BALB/c and C57BL/6 mice differ in oxidant and antioxidant responses in innate and adaptive immune cells in an asthma model induced by cockroach allergens.

Asthma is a complex and heterogenous disease affected by a multitude of factors. Several phenotypes of asthma exist which are influenced by various molecular mechanisms that include presence of antioxidant and oxidant enzymes in different immune cells such as dendritic cells (DCs), alveolar macrophages (AMs), neutrophils, and T cells. Close interaction between epithelial cells and dendritic cells initiates complex pathogenesis of asthma followed by involvement of other innate and adaptive immune cells. In chronic phase of the disease, these immune cells support each other in amplification of airway inflammation where oxidant-antioxidant balance is known to be an important contributing factor. Genetic variability in antioxidant response may influence the development of airway inflammation, however it has not been studied in mice yet. The two most studied mice strains, i.e. BALB/c and C57BL/6 are reported to have dissimilar airway responses to the same allergens due to their genetic makeup. In this investigation, we explored whether these strains had any differences in pulmonary oxidant-antioxidant system (Nrf2, SOD2, iNOS, HO-1, nitrotyrosine) in different immune cells (DCs, AMs, neutrophils, T cells), airway inflammation (presence of eosinophils and/or neutrophils) and mucus production in response to repeated cockroach allergen extract (CE) mouse model of asthma. Our data show that C57BL/6 mice had better induction of antioxidant system than BALB/c mice. Consequently, iNOS/nitrotyrosine levels were much exaggerated in BALB/c than C57BL/6 mice. As a result, BALB/c mice developed mixed granulocytic airway inflammation, whereas C57BL/6 developed mostly eosinophilic airway inflammation. Our data suggest that an exaggerated oxidant generation along with a weak antioxidant induction in response to a natural allergen on a susceptible genetic background may determine development of severe asthma phenotype such as mixed granulocyte inflammation.

Role of ITK signaling in acute kidney injury in mice: Amelioration of acute kidney injury associated clinical parameters and attenuation of inflammatory transcription factor signaling in CD4+ T cells by ITK inhibition.

Acute kidney injury (AKI) is a world-wide health problem and linked with increased risk of morbidity/mortality in hospitalized patients and its incidence has been on the rise in the last few decades. AKI is characterized by renal tubular injury which results from interactions between bacterial products and host immune responses which manifests as a rapid deterioration in renal function. Immune system dysfunction induced by sepsis plays a crucial role in AKI through activation of multiple immune cells of both innate and adaptive origin. These cells release pro-inflammatory cytokines such as IL-6, IL-17A, IFN-γ, and reactive oxygen metabolites. Adaptive immune cells, especially T cells also participate in the amplification of renal inflammation through release of pro-inflammatory cytokines such as IL-17A, IFN-γ, TNF-α, and IL-10. Non-receptor protein tyrosine kinases such as ITK play crucial role in T cell through modulation of key downstream molecules such as PLCγ, STAT3, NFkB, NFATc1, and p-38MAPK. However, it has not been explored in CD4+ T cells during AKI. Therefore, this study investigated the effect of ITK inhibitor on AKI linked clinical parameters (serum BUN, creatinine and renal histopathology), downstream signaling molecules in CD4+ T cells (PLCγ, STAT3, NFkB, and NFATc1), Th1/Th2/Treg cell markers (IL-17A, TNF-α, and IL-10), and neutrophil-mediated oxidative inflammation (MPO/carbonyl/nitrotyrosine formation) in mice. Our data exhibit elevated p-ITK levels in CD4+ T cells which is associated with renal dysfunction and elevated Th1/Th17/neutrophilic responses. Blockade of ITK signaling resulted in ameliorated of AKI associated biochemical; parameters through downregulation in transcription signaling in CD4+ T cells and Th1/Th17 immune responses. Therefore, this report suggests that ITK inhibition could be an effective strategy to halt renal dysfunction associated with AKI.

Elevated expression of toll-like receptor 4 is associated with NADPH oxidase-induced oxidative stress in B cells of children with autism.

Autism spectrum disorder (ASD) is a childhood disorder with neurodevelopmental dysfunction which manifests as impairment in social behavior and communication skills. B cells play an important role in immune dysfunction where toll-like receptor 4 (TLR4) may contribute through oxidative inflammatory process. TLR4 related signaling and oxidative stress have been reported in the periphery of ASD subjects, however it has not been evaluated in peripheral B cells of ASD subjects and compared with typically developing control (TDC) children. This study evaluated TLR4 expression and related signaling [Bruton's tyrosine kinase (BTK), spleen tyrosine kinase (SYK), NF-kB, NADPH oxidase (NOX2), nitrotyrosine, superoxide dismutase (SOD)] in ASD and TDC subjects. Current investigation in B cells shows that ASD subjects have increased TLR4 expression and oxidative stress as exhibited by upregulated NOX2 and nitrotyrosine expression as compared to TDC subjects. B cell relevant pathways, BTK/SYK/NF-kB were also upregulated in B cells of ASD group. Treatment with TLR4 agonist, LPS led to upregulation of NOX2 and nitrotyrosine in B cells of ASD whereas it had no significant effect on TDC subjects. Treatment with NF-kB inhibitor caused inhibition of LPS-induced upregulation of NOX2 and nitrotyrosine in B cells of ASD. Therefore, current investigation proposes the notion that TLR4 expression is elevated in B cells which is associated with increased NF-kB signaling and oxidant stress in ASD subjects. In short, peripheral B cells could contribute to systemic oxidative inflammation and contribute to the immune dysfunction in ASD.

Protease activated receptor-2 mediated upregulation of IL-17 receptor signaling on airway epithelial cells is responsible for neutrophilic infiltration during acute exposure of house dust mite allergens in mice.

Asthma, a chronic inflammatory disease affecting the airways is primarily caused due to immune system dysfunction. Different inhaled allergens such as house dust mites (HDM), fungi, cockroach allergens are the main contributors to allergic asthma. Protease activated receptor-2 (PAR-2) signaling plays an important role in allergic asthma through modulation of immune mediators in airway epithelial cells (AECs). Interleukin-17A (IL-17A) signals via subunits of IL-17 receptor (IL-17R), i.e. interleukin-17 receptor A (IL-17RA) and interleukin-17 receptor C (IL-17RC), and plays a necessary role in neutrophilic infiltration in response to infectious/allergenic stimuli, however it is not known if PAR-2 activation affects IL-17A/IL-17R signaling during acute exposure to house dust mite (HDM) allergens. Therefore, our study exposed mice to HDM allergens for five days and evaluated its effect on IL-17A/IL-17R signaling, chemokine/cytokines and neutrophilic inflammation in mice. Our study shows that HDM allergens upregulate IL-17A levels in the lung and IL-17RA/IL-17RC expression in AECs. PAR-2 activation by trypsin also upregulates neutrophilic influx and IL-17A/IL-17R signaling in the lung. Upregulated IL-17A/IL-17R signaling was associated with increased BAL neutrophils, pulmonary MPO activity and proinflammatory chemokines and cytokines (IL-23, IL-6, and MCP-1 in AECs/lung) in HDM exposed mice. Further, HDM-induced IL-17A, IL-17R and chemokines/cytokines were attenuated by PAR-2 antagonist, ENMD-1068. Furthermore, HDM-primed mice treated with IL-17A had greater neutrophilic inflammation and higher levels of inflammatory cytokines/chemokines than PBS-exposed mice treated with IL-17A. This proposes that acute exposure to HDM allergens activate AECs at a very early stage where PAR-2/IL-17R signaling serves a crucial role in neutrophilic inflammation.

Short chain fatty acid, acetate ameliorates sepsis-induced acute kidney injury by inhibition of NADPH oxidase signaling in T cells.

Sepsis affects millions of people worldwide and is associated with acute kidney injury (AKI). Innate and adaptive immune cells have been shown to play an important role in AKI through release of various inflammatory mediators which include reactive oxidant species (ROS). Acetate, a short chain fatty acid produced by gut bacteria has anti-inflammatory properties and has also been shown to modulate oxidative stress in different immune cells. Effects of acetate have been shown to be both GPR43 dependent and independent in different cells/tissues. However, the role of acetate on T cell NADPH oxidase (NOX2)/ROS signaling remains unexplored during sepsis-induced AKI. Therefore, the current study investigated the effect of acetate on sepsis-induced AKI parameters and T cell oxidant-antioxidant balance. Our results show that acetate ameliorates sepsis-induced AKI as reflected by a decrease in serum, creatinine/blood urea nitrogen and renal myeloperoxidase activity/lipid peroxides and restoration of kidney tubular structure. Moreover, acetate administration was associated with correction of oxidant-antioxidant imbalance in T cells during sepsis-induced AKI. Acetate produced its inhibitory effects on NOX2/ROS signaling via attenuation of histone deacetylase activity in T cells which was induced during AKI. Overall, the data suggest that acetate might be beneficial during sepsis-induced AKI by restoration of oxidant-antioxidant balance in T cells.

Plasticizer, di(2-ethylhexyl)phthalate (DEHP) enhances cockroach allergen extract-driven airway inflammation by enhancing pulmonary Th2 as well as Th17 immune responses in mice.

In recent decades, there has been a gradual increase in the prevalence of asthma. Various factors including environmental pollutants have contributed to this phenomenon. Plasticizer, di(2-ethylhexyl)phthalate (DEHP) is one of the commonest environmental pollutants due to its association with plastic products. DEHP gets released from plastic products easily leading to respiratory exposure in humans. As a consequence, DEHP is associated with allergic asthma in humans and animals. DEHP is reported to act as an adjuvant in ovalbumin-induced mouse models of asthma at high doses. However, these studies mostly looked into the role of DEHP on Th2 cytokines/eosinophilic inflammation without investigating the role of airway epithelial cells (AECs)/dendritic cells (DCs)/Th17 cells. Its adjuvant activity with natural allergens such as cockroach allergens at tolerable daily intake needs to be explored. Cockroach allergens and DEHP may be inhaled together due to their coexistence in work place as well as household environments. Therefore, effect of DEHP was assessed in cockroach allergens extract (CE)-induced mouse model of asthma. Airway inflammation, histopathology, mucus secretion, and immune responses related to Th2/Th17/DCs and AECs were assessed in mice with DEHP exposure alone and in combination with CE. Our study shows that DEHP converts CE-induced eosinophilic inflammation into mixed granulocytic inflammation by promoting Th2 as well as Th17 immune responses. This was probably due to downregulation of E-cadherin in AECs, and enhancement of costimulatory molecules (MHCII/CD86/CD40)/pro-inflammatory cytokines (IL-6/MCP-1) in DCs by DEHP. This suggests that DEHP facilitates development of mixed granulocytic airway inflammation in the presence of a natural allergen.