Altered expression of CXCR1 (IL-8R) in macrophages utilizing cell surface TNFR1 and IL-1 receptor during Staphylococcus aureus infection

IL-10 in combination with IL-12 and TNF-α attenuates CXCL8/CXCR1 axis in peritoneal macrophages of mice infected with Staphylococcus aureus through the TNFR1-IL-1R-NF-κB pathway

Overexpression of Staphylococcus aureus mediated CXCL8/CXCR1 axis is a major cause of sepsis and severe inflammatory diseases. This chemokine acts conjointly with various pro-inflammatory and anti-inflammatory cytokines that govern the severity of inflammation. The effects of different combinations of exogenous cytokines on CXCR1 expression in macrophages remain undetermined. Exogenous cytokine and anti-inflammatory cytokine therapy had been used to modulate CXCL8 and CXCR1 expression in peritoneal macrophages. Male Swiss albino mice were inoculated with live S. aureus (10⁶ cells/ mouse) for the development of infection. Exogenous cytokines (TNF-α, IL-12, IFN-γ and IL-10) were administered intraperitoneally (single or combination) 24 h post S. aureus infection. The mice were sacrificed and peritoneal macrophages were isolated three days post infection. CXCL8, IL-12, IL-10 secretion, ROS generation and the bacterial phagocytic process had been evaluated. Western blot was used to study the expressions of TNFR1, IL-1R, CXCR1 and NF-κB. TNF-α, IL-12 and IFN-γ treatments aggravated CXCL8 and CXCR1 expression in the macrophages of infected mice. TNF-α + IFN-γ treatment was a major inducer of nitric oxide release and mediated maximum bacterial killing. IL-12 + TNF-α treatment was most potent in increasing ROS, CXCL8/CXCR1 expression through increased levels of TNFR1, IL-1R and NF-κB activation. IL-10 reversed the effects of exogenous cytokines but also impaired the bacterial clearance phenomenon in peritoneal lavage. Treatment with IL-12 + TNF-α + IL-10 was most effective in ameliorating oxidative stress, reduced CXCL8 release and expression levels of TNFR1, IL-1R, and NF-κB. Concludingly, IL-12 + TNF-α + IL-10 treatment mitigated CXCL8/CXCR1 expression and inflammatory signalling via downregulation of TNFR1-IL-1R-NF-κB pathway in peritoneal macrophages and inflammatory sequelae during S. aureus infection.

Neutralization of TNF-α and IL-1β Regulates CXCL8 Production through CXCL8/CXCR1 Axis in Macrophages during Staphylococcus aureus Infection

Anti-cytokine therapy is widely acknowledged as an anti-inflammatory technique to treat varied infectious diseases. TNF-α and IL-1β are major cytokines that regulate every aspect of the inflammatory process. However, the effects of single or dual cytokine neutralization on S. aureus mediated CXCL8 secretion and CXCR1 expression in murine peritoneal macrophages remained noninvestigated. Thus we aimed to explore the effects of kinetic-dose dependent neutralization of TNF-α and IL-1β using specific anti-cytokine antibodies and its influential impact on the CXCL8/CXCR1 axis at different stages of S. aureus (30, 60, and 90 min) infection. The murine peritoneal macrophages were isolated and infected with viable S. aureus followed by subsequent addition of anti-TNF-α and anti-IL-1β into the medium. The treated cells were centrifuged and lysate and supernatant collected for various experiments. The ROS generation was measured and cytokine production was estimated by ELISA. The expression of TNFR1, IL-1R, CXCR1, signaling molecules (NF-κB and JNK) were evaluated by Western blot. The role of single or dual cytokine neutralization on intracellular bacterial phagocytosis had also been analyzed by confocal microscopy. Dual cytokine neutralization significantly suppressed ROS, cytokines, CXCL8 secretion, and intracellular bacterial count compared to single cytokine neutralization and it was more apparent at 90 min post S. aureus infection. There was a drastic reduction in TNFR1, IL-1R, and CXCR1 expression on macrophage surface due to reduced expression of downstream signaling molecules, NF-κB and JNK. Hence dual cytokine neutralization was more effectual compared to single cytokine neutralization in the downregulation of S. aureus induced CXCR1 expression.

Curcumin ameliorates Staphylococcus aureus-induced mastitis injury through attenuating TLR2-mediated NF-κB activation

PROBLEM

It has long been known that Staphylococcus aureus (S. aureus, serotype CP8) is associated with clinical mastitis in cows, and recent scientific studies have shown that curcumin (CUR) is effective in anti-inflammatory. However, the mechanism of action of curcumin on S. aureus-induced cows has not been fully understood. Therefore, this study investigated whether curcumin could improve the inflammation response in mice mastitis and to clarify the possible mechanism.

METHOD

of study: A mouse mastitis model was established. The mice were administered curcumin (125 mg/kg), ciprofloxacin (130 mg/kg, CIP), and water (model group) for 5 days.

RESULTS

CUR and CIP treatment prevented the S. aureus-induced mouse mastitis increase the levels of IL-2, IL-10, and IFN-γ and decrease levels of IL-6, IL-8, and TNF-α. Additionally, RT-PCR results showed that 20 μg/mL curcumin inhibited the mRNA expression of TNF-α, IL-6, IL-1β, TRAF6 and MEKK1 in murine mammary epithelial cells (MMECs). Likewise, Western blotting results showed that CUR inhibited the expression of TRAF6 and MEKK1.

CONCLUSION

These results indicated that CUR is superior to CIP in the prevention of mastitis, and the mechanism may be that the curative effect of CUR inhibits TLR-2 mediated NF-κB signaling pathway in mouse mastitis.

Regulation of Staphylococcus aureus-induced CXCR1 expression via inhibition of receptor mobilization and receptor shedding during dual receptor (TNFR1 and IL-1R) neutralization

Our earlier studies proposed a radically new idea suggesting interdependency between TNF-α/TNFR1 and IL-1β/IL-1R pathways in modulation of Staphylococcus aureus-induced CXCL8/CXCR1 axis. However, the effects of inhibition of cytokine receptor mobilization at intracellular level and surface TNFR1 and IL-1R shedding on S. aureus-induced CXCR1 expression have not been studied so far in peritoneal macrophages. This study aimed to investigate the role of inhibition of receptor mobilization from the intracellular pool (using brefeldin A) and surface receptor shedding (using TAPI-1) on CXCR1 expression during dual receptor (TNFR1 plus IL-1R) neutralization in peritoneal macrophages isolated from wild-type Swiss Albino mice. Release of superoxide anion, nitric oxide, and hydrogen peroxide was measured and cytokine production was done by ELISA. Expression of surface receptors (TNFR1, IL-1R, and CXCR1) and inflammatory mediators was studied by Western blot. It was observed that S. aureus-infected macrophages showed elevated ROS production, secretion of TNF-α, IL-1β, and CXCL8, along with increased expression of surface receptors (TNFR1, IL-1R, and CXCR1), and inflammatory markers (iNOS and COX-2) compared with control or treated groups (p < 0.05). However, prior treatment of macrophages with BFA or TAPI-1 in the presence of anti-TNFR1 antibody and IRAP during S. aureus infection showed significant reduction of all these parameters (p < 0.05). We can conclude that targeting of TNFR1 and IL-1R (with major focus on surface expression study) either through blockage of intracellular receptor trafficking pathway or via surface receptor shedding diminishes TNFR1/IL-1R interaction and consequently downregulates CXCR1 expression along with inflammatory signalling pathways during bacterial infections.