Norepinephrine suppresses IFN-γ and TNF-α production by murine intestinal intraepithelial lymphocytes via the β₁ adrenoceptor

Exploring the complex interplay: gut microbiome, stress, and leptospirosis

Leptospirosis, a re-emerging zoonotic disease, remains a significant global health concern, especially amid floods and disasters such as the Kakhovka Dam destruction. As is known, the stress that occurs in the conditions of military conflicts among civilian and military personnel significantly affects susceptibility to infectious diseases and possibly even influences their course. This review aims to explore how the gut microbiome and stress mediators (such as catecholamines and corticosteroids) might impact the leptospirosis disease course. The review opens new horizons for research by elucidating the connections between the gut microbiome, stress, and leptospirosis.

β-adrenoreceptor-triggered PKA activation negatively regulates the innate antiviral response

Upon viral infection, cytoplasmic pattern recognition receptors detect viral nucleic acids and activate the adaptor protein VISA/MAVS- or MITA/STING-mediated innate antiviral response. Whether and how the innate antiviral response is regulated by neuronal endocrine functions is unclear. Here, we show that viral infection reduced the serum levels of the β-adrenergic hormones epinephrine and norepinephrine as well as the cellular levels of their receptors ADRB1 and ADRB2. We further show that an increase in epinephrine/norepinephrine level inhibited the innate antiviral response in an ADRB1-/2-dependent manner. Mechanistically, epinephrine/norepinephrine stimulation activated the downstream kinase PKA, which catalyzed the phosphorylation of MITA at S241, S243 and T263, inhibiting MITA activation and suppressing the innate immune response to DNA virus. In addition, phosphorylation of VISA at T54 by PKA antagonized the innate immune response to RNA virus. These findings reveal the regulatory mechanisms of innate antiviral responses by epinephrine/norepinephrine and provide a possible explanation for increased host susceptibility to viral infection in stressful and anxiety-promoting situations.

Differential effect of intermittent hypoxia and sleep fragmentation on PD-1/PD-L1 upregulation

Immunosurveillance is compromised in patients with obstructive sleep apnea (OSA) as reflected by overexpression of the programmed death cell receptor and its ligand (PD-1/PD-L1) coinhibitory axis. However, the contributions of intermittent hypoxia (IH) and sleep fragmentation (SF) are unclear. We therefore evaluated the expression of PD-1 and PD-L1 on immune cells from mice subjected to IH or SF, and in human cells exposed to IH, oxidative stress, or both conditions. Six-week-old male C57BL/6J mice were exposed to either IH or SF using previously established in vivo models. Moreover, human peripheral blood mononuclear cells (PBMC) were cultured overnight under normoxia, IH, hydrogen peroxide (H2O2), or both. Murine splenocytes and human PBMC were isolated, and labeled using surface-specific antibodies for flow cytometry analysis. Compared to control mice, IH induced higher expression of PD-L1 on F4/80 cells and of PD-1 on CD4+ and CD8+ T-cells, whereas no significant changes emerged after SF. In vitro models of IH and oxidative stress showed similar changes for expression of PD-L1 on human monocytes and PD-1 on CD4+ T-cells. Furthermore, H2O2 increased PD-1 expression on CD8+ T-cells, compromising their cytotoxic capacity assessed by perforin expression, similar to IH. No evidence of synergistic effects was apparent. Therefore, PD-1/PD-L1 upregulation reported in patients with OSA appears to be preferentially mediated by IH rather than SF.

Autonomic regulation of T-lymphocytes: Implications in cardiovascular disease

The nervous and immune systems both serve as essential assessors and regulators of physiological function. Recently, there has been a great interest in how the nervous and immune systems interact to modulate both physiological and pathological states. In particular, the autonomic nervous system has a direct line of communication with immune cells anatomically, and moreover, immune cells possess receptors for autonomic neurotransmitters. This circumstantial evidence is suggestive of a functional interplay between the two systems, and extensive research over the past few decades has demonstrated neurotransmitters such as the catecholamines (i.e. dopamine, norepinephrine, and epinephrine) and acetylcholine have potent immunomodulating properties. Furthermore, immune cells, particularly T-lymphocytes, have now been found to express the cellular machinery for both the synthesis and degradation of neurotransmitters, which suggests the ability for both autocrine and paracrine signaling from these cells independent of the nervous system. The details underlying the functional interplay of this complex network of neuroimmune communication are still unclear, but this crosstalk is suggestive of significant implications on the pathogenesis of a number of autonomic-dysregulated and inflammation-mediated diseases. In particular, it is widely accepted that numerous forms of cardiovascular diseases possess imbalanced autonomic tone as well as altered T-lymphocyte function, but a paucity of literature exists discussing the direct role of neurotransmitters in shaping the inflammatory microenvironment during the progression or therapeutic management of these diseases. This review seeks to provide a fundamental framework for this autonomic neuroimmune interaction within T-lymphocytes, as well as the implications this may have in cardiovascular diseases.

Distribution of non-myelinating Schwann cells and their associations with leukocytes in mouse spleen revealed by immunofluorescence staining

The nervous system and the immune system communicate extensively with each other in order to maintain homeostasis and to regulate the immune response. The peripheral nervous system (PNS) communicates specifically with the immune system according to local interactions, including the “hardwiring” of sympathetic/parasympathetic (efferent) and sensory nerves (afferent) to lymphoid tissue and organs. To reveal this type of bidirectional neuroimmune interaction at the microscopic level, we used immunofluorescent staining of glial fibrillary acidic protein (GFAP) coupled with confocal microscopy/3D reconstruction to reveal the distribution of nonmyelinating Schwann cells (NMSCs) and their interactions with immune cells inside mouse spleen. Our results demonstrate i) the presence of an extensive network of NMSC processes in all splenic compartments including the splenic nodules, periarteriolar lymphoid sheath (PALS), marginal zone, trabecula, and red pulp; ii) the close association of NMSC processes with blood vessels (including central arteries and their branches, marginal sinuses, penicillar arterioles and splenic sinuses); iii) the close “synapse-like” interaction/association of NMSC processes with various subsets of dendritic cells (DCs; e.g., CD4⁺CD11c⁺ DCs, B220⁺CD11c⁺ DCs, and F4/80⁺ CD11c⁺ DCs), macrophages (F4/80⁺), and lymphocytes (B cells, CD4⁺ T helper cells). Our novel findings concerning the distribution of NMSCs and NMSC-leukocytes interactions inside mouse spleen should improve our understanding of the mechanisms through which the PNS affects cellular- and humoral-mediated immune responses in a variety of health conditions and infectious/non-infectious diseases.

Neonatal Colonic Inflammation Epigenetically Aggravates Epithelial Inflammatory Responses to Injury in Adult Life

BACKGROUND & AIMS

Early life adversity is considered a risk factor for the development of gastrointestinal diseases, including inflammatory bowel disease. We hypothesized that early life colonic inflammation causes susceptibility to aggravated overexpression of interleukin (IL)1β.

METHODS

We developed a 2-hit rat model in which neonatal inflammation (NI) and adult inflammation (AI) were induced by trinitrobenzene sulfonic acid.

RESULTS

Aggravated immune responses were observed in NI + AI rats, including a sustained up-regulation of IL1β and other cytokines. In parallel with exacerbated loss of inhibitor of kappa B alpha expression, NI + AI rats showed hyperacetylation of histone H4K12 and increased V-Rel Avian Reticuloendotheliosis Viral Oncogene Homolog A binding on the IL1B promoter, accompanied by high levels of norepinephrine/epinephrine. Propranolol, a β-blocker, markedly ameliorated the inflammatory response and IL1β overexpression by mitigating against epigenetic modifications. Adrenalectomy abrogated NI-induced disease susceptibility whereas yohimbine sensitized the epithelium for exacerbated immune response. The macrophages of NI rats produced more IL1β than controls after exposure to lipopolysaccharide (LPS), suggesting hypersensitization; incubation with LPS plus Foradil (Sigma, St. Louis, MO), a β2-agonist, induced a greater IL1β expression than LPS alone. Epinephrine and Foradil also exacerbated LPS-induced IL1β activation in human THP-1-derived macrophages, by increasing acetylated H4K12, and these increases were abrogated by propranolol.

CONCLUSIONS

NI sensitizes the colon epithelium for exacerbated IL1β activation by increasing stress hormones that induce histone hyperacetylation, allowing greater access of nuclear factor-κB to the IL1B promoter and rendering the host susceptible to aggravated immune responses. Our findings suggest that β blockers have a therapeutic potential for inflammatory bowel disease susceptibility and establish a novel paradigm whereby NI induces epigenetic susceptibility to inflammatory bowel disease.

Obesity in IBD: epidemiology, pathogenesis, disease course and treatment outcomes

Incidence of IBD is rising in parallel with overweight and obesity. Contrary to conventional belief, about 15-40% of patients with IBD are obese, which might contribute to the development of IBD. Findings from cross-sectional and retrospective cohort studies are conflicting on the effect of obesity on natural history and course of IBD. Most studies are limited by small sample size, low event rates, non-validated assessment of disease activity and lack robust longitudinal follow-up and have incomplete adjustment for confounding factors. The effect of obesity on the efficacy of IBD-related therapy remains to be studied, though data from other autoimmune diseases suggests that obesity results in suboptimal response to therapy, potentially by promoting rapid clearance of biologic agents leading to low trough concentrations. These data provide a rationale for using weight loss interventions as adjunctive therapy in patients with IBD who are obese. Obesity also makes colorectal surgery technically challenging and might increase the risk of perioperative complications. In this Review, we highlight the existing literature on the epidemiology of obesity in IBD, discuss its plausible role in disease pathogenesis and effect on disease course and treatment response, and identify high-priority areas of future research.

Mitochondrial Superoxide Signaling Contributes to Norepinephrine-Mediated T-Lymphocyte Cytokine Profiles

Norepinephrine (NE) produces multifaceted regulatory patterns in T-lymphocytes. Recently, we have shown that NE utilizes redox signaling as evidenced by increased superoxide (O2●-) causally linked to the observed changes in these cells; however, the source of this reactive oxygen species (ROS) remains elusive. Herein, we hypothesized that the source of increased O2●- in NE-stimulated T-lymphocytes is due to disruption of mitochondrial bioenergetics. To address this hypothesis, we utilized purified mouse splenic CD4+ and CD8+ T-lymphocytes stimulated with NE and assessed O2●- levels, mitochondrial metabolism, cellular proliferation, and cytokine profiles. We demonstrate that the increase in O2●- levels in response to NE is time-dependent and occurs at later points of T-lymphocyte activation. Moreover, the source of O2●- was indeed the mitochondria as evidenced by enhanced MitoSOX Red oxidation as well as abrogation of this signal by the addition of the mitochondrial-targeted O2●--scavenging antioxidant MitoTempol. NE-stimulated T-lymphocytes also demonstrated decreased mitochondrial respiratory capacity, which suggests disruption of mitochondrial metabolism and the potential source of increased mitochondrial O2●-. The effects of NE in regards to redox signaling appear to be adrenergic receptor-dependent as specific receptor antagonists could reverse the increase in O2●-; however, differential receptors regulating these processes were observed in CD4+ versus CD8+ T-lymphocytes. Finally, mitochondrial O2●- was shown to be mechanistic to the NE-mediated T-lymphocyte phenotype as supplementation of MitoTempol could reverse specific changes in cytokine expression observed with NE treatment. Overall, these studies indicate that mitochondrial metabolism and O2●--mediated redox signaling play a regulatory role in the T-lymphocyte response to NE.

Effect of tyrosine hydroxylase overexpression in lymphocytes on the differentiation and function of T helper cells

The aim of the present study was to examine the effect of the overexpression of tyrosine hydroxylase (TH), a rate-limiting enzyme for the synthesis of catecholamines (CAs), in lymphocytes on the differentiation and function of T helper (Th) cells. A recombinant TH overexpression plasmid (pEGFP-N1-TH) was constructed and transfected into mesenteric lymphocytes using nucleofection technology. These cells were stimulated with concanavalin A (Con A) for 48 h and then examined for TH expression and CA content, as well as for the percentage of Th1 and Th2 cells, cytokine concentrations and for the levels of signaling molecules. The lymphocytes overexpressing TH also expressed higher mRNA and protein levels of TH, and synthesized more CAs, including norepinephrine (NE), epinephrine (E) and dopamine (DA) than the mock-transfected control cells. TH gene overexpression in the lymphocytes reduced the percentage of interferon-γ (IFN-γ)-producing CD4+ cells and the ratio of CD4+IFN-γ+/CD4+IL-4+ cells, as well as the percentages of CD4+CD26+ and CD4+CD30+ cells and the ratio of CD4+CD26+/CD4+CD30+ cells. TH overexpression also reduced the secretion of IFN-γ and tumor necrosis factor (TNF) from lymphocytes. Moreover, NE inhibited the Con A-induced lymphocyte proliferation and decreased both cyclic adenosine monophosphate (cAMP) levels and p38 mitogen-activated protein kinase (MAPK) expression in the lymphocytes. Our findings thus indicate that TH gene overexpression promotes the polarization and differentiation of CD4+ cells towards Th2 cells, and this effect is mediated by the cAMP and p38 MAPK signaling pathways.

[Radioligand Method of Assessment of β-Adrenoceptor's Activity on Human T-Lymphocytes]

We proposed a new method of evaluation of beta-receptor's activity on the surface of human T-lymphocytes based on the radioligand method. Optimal conditions for evaluation of specific binding to β2-adrenoceptors of 0.5 fmol ligand per 1 million cells using [125I]-cyanopindolol were found. The possibility of using of β2-adrenoceptor's activity assessment in clinical settings was demonstrated on human T-lymphocyte.

Sympathetic-mediated activation versus suppression of the immune system: consequences for hypertension

It is generally well-accepted that the immune system is a significant contributor in the pathogenesis of hypertension. Specifically, activated and pro-inflammatory T-lymphocytes located primarily in the vasculature and kidneys appear to have a causal role in exacerbating elevated blood pressure. It has been proposed that increased sympathetic nerve activity and noradrenaline outflow associated with hypertension may be primary contributors to the initial activation of the immune system early in the disease progression. However, it has been repeatedly demonstrated in many different human and experimental diseases that sympathoexcitation is immunosuppressive in nature. Moreover, human hypertensive patients have demonstrated increased susceptibility to secondary immune insults like infections. Thus, it is plausible, and perhaps even likely, that in diseases like hypertension, specific immune cells are activated by increased noradrenaline, while others are in fact suppressed. We propose a model in which this differential regulation is based upon activation status of the immune cell as well as the resident organ. With this, the concept of global immunosuppression is obfuscated as a viable target for hypertension treatment, and we put forth the concept of focused organ-specific immunotherapy as an alternative option.

Targeting ß2 adrenergic receptors regulate human T cell function directly and indirectly

It is well-established that central nervous system activation affects peripheral blood mononuclear cell (PBMCs) function through the release of the catecholamines (Epi) and norepinephrine (NE), which act on ß2-adrenergic receptors (ß2AR). However, most studies have used non-specific stimulation of cells rather than antigen-specific responses. Likewise, few studies have parsed out the direct effects of ß2AR stimulation on T cells versus indirect effects via adrenergic stimulation of antigen presenting cells (APC). Here we report the effect of salmeterol (Sal), a selective ß2AR agonist, on IFN-γ(+) CD4 and IFN-γ(+) CD8 T cells following stimulation with Cytomegalovirus lysate (CMVL-strain AD169) or individual peptides spanning the entire region of the HCMV pp65 protein (pp65). Cells were also stimulated with Staphylococcal enterotoxin B. Additionally, we investigated the effect of Epi and Sal on cytotoxic cell killing of transfected target cells at the single cell level using the CD107a assay. The results show that Sal reduced the percentage of IFN-γ(+) CD4 and IFN-γ(+) CD8 T cells both when applied directly to isolated T cells, and indirectly via treatment of APC. These inhibitory effects were mediated via a ß2 adrenergic-dependent pathway and were stronger for CD8 as compared to CD4 T cells. Similarly, the results show that Sal suppressed cytotoxicity of both CD8 T and NK cells in vitro following stimulation with Chinese hamster ovary cell line transfected with MICA(*009) (T-CHO) and the human erythromyeloblastoid leukemic (K562) cell line. The inhibitory effect on cytotoxicity following stimulation with T-CHO was stronger in NK cells compared with CD8 T cells. Thus, targeting the ß2AR on lymphocytes and on APC leads to inhibition of inflammatory cytokine production and target cell killing. Moreover, there is a hierarchy of responses, with CD8 T cells and NK cells inhibited more effectively than CD4 T cells.

Redox-regulated suppression of splenic T-lymphocyte activation in a model of sympathoexcitation

Sympathoexcitation, increased circulating norepinephrine, and elevated levels of reactive oxygen species are driving forces underlying numerous cardiovascular diseases, including hypertension. However, the effects of elevated norepinephrine and subsequent reactive oxygen species production in splenic T-lymphocytes during hypertension are not currently understood. We hypothesized that increased systemic levels of norepinephrine inhibits the activation of splenic T-lymphocytes via redox signaling. To address this hypothesis, we examined the status of T-lymphocyte activation in spleens of a mouse model of sympathoexcitation-driven hypertension (ie, norepinephrine infusion). Splenic T-lymphocytes from norepinephrine-infused mice demonstrated decreased proliferation accompanied by a reduction in interferon gamma and tumor necrosis factor-α production as compared with T-lymphocytes from saline-infused mice. Additionally, norepinephrine directly inhibited splenic T-lymphocyte proliferation and cytokine production ex vivo in a dose-dependent manner. Furthermore, norepinephrine caused an increase in G1 arrest in norepinephrine-treated T-lymphocytes, and this was accompanied by a decrease in pro-growth cyclin D3, E1, and E2 mRNA expression. Interestingly, norepinephrine caused an increase in cellular superoxide, which was shown to be partially causal to the inhibitory effects of norepinephrine, as antioxidant supplementation (ie, Tempol) to norepinephrine-infused mice moderately restored T-lymphocyte growth and proinflammatory cytokine production. Our findings indicate that suppression of splenic T-lymphocyte activation occurs in a norepinephrine-driven model of hypertension due to, at least in part, an increase in superoxide. We speculate that further understanding of how norepinephrine mediates its inhibitory effects on splenic T-lymphocytes may elucidate novel pathways for therapeutic mimicry to suppress T-lymphocyte-mediated inflammation in an array of diseases.

Aluminum chloride- and norepinephrine-induced immunotoxicity on splenic lymphocytes by activating β2-AR/cAMP/PKA/NF-κB signal pathway in rats

We found in our previous research that aluminum (Al) exposure induced immunotoxicity on spleen and increased norepinephrine (NE) content in serum from rats. However, it is unclear how NE is involved in the AlCl3 immunotoxicity on rats. Therefore, this experiment was designed to explore the mechanism of AlCl3 and NE-induced immunotoxicity on the splenic lymphocytes. Eighty male Wistar rats were orally exposed to AlCl3 (0, 64, 128, and 256 mg/kg BW) through drinking water for 120 days. Al contents in brain and spleen; NE contents in serum and in the hypothalamus; β2-AR density; cAMP content; β2-AR, PKA, and NF-κB mRNA expression levels; and protein expressions of PKA and nuclear NF-κB in splenic lymphocytes of AlCl3-treated rats were examined. The results showed that AlCl3 increased NE content in serum, the β2-AR density, the β2-AR and PKA (C-subunits) mRNA expression levels, cAMP content and the PKA (C-subunits) protein expression levels in lymphocytes, whereas, decreased NE content in the hypothalamus, the NF-κB (p65) mRNA expression level and nuclear NF-κB (p65) protein expression level in lymphocytes. These results indicated that the accumulated AlCl3 in spleen and the increased NE in serum induced the immunotoxicity on splenic lymphocytes by activating β2-AR/cAMP/PKA/NF-κB signal pathway in rats.

Mild cold-stress depresses immune responses: Implications for cancer models involving laboratory mice

Physiologically accurate mouse models of cancer are critical in the pre-clinical development of novel cancer therapies. However, current standardized animal-housing temperatures elicit chronic cold-associated stress in mice, which is further increased in the presence of tumor. This cold-stress significantly impacts experimental outcomes. Data from our lab and others suggest standard housing fundamentally alters murine physiology, and this can produce altered immune baselines in tumor and other disease models. Researchers may thus underestimate the efficacy of therapies that are benefitted by immune responses. A potential mediator, norepinephrine, also underlies stress pathways common in mice and humans. Therefore, research into mechanisms connecting cold-stress and norepinephrine signaling with immune depression in mice could highlight new combination therapies for humans to simultaneously target stress while stimulating anti-tumor immunity.

Effects of norepinephrine on immune functions of cultured splenic lymphocytes exposed to aluminum trichloride

The aim of this study was to investigate the effect of norepinephrine (NE) on spleen lymphocytes exposed to aluminum trichloride (AlCl3). In this experiment, lymphocytes were isolated from spleens of healthy Wistar rats weighing about 130 g and cultured with RPMI-1640 medium containing the final concentration of 0.552 mmol/L AlCl3. NE was added to the cultured cells at the final concentrations of 0 (control group), 0.1 (low-dose group), 1 (mid-dose group), and 10 (high-dose group) nmol/L. No addition of both AlCl3 and NE serviced as blank (BG). The T lymphocyte proliferation; the contents of IL-2, TNF-α, and T lymphocyte subsets; immunoglobulin G (IgG) and intracellular cyclic adenosine monophosphate (cAMP) concentrations; and β2-adrenergic receptor (β2-AR) density were measured at the end of the culture. The result showed that NE decreased T lymphocyte proliferation and the contents of IL-2, TNF-α, and T lymphocyte subsets whereas increased the concentrations of IgG and intracellular cAMP and β2-AR density of the lymphocyte exposed to AlCl3. AlCl3 exposure without adding NE showed the similar impacts on these measures compared with BG. The results suggested that NE aggravated AlCl3 immunotoxicity on the lymphocytes and disordered the immune functions of the lymphocyte through the β2-AR-cAMP signal pathway.

Effects of intraepithelial lymphocyte-derived cytokines on intestinal mucosal barrier function

The mucosal surface of the gastrointestinal tract directly interacts with the mucosal lumen, which is continuously exposed to foreign antigens. Specialized intraepithelial lymphocytes (IELs), located between the basolateral surfaces of the epithelial cells, are important as the first line of defense against microbes as well as for their role in the maintenance of epithelial barrier homeostasis. Although IELs are mainly composed of T cells, they are phenotypically and functionally distinct from T cells in peripheral blood or the spleen. Not only are IELs stimulated by the antigens of the intestinal lumen but are they also stimulated by regulatory immune cells. The integrity of the intestinal mucosal barrier is closely tied to the IEL function. Cytokines produced by IELs modulate the cellular functions that trigger the downstream signaling pathways and mediate the barrier homeostasis. In this review, we will address the broad spectrum of cytokines that are derived from IELs and the functional regulation of these cytokines on the intestinal barrier.

Statins directly suppress cytokine production in murine intraepithelial lymphocytes

Statins, inhibitors of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, are known not only as cholesterol-lowering agents but also as anti-inflammatory mediators. However, their regulatory effect on intestinal mucosal immunity remains unclear. The present study examined the possible direct effects of statin on intestinal intraepithelial lymphocytes (IELs), the front line cells of the intestinal mucosal immune system. Murine IELs were isolated from the small intestines of C57BL/6 mice. IELs activated with anti-CD3/CD28 monoclonal antibodies produced interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-2, and IL-4 in significant numbers; however, they did not produce IL-5. Both simvastatin and lovastatin suppressed IEL production of IFN-γ, TNF-α, IL-2, and IL-4 in a dose-dependent manner, whereas 48-h treatment with high concentrations (5 × 10(-5)M) of simvastatin and lovastatin did not affect the number of IELs. The suppressive effect of the simvastatin was significantly restored by the addition of mevalonate, farnesyl pyrophosphate ammonium salt, and geranylgeranyl pyrophosphate ammonium salt, which are downstream metabolites of HMG-CoA. These findings suggest that statins have direct suppressive effects on the production of T helper 1-cytokines and IL-4 in IELs; these effects are associated with inhibition of the mevalonate pathway to some extent.