Hemorrhage-induced intestinal damage is complement-independent in Helicobacter hepaticus-infected mice

Innate immunity and immunotherapy for hemorrhagic shock

Hemorrhagic shock (HS) is a shock result of hypovolemic injury, in which the innate immune response plays a central role in the pathophysiology ofthe severe complications and organ injury in surviving patients. During the development of HS, innate immunity acts as the first line of defense, mediating a rapid response to pathogens or danger signals through pattern recognition receptors. The early and exaggerated activation of innate immunity, which is widespread in patients with HS, results in systemic inflammation, cytokine storm, and excessive activation of complement factors and innate immune cells, comprised of type II innate lymphoid cells, CD4⁺ T cells, natural killer cells, eosinophils, basophils, macrophages, neutrophils, and dendritic cells. Recently, compelling evidence focusing on the innate immune regulation in preclinical and clinical studies promises new treatment avenues to reverse or minimize HS-induced tissue injury, organ dysfunction, and ultimately mortality. In this review, we first discuss the innate immune response involved in HS injury, and then systematically detail the cutting-edge therapeutic strategies in the past decade regarding the innate immune regulation in this field; these strategies include the use of mesenchymal stem cells, exosomes, genetic approaches, antibody therapy, small molecule inhibitors, natural medicine, mesenteric lymph drainage, vagus nerve stimulation, hormones, glycoproteins, and others. We also reviewed the available clinical studies on immune regulation for treating HS and assessed the potential of immune regulation concerning a translation from basic research to clinical practice. Combining therapeutic strategies with an improved understanding of how the innate immune system responds to HS could help to identify and develop targeted therapeutic modalities that mitigate severe organ dysfunction, improve patient outcomes, and reduce mortality due to HS injury.

The other Helicobacters

The last year has seen an interesting and important collection of evidence presented in the field of the "other" than Helicobacter pylori Helicobacters. Associations with adult ulcerative colitis and biliary/hepatic disease have been described. New insights into the immune response and subsequent pathogenesis associated with infection have also been published. Genomic advances include description of new and unique species and the complete genome description for both Helicobacter felis and Helicobacter suis. Molecular studies have also elucidated the mechanism of action of some functional components of these organisms.

Macrophage-produced IL-12p70 mediates hemorrhage-induced damage in a complement-dependent manner

Hemorrhage and hemorrhagic shock instigate intestinal damage and inflammation. Multiple components of the innate immune response, including complement and neutrophil infiltration, are implicated in this pathology. To investigate the interaction of complement activation and other components of the innate immune response during hemorrhage, we treated mice after hemorrhage with CR2-fH, a targeted inhibitor of the alternative complement pathway and assessed intestinal damage and inflammation 2 h after hemorrhage. In wild-type mice, CR2-fH attenuated hemorrhage-induced, midjejunal damage and inflammation as determined by decreased mucosal damage, macrophage infiltration, leukotriene B4, IL-12p40, and TNF-[alpha] production. The critical nature of intestinal macrophage infiltration and activation in the response to hemorrhage was further determined using mice pretreated with clodronate-containing liposomes. The absence of either macrophages or IL-12p70 attenuated intestinal damage. These data suggest that complement activation and macrophage infiltration with IL-12p70 production are critical to hemorrhage-induced midjejunal damage and inflammation.

Helicobacter infection alters MyD88 and Trif signalling in response to intestinal ischaemia-reperfusion

Ischaemia-reperfusion-induced intestinal injury requires both Toll-like receptor 4 (TLR4) signalling through myeloid differentiation primary response gene (88) (MyD88) and complement activation. As a common Gram-negative intestinal pathogen, Helicobacter hepaticus signals through TLR4 and upregulates the complement inhibitor, decay accelerating factor (DAF; CD55). Since ischaemia-reperfusion (IR) injury is complement dependent, we hypothesized that Helicobacter infection may alter IR-induced intestinal damage. Infection increased DAF transcription and subsequently decreased complement activation in response to IR without altering intestinal damage in wild-type mice. Ischaemia-reperfusion induced similar levels of DAF mRNA expression in uninfected wild-type, MyD88(-/-) or TIR-domain-containing adaptor-inducing interferon-β (Trif)-deficient mice. However, during infection, IR-induced DAF transcription was significantly attenuated in Trif-deficient mice. Likewise, IR-induced intestinal damage, complement component 3 deposition and prostaglandin E(2) production were attenuated in Helicobacter-infected, Trif-deficient but not MyD88(-/-) mice. While infection attenuated IR-induced cytokine production in wild-type and MyD88(-/-) mice, there was no further decrease in Trif-deficient mice. These data indicate distinct roles for MyD88 and Trif in IR-induced inflammation and suggest that chronic, undetected infections, such as Helicobacter, alter the use of the adaptor proteins to induce damage.

Helicobacter spp. other than Helicobacter pylori

Over the last 12 months, new insights into the association of non-Helicobacter pylori Helicobacters with a range of human diseases in children and adults, including hepatobiliary disease, Crohn's disease, sepsis, and gastric disease were published. Studies investigating the presence of non-H. pylori Helicobacters in domestic animals reinforce previous findings that cats and dogs harbor gastric Helicobacter species and thus may be an important source of these organisms in humans. The confounding effect of enterohepatic Helicobacters on the outcome of biomedical research was investigated in several studies and led to recommendations that animals should be screened prior to performing experiments. A number of important and novel investigations regarding pathogenic mechanisms and immune responses to enterohepatic Helicobacters were conducted. Genomic advances in non-H. pylori Helicobacters included description of the complete genome of Helicobacter canadensis, delineation of two Helicobacter bilis genomospecies, and identification of a novel cis-regulatory RNA. New insights concerning growth conditions, biochemical characterization, and the effect of certain dietary compounds on Helicobacter spp. have also been reported.