The Role of Aryl Hydrocarbon Receptor in Interleukin-23-Dependent Restoration of Interleukin-22 Following Ethanol Exposure and Burn Injury

Abstract

Objectives T-helper (Th)-17 lymphocytes play a crucial role in maintenance and regulation of gut immunity. Our laboratory has demonstrated that acute ethanol (EtOH) exposure before burn injury results in intestinal T cell suppression and enhanced bacterial translocation. Background To extend these studies, we examined the effects of EtOH exposure and burn injury on Th17 responses within intestinal lymphoid Peyer’s patches (PP). We further investigated whether restitution of interleukin (IL)-23 enhances PP cell IL-17 and IL-22 after EtOH and burn injury. Methods Male mice, approximately 25 g, were gavaged with EtOH (2.9 mg/kg) before receiving an approximately 12.5% total body surface area full thickness burn. One day postinjury, PP mixed cells were cultured in the presence of plate-bound anti-CD3/soluble anti-CD28 in the presence or absence of IL-23 for 48 hours. Supernatants were harvested for IL-17 and IL-22 levels. Results When combined with EtOH intoxication, burn injury significantly decreased IL-17 and IL-22, as compared with sham injury. IL-23 treatment successfully increased levels of IL-22 but not IL-17. This restoration was prevented when PP cells were treated with CH-223191, an aryl hydrocarbon receptor inhibitor. To further delineate the mechanism of differential IL-17 and IL-22 suppression, PP cells were treated with phorbol 12-myristate 13-acetate (PMA) and ionomycin, which signal via protein kinase C (PKC) and calcium flux. Treatment with PMA and ionomycin significantly prevented the decrease in IL-17 but not IL-22 after EtOH exposure and burn injury. Conclusions These findings suggest that IL-23-mediated restoration of IL-22 is aryl hydrocarbon receptor dependent, whereas IL-17 requires activation of protein kinase C and intracellular calcium signaling.

Intestine Immune Homeostasis After Alcohol and Burn Injury

“…However, IL-17 levels were not significantly influenced by IL-23 restitution, suggesting that IL-23 differentially regulates IL-17 and IL-22 following ethanol and burn injury. Furthermore, our data demonstrate a role for AHR in IL-23-mediated restoration of IL-22, and indicate that AHR may be involved in the well-described IL-23/ROR-γt pathway (123; 144). Recent studies demonstrate that AHR may interact with multiple signaling molecules, including STAT proteins and members of the ROR family (189; 191).…”

“…Furthermore, there are significant decreases in intestinal IL-22, RegIIIβ and RegIIIγ expression, which are accompanied with increases in intestinal permeability and bacterial overgrowth in animals receiving ethanol intoxication combined with burn injury. Treatment of animals with rIL-22 normalizes the expression of RegIIIβ and RegIIIγ in the small intestine, and prevents the increase in intestinal permeability, as well as reduces intestinal bacterial growth following ethanol and burn injury (123; 144). Together, these findings suggest that Th17 cells play a critical role in the maintenance of the intestinal mucosal barrier and immune responses after ethanol and burn injury.…”

Interleukin-22 Prevents Microbial Dysbiosis and Promotes Intestinal Barrier Regeneration Following Acute Injury

“…We have previously established that IL-22 production from T cells in gut associated lymphoid tissue (GALT) is significantly reduced following the combined injury(9). In addition, administration of recombinant IL-22 was shown to reduce intestine leakiness, suggesting that IL-22 may be beneficial following acute injury(8).…”

“…Studies have demonstrated that approximately half of patients admitted to burn units have detectable blood ethanol levels, and that these patients exhibit higher rates of infection and greater incidence of mortality (6, 7). We have shown that ethanol intoxication exacerbates the suppression of intestinal T cells and potentiates small bowel barrier disruption, and increases Gram-negative bacterial overgrowth within one day after burn injury (8, 9). More recently, we have discovered changes to the microbiome in our rodent model of burn injury directly reflect the changes observed to the microbiome of hospitalized burn patients (10).…”

“…We have previously shown a significant reduction in IL-22 production from T cells in gut-associated lymphoid tissues following the combined injury (9). Restorative treatment with IL-22 following ethanol and burn injury resulted in substantially reduced gut barrier leakiness, and mitigated Gram-negative bacterial overgrowth (8).…”