Ingested (oral) SST inhibits EAE

Somatostatin-SSTR3-GSK3 modulates human T-cell responses by inhibiting OXPHOS

Introduction

Somatostatin (SST) is a peptide hormone primarily synthesized in the digestive and nervous systems. While its impact on the endocrine system is well-established, accumulating evidence suggests a crucial role for SST and its analogues in modulating immune responses. Despite this, the precise mechanism through which SST regulates T cells has remained largely unknown.

Methods

To elucidate the impact of SST on human T cells, we conducted a series of experiments involving cell culture assays, molecular analyses, and metabolic profiling. Human T cells were treated with SST, and various parameters including proliferation, cytokine production, and metabolic activities were assessed. Additionally, we employed pharmacological inhibitors and genetic manipulations to dissect the signaling pathways mediating SST's effects on T cells.

Results

We showed that SST diminishes T-cell proliferation by influencing IL-2 production and T-cell mitochondrial respiration, while having no discernible impact on TCR-induced glycolysis. Our findings also identified that the regulatory influence of SST on T-cell responses and metabolism is contingent on its receptor, SSTR3. Moreover, we demonstrated that SST governs T-cell responses and metabolism by acting through the T-cell metabolic checkpoint GSK3.

Discussion

Our study provides novel insights into the immunoregulatory function of SST in human T cells, highlighting the complex interplay between hormonal signaling and immune regulation. Understanding the molecular mechanisms underlying SST's effects on T cells may offer therapeutic opportunities for manipulating immune responses in various pathological conditions.

Type I interferon mediated induction of somatostatin leads to suppression of ghrelin and appetite thereby promoting viral immunity in mice

Loss of appetite (anorexia) is a typical behavioral response to infectious diseases that often reduces body weight. Also, anorexia can be observed in cancer and trauma patients, causing poor quality of life and reduced prospects of positive therapeutic outcomes. Although anorexia is an acute symptom, its initiation and endocrine regulation during antiviral immune responses are poorly understood. During viral infections, plasmacytoid dendritic cells (pDCs) produce abundant type I interferon (IFN-I) to initiate first-line defense mechanisms. Here, by targeted ablation of pDCs and various in vitro and in vivo mouse models of viral infection and inflammation, we identified that IFN-I is a significant driver of somatostatin (SST). Consequently, SST suppressed the hunger hormone ghrelin that led to severe metabolic changes, anorexia, and rapid body weight loss. Furthermore, during vaccination with Modified Vaccinia Ankara virus (MVA), the SST-mediated suppression of ghrelin was critical to viral immune response, as ghrelin restrained the production of early cytokines by natural killer (NK) cells and pDCs, and impaired the clonal expansion of CD8⁺ T cells. Thus, the hormonal modulation of ghrelin through SST and the cytokine IFN-I is fundamental for optimal antiviral immunity, which comes at the expense of calorie intake.

Hormones in experimental autoimmune encephalomyelitis (EAE) animal models

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) in which activated immune cells attack the CNS and cause inflammation and demyelination. While the etiology of MS is still largely unknown, the interaction between hormones and the immune system plays a role in disease progression, but the mechanisms by which this occurs are incompletely understood. Several in vitro and in vivo experimental, but also clinical studies, have addressed the possible role of the endocrine system in susceptibility and severity of autoimmune diseases. Although there are several demyelinating models, experimental autoimmune encephalomyelitis (EAE) is the oldest and most commonly used model for MS in laboratory animals which enables researchers to translate their findings from EAE into human. Evidences imply that there is great heterogeneity in the susceptibility to the induction, the method of induction, and the response to various immunological or pharmacological interventions, which led to conflicting results on the role of specific hormones in the EAE model. In this review, we address the role of endocrine system in EAE model to provide a comprehensive view and a better understanding of the interactions between the endocrine and the immune systems in various models of EAE, to open up a ground for further detailed studies in this field by considering and comparing the results and models used in previous studies.

Ingested (oral) anti-IL-12/23 inhibits EAE

BACKGROUND

Blocking the activity of IL-12/23 can inhibit autoimmune diseases such as psoriasis.

OBJECTIVE

We examined whether an antibody against IL-12/23, ustekinumab (UTZ) (Stelera®), used clinically in psoriasis would have similar anti-inflammatory effects in EAE after oral administration.

DESIGN/METHODS

B6 mice were immunized with MOG peptide 35-55 and gavaged with isotype IgG control or UTZ during ongoing disease. Splenocytes, CD4(+) T cells or macrophages/monocyte lineage cells (CD11b(+)) from control fed or UTZ fed mice were adoptively transferred into active MOG peptide 35-55 immunized recipient mice during ongoing disease. Actively fed and recipient mice were examined for disease inhibition, inflammation, and cytokine responses.

RESULTS

Ingested (oral) UTZ inhibited ongoing disease and decreased inflammation. Adoptively transferred cells from UTZ fed donors protected against actively induced disease and decreased inflammation. Oral UTZ decreased pro-inflammatory cytokines Th1-like cytokines IL-2, IL-12, IFN-γ, IL-17 (Teff) and TNF-α in UTZ fed mice and increased counter-regulatory cytokines IL-4, IL-10 and IL-13 in recipients of donor cells from UTZ fed mice.

CONCLUSIONS

Ingested (orally administered) UTZ can inhibit disease, CNS inflammation, decrease pro-inflammatory Th1-like and Th17 cytokines and increase Th2-like anti-inflammatory cytokines.

Ingested (oral) tocilizumab inhibits EAE

BACKGROUND

Blocking the activity of IL-6 can inhibit autoimmune diseases such as rheumatoid arthritis and Crohn's disease.

OBJECTIVE

We examined whether an antibody against IL-6, tocilizumab (TCZ) (Actemra®), used clinically in rheumatoid arthritis (RA) would have similar anti-inflammatory effects in EAE after oral administration.

DESIGN/METHOD

B6 mice were immunized with MOG peptide 35-55 and gavaged with control saline or TCZ during ongoing disease. Splenocytes, CD4(+) T cells or macrophages/monocyte lineage cells (CD11b(+)) from control fed or TCZ fed mice were adoptively transferred into active MOG peptide 35-55 immunized recipient mice during ongoing disease. Actively fed and recipient mice were examined for disease inhibition, inflammation, and cytokine responses.

RESULTS

Ingested (oral) TCZ inhibited ongoing disease and decreased inflammation. Adoptively transferred cells from TCZ fed donors protected against actively induced disease and decreased inflammation. There was a decrease in IL-6 in actively treated spleen, decrease in TNF-α, Th1-like cytokine IL-12 and increase in Th2-like cytokine IL-10 in active fed and adoptively treated recipients.

CONCLUSIONS

Ingested (orally administered) TCZ can inhibit disease, CNS inflammation, decrease pro-inflammatory Th1-like cytokines and increase Th2-like anti-inflammatory cytokines.

Role of mesenteric lymph pathway in the effects of exogenous somatostatin against early intestinal injury after ischemia-reperfusion in rats

Intestinal ischemia-reperfusion (I/R)-induced gut injury remains a challenge for critically ill patients. This study aims to test whether mesenteric lymph pathway is involved in intestinal I/R injury and whether somatostatin (SST) affects mesenteric lymph pathway after mesenteric reperfusion. Intestinal I/R rats were treated with SST-14 by intravenous injection combined with intraperitoneal injection before occlusion of the SMA until the end of the experiment. When intestinal I/R injury treated with SST, the volumes of mesenteric lymph flow at the 6th h after reperfusion following intestinal ischemia were increased ([0.55±0.24] ml/h vs [0.25±0.09] ml/h, p<0.05) and the number of intestinal lymphocytes per milliliter ([2.30±0.72]×10⁷/ml vs [1.16±0.63]×10⁷/ml, p<0.05) was also increased, which caused the number of intestinal lymphocytes output at the same period of time was significantly increased compared with intestinal I/R group ([1.33±0.88]×10⁷/h vs [0.28±0.15]×10⁷/h, p<0.05). Meanwhile, the number of ⁵¹Cr-lymphocytes migration from systemic circulation to the effector sites in GALT was significantly increased ([1.93±0.23]×10⁵/h vs [0.90±0.25]×10⁵/h, p<0.05), although the percentage of ⁵¹Cr-lymphocytes in the effector sites ([1.45±0.26]% vs [3.23±1.69]%, p<0.05) was sharply decreased compared with intestinal I/R group. The accompanying decreases of the endotoxin concentration ([0.038±0.017] EU/mL vs [0.110±0.028] EU/mL, compared with intestinal I/R group p<0.05) and the TNF-α levels ([37.50±10.45] ρg/ml) vs ([74.93±14.77] ρg/ml), compared with intestinal I/R group p<0.05) in mesenteric lymph and the improvement of vital organ dysfunction happened during the early intestinal I/R injury. Suppression of gut-derived toxic mediators reaching systemic circulation and increases of the number of lymphocytes homing to the effector sites in GALT to strengthen the effective immune responses in intestinal mucosa account for the protective effects of exogenous SST against early intestinal I/R injury.

Somatostatin preserved blood brain barrier against cytokine induced alterations: possible role in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory neurological disorder associated with demyelination, impaired blood brain barrier (BBB), axonal damage and neuronal loss. In the present study, we measured somatostatin (SST) and tumor necrosis factor-α (TNF-α) like immunoreactivity in CSF samples from MS and non-MS patients. We also examined the role of SST in cytokines and lipopolysaccharide (LPS)-induced damage to the BBB using human brain endothelial cells in culture. Most of the cerebrospinal fluid (CSF) samples studied from definite MS patients exhibited lower somatostatin (SST)-like immunoreactivity and higher expression of TNF-α in comparison to non-MS patients. Treatment of cells with cytokines and LPS blocked SST secretion and decreased SST expression. Human brain endothelial cells expressed all five somatostatin receptors (SSTRs) with increased expression of SSTR2 and 4 upon treatment with cytokines and LPS. Cytokines and LPS-induced disruption of the tight junction proteins Zonula occludens (ZO-1) organization was restored in presence of SST, SSTR2 or SSTR4 selective agonists. Furthermore, inflammation induced changes in extracellular signal-regulated kinases (ERK1/2 and ERK5) signaling and altered expression of endothelial and inducible nitric oxide synthase are modulated in presence of SST. These data indicate that decreased levels of SST contribute to failure of the BBB in MS.

Ingested (oral) thyrotropin releasing factor (TRH) inhibits EAE

BACKGROUND

Ingested immunoactive proteins type I IFN, SIRS peptide 1-21, α-MSH, ACTH, SST inhibit clinical attacks and inflammation in acute EAE by decreasing Th1-like cytokines, increasing Th2-like cytokines or increasing T(reg) cell frequencies.

OBJECTIVE

We examined whether another protein, thyrotropin releasing factor (TRH), would have similar anti-inflammatory effects in EAE after oral administration.

DESIGN/METHODS

B6 mice were immunized with MOG peptide 35-55 and gavaged with control saline or TRH during ongoing disease. Splenocytes from mock fed or TRH fed mice were adoptively transferred into active MOG peptide 35-55 immunized recipient mice during ongoing disease.

RESULTS

Ingested (oral) TRH inhibited ongoing disease and decreased inflammation. Adoptively transferred cells from TRH fed donors protected against actively induced disease and decreased inflammation. In actively fed mice, oral TRH decreased IL-17 and TNF-α cytokines in both the spleen and the CNS. In recipients of donor cells from TRH fed mice there was a reduction of Th1 and Th17 and induction of Th2-like IL-13 cytokines in both the spleen and CNS. Oral TRH decreased clinical score and decreased inflammatory foci in both actively fed and recipients of actively fed mice. There was no significant increase in T(reg) cell frequencies in actively fed or recipients of TRH fed donor cells.

CONCLUSIONS

Ingested (orally administered) TRH can inhibit clinical disease, inhibit CNS inflammation by decreasing Th1-like, Th17 and TNF-α cytokines and increasing Th2-like cytokines (IL-13) in the CNS.

Ingested (oral) neuropeptide Y inhibits EAE

BACKGROUND

Ingested immunoactive proteins, type I IFN, SIRS peptide 1-21, α-MSH, ACTH, and SST inhibit clinical attacks and inflammation in acute EAE by decreasing Th1-like cytokines, increasing Th2-like cytokines or increasing T(reg) cell frequencies.

OBJECTIVE

We examined whether another protein, neuropeptide Y, would have similar anti-inflammatory effects in EAE after oral administration.

DESIGN/METHODS

B6 mice were immunized with MOG peptide 35-55 and gavaged with control saline or NPY during ongoing disease. Splenocytes from mock fed or NPY fed mice were adoptively transferred into active MOG peptide 35-55 immunized recipient mice during ongoing disease.

RESULTS

Ingested (oral) NPY inhibited ongoing disease, and decreased inflammation. Adoptively transferred cells from NPY fed donors protected against actively induced disease and decreased inflammation. In actively fed mice, oral NPY decreased Th1-like cytokines and increased Th2-like IL-13 cytokines in both the spleen and the CNS. In recipients of donor cells from NPY fed mice there was a reduction of Th1 and Th17 and induction of Th2-like IL-13 cytokines in both the spleen and CNS. Oral NPY decreased clinical score and decreased inflammatory foci in both actively fed and recipients of actively fed mice. There was no significant increase in T(reg) cell frequencies in actively fed or recipients of NPY fed donor cells.

CONCLUSIONS

Ingested (orally administered) NPY can inhibit clinical disease, inhibit CNS inflammation by decreasing Th17 and Th1-like cytokines and increasing Th2-like cytokines in the CNS.

Diffuse endocrine system, neuroendocrine tumors and immunity: what's new?

During the last two decades, research into the modulation of immunity by the neuroendocrine system has flourished, unravelling significant effects of several neuropeptides, including somatostatin (SRIH), and especially cortistatin (CST), on immune cells. Scientists have learnt that the diffuse neuroendocrine system can regulate the immune system at all its levels: innate immunity, adaptive immunity, and maintenance of immune tolerance. Compelling studies with animal models have demonstrated that some neuropeptides may be effective in treating inflammatory disorders, such as sepsis, and T helper 1-driven autoimmune diseases, like Crohn's disease and rheumatoid arthritis. Here, the latest findings concerning the neuroendocrine control of the immune system are discussed, with emphasis on SRIH and CST. The second part of the review deals with the immune response to neuroendocrine tumors (NETs). The anti-NET immune response has been described in the last years and it is still being characterized, similarly to what is happening for several other types of cancer. In parallel with investigations addressing the mechanisms by which the immune system contrasts NET growth and spreading, ground-breaking clinical trials of dendritic cell vaccination as immunotherapy for metastatic NETs have shown in principle that the immune reaction to NETs can be exploited for treatment.