Cyclooxygenase 2 pathway and its therapeutic inhibition in superantigen-induced toxic shock

Blockade of Cycloxygenase-2 ameliorates sepsis induced immune-suppression by regulating myeloid-derived suppressor cells

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) and cyclooxy-genase-2 (COX-2)/Prostaglandin E2 (PGE2) axis are important contributors to sepsis-induced immune-suppression. The purpose of present study is to explore whether COX-2 inhibitor can improve immunological disorder after sepsis via regulating MDSCs.

METHODS

A ''two-hit'' model reflecting clinical sepsis development was performed. Cecal ligation and puncture (CLP) and Legionella pneumophila infection were used as the first and the second hit, respectively. NS398, a selective COX-2 inhibitor, was utilized to treat septic mice. The motality, bacterial counts in the lung, systematic inflammatory reaction and CD4 + T cells response after sepsis were assessed, so as the frequency and function of MDSCs. In some experiments, the number of MDSCs was manipulated by adoptive transfer or neutralizing antibody before induction of secondary infection.

RESULTS

Mice surviving CLP showed a marked expansion and activation of MDSCs in spleen, accompanied by suppressed proliferating capability, impaired secreting functionand increased apoptosis of CD4 + T cells. Majority of CLP survivors became succumbed to L. pneumophila invasion, associated with defective bacteria elimination ability. NS398 treatment was found to ameliorate these adverse outcomes significantly.

CONCLUSION

MDSCs contribute greatly to the sepsis-induced immune dysfunction. Inhibiting COX-2 may become a promising therapy that targets MDSCs-induced immunosuppression.

"Small" Intestinal Immunopathology Plays a "Big" Role in Lethal Cytokine Release Syndrome, and Its Modulation by Interferon-γ, IL-17A, and a Janus Kinase Inhibitor

Chimeric antigen receptor T cell (CART) therapy, administration of certain T cell-agonistic antibodies, immune check point inhibitors, coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome–coronavirus 2 (SARS-CoV-2) and Toxic shock syndrome (TSS) caused by streptococcal as well as staphylococcal superantigens share one common complication, that is T cell-driven cytokine release syndrome (CRS) accompanied by multiple organ dysfunction (MOD). It is not understood whether the failure of a particular organ contributes more significantly to the severity of CRS. Also not known is whether a specific cytokine or signaling pathway plays a more pathogenic role in precipitating MOD compared to others. As a result, there is no specific treatment available to date for CRS, and it is managed only symptomatically to support the deteriorating organ functions and maintain the blood pressure. Therefore, we used the superantigen-induced CRS model in HLA-DR3 transgenic mice, that closely mimics human CRS, to delineate the immunopathogenesis of CRS as well as to validate a novel treatment for CRS. Using this model, we demonstrate that (i) CRS is characterized by a rapid rise in systemic levels of several Th1/Th2/Th17/Th22 type cytokines within a few hours, followed by a quick decline. (ii) Even though multiple organs are affected, small intestinal immunopathology is the major contributor to mortality in CRS. (iii) IFN-γ deficiency significantly protected from lethal CRS by attenuating small bowel pathology, whereas IL-17A deficiency significantly increased mortality by augmenting small bowel pathology. (iv) RNA sequencing of small intestinal tissues indicated that IFN-γ-STAT1-driven inflammatory pathways combined with enhanced expression of pro-apoptotic molecules as well as extracellular matrix degradation contributed to small bowel pathology in CRS. These pathways were further enhanced by IL-17A deficiency and significantly down-regulated in mice lacking IFN-γ. (v) Ruxolitinib, a selective JAK-1/2 inhibitor, attenuated SAg-induced T cell activation, cytokine production, and small bowel pathology, thereby completely protecting from lethal CRS in both WT and IL-17A deficient HLA-DR3 mice. Overall, IFN-γ-JAK-STAT-driven pathways contribute to lethal small intestinal immunopathology in T cell-driven CRS.

The role of cyclooxygenase-2 in mechanical ventilation-induced lung injury

Mechanical ventilation is necessary for patients with acute respiratory failure, but can cause or propagate lung injury. We previously identified cyclooxygenase-2 as a candidate gene in mechanical ventilation-induced lung injury. Our objective was to determine the role of cyclooxygenase-2 in mechanical ventilation-induced lung injury and the effects of cyclooxygenase-2 inhibition on lung inflammation and barrier disruption. Mice were mechanically ventilated at low and high tidal volumes, in the presence or absence of pharmacologic cyclooxygenase-2-specific inhibition with 3-(4-methylsulphonylphenyl)-4-phenyl-5-trifluoromethylisoxazole (CAY10404). Lung injury was assessed using markers of alveolar-capillary leakage and lung inflammation. Cyclooxygenase-2 expression and activity were measured by Western blotting, real-time PCR, and lung/plasma prostanoid analysis, and tissue sections were analyzed for cyclooxygenase-2 staining by immunohistochemistry. High tidal volume ventilation induced lung injury, significantly increasing both lung leakage and lung inflammation relative to control and low tidal volume ventilation. High tidal volume mechanical ventilation significantly induced cyclooxygenase-2 expression and activity, both in the lungs and systemically, compared with control mice and low tidal volume mice. The immunohistochemical analysis of lung sections localized cyclooxygenase-2 expression to monocytes and macrophages in the alveoli. The pharmacologic inhibition of cyclooxygenase-2 with CAY10404 significantly decreased cyclooxygenase activity and attenuated lung injury in mice ventilated at high tidal volume, attenuating barrier disruption, tissue inflammation, and inflammatory cell signaling. This study demonstrates the induction of cyclooxygenase-2 by mechanical ventilation, and suggests that the therapeutic inhibition of cyclooxygenase-2 may attenuate ventilator-induced acute lung injury.

Human leukocyte antigen class II transgenic mouse model unmasks the significant extrahepatic pathology in toxic shock syndrome

Among the exotoxins produced by Staphylococcus aureus and Streptococcus pyogenes, the superantigens (SAgs) are the most potent T-cell activators known to date. SAgs are implicated in several serious diseases including toxic shock syndrome (TSS), Kawasaki disease, and sepsis. However, the immunopathogenesis of TSS and other diseases involving SAgs are still not completely understood. The commonly used conventional laboratory mouse strains do not respond robustly to SAgs in vivo. Therefore, they must be artificially rendered susceptible to TSS by using sensitizing agents such as d-galactosamine (d-galN), which skews the disease exclusively to the liver and, hence, is not representative of the disease in humans. SAg-induced TSS was characterized using transgenic mice expressing HLA class II molecules that are extremely susceptible to TSS without d-galN. HLA-DR3 transgenic mice recapitulated TSS in humans with extensive multiple-organ inflammation affecting the lung, liver, kidneys, heart, and small intestines. Heavy infiltration with T lymphocytes (both CD4(+) and CD8+), neutrophils, and macrophages was noted. In particular, the pathologic changes in the small intestines were extensive and accompanied by significantly altered absorptive functions of the enterocytes. In contrast to massive liver failure alone in the d-galN sensitization model of TSS, findings of the present study suggest that gut dysfunction might be a key pathogenic event that leads to high morbidity and mortality in humans with TSS.

Early gene expression changes induced by the bacterial superantigen staphylococcal enterotoxin B and its modulation by a proteasome inhibitor

Toxic shock syndrome (TSS) is an acute, serious systemic illness caused by bacterial superantigens. Nonavailability of a suitable animal model until recently has hampered an in-depth understanding of the pathogenesis of TSS. In the current study, we characterized the early molecular events underlying TSS using our HLA-DR3 transgenic mouse model. Gene expression profiling using DNA microarrays identified a rapid and significant upregulation of several pro- as well as anti-inflammatory mediators, many of which have never been previously described in TSS. In vivo administration of staphylococcal enterotoxin B (SEB) led to an increase in the expression of Th0- (IL-2, 240-fold); Th1- (IFN-gamma, 360-fold; IL-12, 8-fold); Th2- (IL-4, 53-fold; IL-5, 4-fold) as well as Th17-type cytokines (IL-21, 19-fold; IL-17, 5-fold). The immunoregulatory cytokines (IL-6, 700-fold; IL-10, 18-fold); CC chemokines (such as CCL 2, 11, 3, 24, 17, 12, 7), CXC chemokines (such as CXCL 1, 2, 5, 11, 10, 19); and several proteases (matrix metalloproteinases 13, 8, 3, and 9) were also upregulated. Serum levels of several of these cytokines/chemokines were also significantly elevated. Pathway analyses revealed significant modulation in a variety of biochemical and cellular functions, providing molecular insights into the pathogenesis of TSS. Administration of bortezomib, a clinically approved proteasome inhibitor capable of blocking NF-kappaB pathway, was able to significantly modulate the expression of a variety of genes induced by SEB. Thus, our study showed that TSS is a complex process and emphasized the potential of use of bortezomib in the therapy of superantigen-induced TSS.