Beneficial effect of recombinant human growth hormone on the intestinal mucosa barrier of septic rats

Deletion of SOCS2 Reduces Post-Colitis Fibrosis via Alteration of the TGFβ Pathway

Inflammatory bowel disease (IBD) is an immunologically mediated chronic intestinal disorder. Growth hormone (GH) administration enhances mucosal repair and decreases intestinal fibrosis in patients with IBD. In the present study, we investigated the effect of cellular sensitivity to GH via suppressor of cytokine signaling 2 (SOCS2) deletion on colitis and recovery. To induce colitis, wild type and SOCS2 knockout (SOCS2−/−) mice were treated with 3% dextran sodium sulphate (DSS), followed by a recovery period. SOCS2−/− mice showed higher disease activity during colitis with increased mRNA expression of the pro-inflammatory cytokines nitric oxide synthase 2 (NOS2) and interleukin 1 β (IL1-β). At recovery time point, SOCS2−/− showed better recovery with less fibrosis measured by levels of α-SMA and collagen deposition. Protein and mRNA expressions of transforming growth factor beta β1 (TGF-β1) receptors were significantly lower in SOCS2−/− mice compared to wild-type littermates. Using an in vivo bromodeoxyuridine (BrdU) proliferation assay, SOCS2−/− mice showed higher intestinal epithelial proliferation compared to wild-type mice. Our results demonstrated that deletion of the SOCS2 protein results in higher growth hormone sensitivity associated with higher pro-inflammatory signaling; however, it resulted in less tissue damage with less fibrotic lesions and higher epithelial proliferation, which are markers of GH-protective effects in IBD. This suggests a pleiotropic effect of SOCS2 and multiple cellular targets. Further study is required to study role of SOCS2 in regulation of TGFβ-mothers against the decapentaplegic homolog (Smad) pathway.

Growth Hormone Resistance-Special Focus on Inflammatory Bowel Disease

Growth hormone (GH) plays major anabolic and catabolic roles in the body and is important for regulating several aspects of growth. During an inflammatory process, cells may develop a state of GH resistance during which their response to GH stimulation is limited. In this review, we will emphasize specific mechanisms governing the formation of GH resistance in the active phase of inflammatory bowel disease. The specific molecular effects mediated through individual inflammatory mediators and processes will be highlighted to provide an overview of the transcriptional, translational and post-translational inflammation-mediated impacts on the GH receptor (GHR) along with the impacts on GH-induced intracellular signaling. We also will review GH’s effects on mucosal healing and immune cells in the context of experimental colitis, human inflammatory bowel disease and in patients with short bowel syndrome.

Intestinal barrier function and the brain-gut axis. Adv Exp Med Biol. 2014;817:73-113. [PMID: 24997030 DOI: 10.1007/978-1-4939-0897-4_4]

The luminal-mucosal interface of the intestinal tract is the first relevant location where microorganism-derived antigens and all other potentially immunogenic particles face the scrutiny of the powerful mammalian immune system. Upon regular functioning conditions, the intestinal barrier is able to effectively prevent most environmental and external antigens to interact openly with the numerous and versatile elements that compose the mucosal-associated immune system. This evolutionary super system is capable of processing an astonishing amount of antigens and non-immunogenic particles, approximately 100 tons in one individual lifetime, only considering food-derived components. Most important, to develop oral tolerance and proper active immune responses needed to prevent disease and inflammation, this giant immunogenic load has to be managed in a way that physiological inflammatory balance is constantly preserved. Adequate functioning of the intestinal barrier involves local and distant regulatory networks integrating the so-called brain-gut axis. Along this complex axis both brain and gut structures participate in the processing and execution of response signals to external and internal changes coming from the digestive tract, using multidirectional pathways to communicate. Dysfunction of brain-gut axis facilitates malfunctioning of the intestinal barrier, and vice versa, increasing the risk of uncontrolled immunological reactions that may trigger mucosal and brain low-grade inflammation, a putative first step to the initiation of more permanent gut disorders. In this chapter, we describe the structure, function and interactions of intestinal barrier, microbiota and brain-gut axis in both healthy and pathological conditions.

CANDIDATE GENES FOR LIMITING CHOLESTATIC INTESTINAL INJURY IDENTIFIED BY GENE EXPRESSION PROFILING

The lack of bile flow from the liver into the intestine can have devastating complications including hepatic failure, sepsis and even death. This pathologic condition known as cholestasis can result from etiologies as diverse as total parenteral nutrition (TPN), hepatitis and pancreatic cancer. The intestinal injury associated with cholestasis has been shown to result in decreased intestinal resistance, increased bacterial translocation and increased endotoxemia. Anecdotal clinical evidence suggests a genetic predisposition to exaggerated injury. Recent animal research on two different strains of inbred mice demonstrating different rates of bacterial translocation with different mortality rates supports this premise. In this study, a microarray analysis of intestinal tissue following common bile duct ligation (CBDL) performed under general anesthesia on these same two strains of inbred mice was done with the goal of identifying the potential molecular mechanistic pathways responsible. Over 500 genes were increased more than 2.0 fold following CBDL. The most promising candidate genes included MUPs, Serpina1a and LCN-2. RT-PCR validated the microarray results for these candidate genes. In an in vitro experiment using differentiated intestinal epithelial cells, inhibition of MUP-1 by siRNA resulted in increased intestinal epithelial cell permeability. Diverse novel mechanisms involving the growth hormone pathway, the acute phase response and the innate immune response are thus potential avenues for limiting cholestatic intestinal injury. Changes in gene expression were at times found to be not only due to the CBDL but also due to the murine strain. Should further studies in cholestatic patients demonstrate inter-individual variability similar to what we have shown in mice, then a "personalized medicine" approach to cholestatic patients may become possible.

Recombinant human growth hormone improves survival and protects against acute lung injury in murine Staphylococcus aureus sepsis

OBJECTIVE

To investigate whether recombinant human growth hormone (rhGH) reduces mortality and protects against Staphylococcus aureus sepsis-induced acute lung injury.

METHODS

The bacteria-positive rate of blood smears and bacteria colony counts in bacteria plate culture, TNFalpha and IL-10 plasma levels, lung injury score, expression of intercellular adhesion molecule-1 (ICAM-1) as well as activation of nuclear factor-kappa B (NF-kappaB) in the lungs were determined 6, 12 and 24 h after 140 KM mice were injected with physiologic saline (i.p. group C, n = 20); S. aureus E311122 (1.75 x 10(12) cfu/L, 40 ml/kg, i.p. group S, n = 60); or S. aureus (as group S) with a subsequent treatment of rhGH (1.0 U kg(-1) day(-1)), i.m. group T, n = 60). The cumulative survival rate of an additional 15 mice from each group was followed for 7 days post S. aureus injection.

RESULTS

rhGH treatment significantly increased IL-10 plasma levels and the 7-day cumulative survival rate, whereas the bacteria-positive rate of blood smears, bacteria colony counts in bacteria plate cultures, lung injury score, ICAM-1 and NF-kappaB expression in the lungs were significantly reduced. In addition, rhGH treatment significantly suppressed the S. aureus sepsis-induced elevation of TNFalpha plasma levels.

CONCLUSIONS

These results indicate an ability of rhGH to prevent S. aureus sepsis-induced acute lung injury in mice, which may be attributed to attenuation of increased plasma TNFalpha levels, and elevated IL-10 plasma levels as well as reduced ICAM-1 expression and inhibited NF-kappaB activity in the lungs.