Modulation of type I IL-1 receptor and IL-1 beta mRNA expression followed by endotoxin treatment in the corticotropin-releasing hormone-deficient mouse

IL-1R1 deficiency impairs liver regeneration after 2/3 partial hepatectomy in aged mice

Inflammation has a dual effect: it can protect the body and destroy tissue and cell as well. The purpose of this experiment was to determine the role of IL-1R1 in liver regeneration (LR) after partial hepatectomy (PH) in aged mice. The wild-type (WT, n = 36) and the IL-1R1 knockout (KO, n = 36) 24-month-old C57BL/6J mice underwent two-thirds PH; 33 WT mice underwent sham operation. Liver coefficient was calculated by liver/body weight. The mRNA and protein expressions of genes were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting methods, respectively. Compared with WT mice, liver coefficient was lower in the IL-1R1 KO aged mice at 168 and 192 h (p = 0.039 and p = 0.027). The mRNA transcription of inflammation-related genes and cell cycle-associated genes decreased or delayed. The protein expressions of proliferation-related marker PCNA and proliferation-associated signaling pathway components JNK1, NF-κB and STAT3 reduced or retarded. There was stronger activation of proapoptotic proteins caspase-3, caspase-8 and BAX in the IL-1R1 KO mice at different time points (p < 0.05 or p < 0.01). IL-1R1 KO reduced inflammation and caused impaired liver regeneration after 2/3 partial hepatectomy in aged mice. Maintaining proper inflammation may contribute to regeneration after liver partly surgical resection in the elderly.

Salient type 1 interleukin 1 receptor expression in peripheral non-immune cells

Interleukin 1 is a pleiotropic cytokine that mediates diverse functions through its receptor, type I interleukin 1 receptor (IL-1R1). Most previous studies have focused on the expression and function of IL-1R1 in immune cells. Here we performed a comprehensive mapping of IL-1R1 distribution in multiple peripheral tissues using our IL-1R1 reporter (IL-1R1^GR/GR) mice. This method yielded the highest sensitivity of in situ detection of IL-1R1 mRNA and protein. Besides validating previously reported IL-1R1 expression in the endocrine tissues including pituitary and pancreas, our results refuted previously reported exclusive IL-1R1 expression in neurons of the spinal cord dorsal horn and dorsal root ganglia (DRG). Instead, IL-1R1 expression was detected in endothelial cells within DRG, spinal cord, pancreas, colon, muscles and many immune organs. In addition, gp38⁺ fibroblastic reticular cells (FRCs), rather than tissue macrophages or other immune cells, were found to express high levels of IL-1R1 in colon and many immune organs. A functional test of spleen FRCs showed that they responded rapidly to systemic IL-1β stimulation in vivo. Taken together, this study provides a rigorous re-examination of IL-1R1 expression in peripheral tissues and reveals tissue FRCs as a previously unappreciated novel high IL-1R1-expressing cell type in peripheral IL-1 signaling.

Identification of a novel interaction between corticotropin releasing hormone (Crh) and macroautophagy

In inflammatory bowel disease (IBD), compromised restitution of the epithelial barrier contributes to disease severity. Owing to the complexity in the pathogenesis of IBD, a variety of factors have been implicated in its progress. In this study, we report a functional interaction between macroautophagy and Corticotropin Releasing Hormone (Crh) in the gut. For this purpose we used DSS colitis model on Crh -/- or wild-type (wt) with pharmacological inhibition of autophagy. We uncovered sustained basal autophagy in the gut of Crh -/- mice, which persisted over the course of DSS administration. Autophagy inhibition resulted in partial rescue of Crh -/- mice, while it increased the expression of Crh in the wt gut. Similarly, Crh deficiency was associated with sustained activation of base line autophagy. In vitro models of amino acid deprivation- and LPS-induced autophagy confirmed the in vivo findings. Our results indicate a novel role for Crh in the intestinal epithelium that involves regulation of autophagy, while suggesting the complementary action of the two pathways. These data suggest the intriguing possibility that targeting Crh stimulation in the intestine may provide a novel therapeutic approach to support the integrity of the epithelial barrier and to protect from chronic colitis.

Leptin fails to blunt the lipopolysaccharide-induced activation of the hypothalamic-pituitary-adrenal axis in rats

Obesity is a risk factor for sepsis morbidity and mortality, whereas the hypothalamic-pituitary-adrenal (HPA) axis plays a protective role in the body's defence against sepsis. Sepsis induces a profound systemic immune response and cytokines serve as excellent markers for sepsis as they act as mediators of the immune response. Evidence suggests that the adipokine leptin may play a pathogenic role in sepsis. Mouse endotoxaemic models present with elevated leptin levels and exogenously added leptin increased mortality whereas human septic patients have elevated circulating levels of the soluble leptin receptor (Ob-Re). Evidence suggests that leptin can inhibit the regulation of the HPA axis. Thus, leptin may suppress the HPA axis, impairing its protective role in sepsis. We hypothesised that leptin would attenuate the HPA axis response to sepsis. We investigated the direct effects of an i.p. injection of 2 mg/kg leptin on the HPA axis response to intraperitoneally injected 25 μg/kg lipopolysaccharide (LPS) in the male Wistar rat. We found that LPS potently activated the HPA axis, as shown by significantly increased plasma stress hormones, ACTH and corticosterone, and increased plasma interleukin 1β (IL1β) levels, 2 h after administration. Pre-treatment with leptin, 2 h before LPS administration, did not influence the HPA axis response to LPS. In turn, LPS did not affect plasma leptin levels. Our findings suggest that leptin does not influence HPA function or IL1β secretion in a rat model of LPS-induced sepsis, and thus that leptin is unlikely to be involved in the acute-phase endocrine response to bacterial infection in rats.

Effects of atrazine and chlorpyrifos on the mRNA levels of IL-1 and IFN-γ2b in immune organs of common carp

Atrazine (ATR) and chlorpyrifos (CPF) are widely used in agriculture has resulted in a series of toxicological and environmental problems. The aim of this study was to investigate the effects of ATR, CPF and their mixture on the mRNA levels of interleukin-1β (IL-1β), interleukin receptor I (IL-1RI) and interferon gamma (IFN-γ2b) in both spleen and head kidney of Common carp. In this study, juvenile common carp were exposed to ATR (at concentrations of 4.28, 42.8 and 428 μg/L), CPF (at concentrations of 1.16, 11.6 and 116 μg/L), and their mixture (at concentrations of 1.16, 11.6 and 116 μg/L). The mRNA levels of IL-1β, IL-1R1 and IFN-γ2b in spleen and head kidney were detected by using RT-PCR. Our results indicated that IL-1β, IL-1R1 expression significantly increased after exposure in high concentration ATR, CPF and their mixture, but IFN-γ2b mRNA shown different expression trends. Our results suggested that ATR, CPF and their mixture probably induced damages on spleen and head kidney may be association with increasing IL-1β, IL-1R1 mRNA synthesis. After 20-day recovery test, IL-1β, IL-1R1 and IFN-γ2b mRNA expression remain at high level in majority of the treated groups, we concluded that the restoration of tissue and immune system damage probably needs longer time.

Neuroimmune pharmacology from a neuroscience perspective

The focus of this commentary is to describe how neuroscience, immunology, and pharmacology intersect and how interdisciplinary research involving these areas has expanded knowledge in the area of neuroscience, in particular. Examples are presented to illustrate that the brain can react to the peripheral immune system and possesses immune function and that resident immune molecules play a role in normal brain physiology. In addition, evidence is presented that the brain immune system plays an important role in mediating neurodegenerative diseases, the aging process, and neurodevelopment and synaptic plasticity. The identification of these mechanisms has been facilitated by pharmacological studies and has opened new possibilities for pharmacotherapeutic approaches to the treatment of brain disorders. The emerging field of neuroimmune pharmacology exemplifies this interdisciplinary approach and has facilitated the study of basic cellular and molecular events and disease states and opens avenues for novel therapies.

Cytokines and Brain Injury: Invited Review

The brain reacts to injury or disease by cascades of cellular and molecular responses. Evidence suggests that immune-inflammatory processes are key elements in the physiopathological processes associated with brain injury or damage. Cytokines are among major mediators implicated in these processes. Cytokine responses in the initial phase of brain injury might have a role in aggravating brain damage. However, in later stages, these molecular mediators might contribute to recovery or repair. Hemodynamic stabilization and optimalization of oxygen delivery to the brain remain cornerstones in the management of acute brain injury. New approaches might use anticytokine therapy to limit progression and halt or attenuate secondary brain damage. Progress toward such novel neuroprotection strategies, however, awaits better understanding of the optimal timing and dosing of those neuromodulatory therapies and better knowledge of the numerous interactions of those mediators. This also requires understanding of how and when precisely immune mechanisms shift from noxious to protective or restorative actions.

Effects of PM2.5 collected from Cache Valley Utah on genes associated with the inflammatory response in human lung cells

In January 2004, the normally picturesque Cache Valley in northern Utah made national headlines with the highest PM2.5 levels in the nation. Epidemiological studies linked exposure to particulate air pollution in other locations with stroke and Alzheimer's disease and to early mortality from all causes, cancer, and cardiopulmonary diseases. To determine potential effects of these particles on human health, human bronchial epithelial cells (BEAS-2B) were cultured with PM2.5 collected from various locations in the Cache Valley. These particles were slightly cytotoxic, but more potent than NH4NO3, the major chemical component of Cache Valley PM2.5. Gene expression analysis of PM2.5-exposed cells was performed using microarray and quantitative reverse-transcription polymerase chain reaction (RT-PCR). Among other genes, PM2.5 exposure induced genes and proteins involved in the inflammatory response. Most notably, PM2.5-exposed cells showed significant gene level upregulation of activating receptors to interleukins 1 and 6 (IL-1R1 and IL-6R), as well as concomitant increases in protein. Increases in IL-1 receptor associated kinase-1 (IRAK) protein were observed. PM2.5 exposure resulted in release of IL-6, as well phosphorylated STAT3 protein, providing evidence that PM activates the IL-6/gp130/STAT3 signaling pathway in BEAS-2B cells. IL-20 and major histocompatibility complex peptide class-1 (MICA) were upregulated and cleavage of caspase-12 was detected. In total, our results indicate that Cache Valley PM2.5 produces the upregulation of important cytokine receptors and is able to activate both IL-1R- and IL-6R-mediated signaling pathways in human lung cells. These observations are generally consistent with the adverse effects associated with inhalation of fine particulate matter like PM2.5.

Attenuated stress response to acute lipopolysaccharide challenge and ethanol administration in vasopressin V1b receptor knockout mice

The arginine vasopressin (Avp) 1b receptor (Avpr1b) present on anterior pituitary corticotrophs is involved in the stimulation of adrenocorticotrophic hormone (ACTH) secretion, especially during times of stress. Corticotrophin-releasing hormone (CRH) is considered the major ACTH secretagogue during acute stress whereas Avp appears to be the more dominant mediator of the hypothalamic-pituitary-adrenal (HPA) axis response during chronic stress situations. To investigate the role of the Avpr1b in the HPA axis response to acute stress, we measured ACTH and corticosterone (CORT) plasma levels in Avpr1b knockout (KO) mice and wild-type controls in response to bacterial lipopolysaccharide (LPS) challenge and ethanol (EtOH) administration. Mice deficient in Avpr1b had markedly compromised plasma ACTH and CORT responses to acute (30 min) LPS, but normal ACTH and CORT response to more extended exposure (4 h) to the immune system activator. The plasma ACTH and CORT levels stimulated by intoxicating, sedative doses of EtOH (3.2 and 4 g/kg) were significantly decreased in the Avpr1b KO mice compared to wild-type littermates. Significantly higher EtOH-induced plasma ACTH and CORT secretion was measured in female than in male Avpr1b wild-type mice. There were no differences in the blood alcohol levels following acute EtOH administration in Avpr1b KO or wild-type mice of either gender. Our results clearly suggest that Avpr1b plays a significant role in the HPA axis response to acute immune stress and EtOH intoxication.

Type I interleukin-1 receptor is required for pulmonary responses to subacute ozone exposure in mice

Interleukin (IL)-1, a proinflammatory cytokine, is expressed in the lung after ozone (O(3)) exposure. IL-1 mediates its effects through the type I IL-1 receptor (IL-1RI), the only signaling receptor for both IL-1alpha and IL-1beta. The purpose of this study was to determine the role of IL-1RI in pulmonary responses to O(3.) To that end, wild-type, C57BL/6 (IL-1RI(+/+)) mice and IL-1RI-deficient (IL-1RI(-/-)) mice were exposed to O(3) either subacutely (0.3 ppm for 72 h) or acutely (2 ppm for 3 h). Subacute O(3) exposure increased bronchoalveolar lavage fluid (BALF) protein, interferon-gamma-inducible protein (IP)-10, soluble tumor necrosis factor receptor 1 (sTNFR1), and neutrophils in IL-1RI(+/+) and IL-1RI(-/-) mice. With the exception of IP-10, all outcome indicators were reduced in IL-1RI(-/-) mice. Furthermore, subacute O(3) exposure increased IL-6 mRNA expression in IL-1RI(+/+), but not IL-1RI(-/-) mice. Acute (2 ppm) O(3) exposure increased BALF protein, IL-6, eotaxin, KC, macrophage inflammatory protein (MIP)-2, IP-10, monocyte chemotactic protein-1, sTNFR1, neutrophils, and epithelial cells in IL-1RI(+/+) and IL-1RI(-/-) mice. For IL-6, eotaxin, MIP-2, and sTNFR1, there were small but significant reductions of these outcome indicators in IL-1RI(-/-) versus IL-1RI(+/+) mice at 6 hours after exposure, but not at other time points, whereas other outcome indicators were unaffected by IL-1RI deficiency. These results suggest that IL-1RI is required for O(3)-induced pulmonary inflammation during subacute O(3) exposure, but plays a more minor role during acute O(3) exposure. In addition, these results suggest that the induction of IL-6 via IL-1RI may be important in mediating the effects of O(3) during subacute exposure.

Neuropeptide Y regulates catecholamine release evoked by interleukin-1beta in mouse chromaffin cells

Activation of the hypothalamic-pituitary-adrenal gland (HPA) axis can modulate the immune system. Cytokines and neuropeptide Y (NPY) are potent regulators of the HPA axis and are both produced by the adrenal medulla. The cytokine interleukin-1beta (IL-1beta) belongs to the interleukin-1 family along with interleukin-1alpha and the interleukin receptor antagonist (IL-1ra). The aim of the present study was to determine the interaction between NPY and IL-1beta in catecholamine (norepinephrine, NE and epinephrine, EP) release from mouse chromaffin cells in culture. We found that IL-1beta increased the constitutive release of NPY, NE and EP from mouse chromaffin cells. This IL-1beta stimulatory effect was blocked by IL-1ra. The immunoneutralization of NPY and the use of the NPY Y(1) receptor antagonist (BIBP 3226) inhibited the stimulatory effect of IL-1beta on catecholamine release from these cells. The present work shows that IL-1beta induces catecholamine release, and in turn this peptide will induce an additional increase in catecholamine release acting through the Y(1) receptor. This work suggests that NPY is involved in the regulatory loop between the immune and the adrenal system in some pathophysiological conditions where plasmatic IL-1beta increases, like in sepsis, rheumatoid arthritis, stress or hypertension.

Activation of the hypothalamic-pituitary-adrenal axis and autonomic nervous system during inflammation and altered programming of the neuroendocrine-immune axis during fetal and neonatal development: lessons learned from the model inflammagen, lipopolysaccharide

The hypothalamic-pituitary-adrenal axis (HPAA) and autonomic nervous system (ANS) are both activated during inflammation as an elaborate multi-directional communication pathway designed to restore homeostasis, in part, by regulating the inflammatory and subsequent immune response. During fetal and neonatal development programming of the HPAA, ANS and possibly the immune system is influenced by signals from the surrounding environment, as part of an adaptive mechanism to enhance the survival of the offspring. It is currently hypothesized that if this programming is either misguided, or the individual's environment is drastically altered such that neuroendocrine programming becomes maladaptive, it may contribute to the pathogenesis of certain diseases. Current research, suggests that exposure to inflammatory signals during critical windows of early life development may influence the programming of various genes within the neuroendocrine-immune axis. This review will provide, (1) an overview of the HPAA and ANS pathways that are activated during inflammation, highlighting studies that have used lipopolysaccharide as a model inflammagen and, (2) evidence to support the hypothesis that inflammatory stress during fetal and neonatal development can alter programming of the neuroendocrine-immune axis, influencing stress and immune responsiveness, and possibly disease resistance later in life.