Somatostatin modulates T cells development in adult rat thymus

Enteroendocrine cells-sensory sentinels of the intestinal environment and orchestrators of mucosal immunity

The intestinal epithelium must balance efficient absorption of nutrients with partitioning commensals and pathogens from the bodies' largest immune system. If this crucial barrier fails, inappropriate immune responses can result in inflammatory bowel disease or chronic infection. Enteroendocrine cells represent 1% of this epithelium and have classically been studied for their detection of nutrients and release of peptide hormones to mediate digestion. Intriguingly, enteroendocrine cells are the key sensors of microbial metabolites, can release cytokines in response to pathogen associated molecules and peptide hormone receptors are expressed on numerous intestinal immune cells; thus enteroendocrine cells are uniquely equipped to be crucial and novel orchestrators of intestinal inflammation. In this review, we introduce enteroendocrine chemosensory roles, summarize studies correlating enteroendocrine perturbations with intestinal inflammation and describe the mechanistic interactions by which enteroendocrine and mucosal immune cells interact during disease; highlighting this immunoendocrine axis as a key aspect of innate immunity.

Expression of somatostatin and cDNA cloning in the thymus of the African ostrich

The thymus in addition to being a central lymphoid organ is also an endocrine organ which produces various neuropeptides that influence the function of this gland. Somatostatin is a neuropeptide that was isolated initially in the hypothalamus and which inhibits the release of growth hormone. The distribution of somatostatin-producing cells and the sequence of somatostatin have been determined in many species. In the present study, we investigated the expression of somatostatin in the thymus of the African ostrich and its sequence by reverse-transcriptase polymerase chain reaction and immunohistochemistry. The results showed that somatostatin mRNA was expressed in the thymus and somatostatin immunoreative cells were distributed in both the cortical and medullary regions of the thymus. Results of cDNA cloning revealed that the nucleotide sequence and the encoded protein of African ostrich somatostatin were 348 bases and 116 amino acids in length and that it is highly conserved to that of other reported species. These findings indicated that the somatostatin expressed in the thymus of ostrich might play an important role in the function of the gland. In addition, this research has provided novel molecular data allowing further study of somatostatin in the ostrich.

Changes in thymus size, cellularity and relation between thymocyte subpopulations in young adult rats induced by somatostatin-14

The role of somatostatin on inhibition of both normal and tumor cell cycle, secretion of endocrine and exocrine cells, as well as induction apoptosis is well documented. However, its effect on T cell development and thymic structure is not fully clarified. In order to investigate the influence of somatostatin in vivo on the thymus structure and T cell development, the young adult Albino Oxford male rats were intracerebroventriculary treated with somatostatin-14. We examined the thymus compartments and its cellularity, through assessment of morphometric parameters by stereological method, and the relation between thymocytes subpopulations, over expression of CD4, CD8 and T-cell receptor (TCR) alpha beta by flow cytometry. Additionally, we also determined the body and thymus weight of the rats, during the first three months of life, to define the time of SRIH-14 application. A decrease of relative thymus weight from the fourth weeks of postnatal life, and an unchanged relative thymus weight obtained in treated group indicates that SRIH-14 in young adult rats inhibits growth of whole organism, not only thymus. The changes in the absolute number and numerical density of cortical thymocytes indicate that SRIH-14 alters the true lymphoid tissue. SRIH-14 changes relation between thymocyte subsets, increase number of CD4(-)CD8(-)TCR alpha beta(-) and CD4(-)CD8(+)TCR alpha beta(hi) thymocyte subsets as well as the CD4(-)CD8(-)TCR alpha beta(low/hi) thymocytes, while decrease number of CD4(+)CD8(+) TCR alpha beta(-/low/hi) thymocyte subsets. These results indicate that somatostatin-14 is not involved in the control of the physiologic involution of the thymus, although induces thymic weight loss through the reduction of true lymphoid tissue. In addition, changes in frequency of thymocyte subpopulations, especially immature cells, indicate that SRIH-14 modulates thymocytes development and maturation.