, ROS production and autophagy microscopy experiments were analyzed using a custom acquisition and analysis microscopy software (ImageJ).

RESULTS

Exposing CRL.1790 cells to microbial challenge stimulated cells to produce several relevant biomarkers associated with inflammation and oxidative stress. Heat killed cecal contents treatment induced a 10-12 fold increase in IL-8 production by CRL.1790 cells compared to unstimulated controls at 6 and 12 h (P < 0.001). Heat killed E. coli stimulation resulted in a 4-5 fold increase in IL-8 compared to the unstimulated control cells at each time point (P < 0.001). Both heat killed E. coli and HKC stimulated robust ROS production at 6 (P < 0.001), and 12 h (P < 0.01). Mitochondrial morphologic abnormalities were detected at 6 and 12 h based on reduced mitochondrial circularity and decreased mitochondrial membrane potential, P < 0.01. Microbial stimulation also induced significant autophagy at 6 and 12 h, P < 0.01. Lastly, blocking mitochondrial ROS generation using mitochondrial specific ROS scavenger reversed microbial challenge induced mitochondrial morphologic abnormalities and autophagy.

CONCLUSION

The findings from this study suggest that CRL.1790 cells may be a useful alternative to other colon cancer cell lines in studying the mechanisms of oxidative stress events associated with intestinal inflammatory disorders.

Genetic risk factors for serious infections in inflammatory bowel diseases

INTRODUCTION

Immunosuppression, the cornerstone of management of Crohn's disease (CD) and ulcerative colitis (UC) (inflammatory bowel diseases; IBD) is associated with an increased risk of serious infections that is inadequately predicted by clinical risk factors. The role of genetics in determining susceptibility to infections is unknown.

METHODS

From a prospective-consented patient registry, we identified IBD patients with serious infections requiring hospitalization. Analysis was performed to identify IBD-related and non-IBD related immune response loci on the Immunochip that were associated with serious infections and a genetic risk score (GRS) representing the cumulative burden of the identified single nucleotide polymorphisms was calculated. Multivariable logistic regression used to identify effect of clinical and genetic factors.

RESULTS

The study included 1333 IBD patients (795 CD, 538 UC) with median disease duration of 13 years. A total of 133 patients (10%) had a serious infection requiring hospitalization. Patients with infections were more likely to have CD and had shorter disease duration. The most common infections were skin and soft-tissue, respiratory and urinary tract infections. Eight IBD risk loci and two other polymorphisms were significantly associations with serious infections. Each one point increase in the infection GRS was associated with a 50% increase in risk of infections (OR = 1.53, 95% CI = 1.37-1.70) (p = 1 × 10^-14), confirmed on multivariable analysis. Genetic risk factors improved performance of a model predicting infections over clinical covariates alone (p < 0.001).

CONCLUSIONS

Genetic risk factors may predict susceptibility to infections in patients with IBD.