Regulation of leukocyte function-associated antigen 1-mediated adhesion by somatostatin and substance P in mouse spleen cells

Hemokinin-1 and substance P stimulate production of inflammatory cytokines and chemokines in human colonic mucosa via both NK1 and NK2 tachykinin receptors

There is increasing focus on the involvement of tachykinins in immune and inflammatory responses. Hemokinin-1 (HK-1) is a recently identified tachykinin that originates primarily from immune cells, and has structural similarities to substance P (SP), found mainly in neurons. However, there are species differences in HK-1, and the role of HK-1 in humans, particularly the intestine, has received minimal attention. The aim of this study was to investigate the inflammatory role of human HK-1 in the human colon. The effects of HK-1 and SP were compared on the production of multiple inflammatory cytokines and chemokines from human colonic mucosal explants. Data generated by Procarta multiplex assay and QuantiGene assay demonstrated that 4 h incubation with HK-1 (0.1 μM) significantly stimulated transcript expression and release of MCP-1, MIP-1α and β, RANTES, TNF-α, IL-1β and IL-6 from the mucosa. SP (0.1 μM) had comparable actions, but had no effect on MCP-1 or RANTES. These effects were inhibited separately by tachykinin NK₁ and NK₂ receptor antagonists SR140333 and SR48968 (both 0.1 μM), suggesting that these responses were mediated by both NK1 and NK2 receptors. In conclusion, these data support a novel inflammatory role for HK-1 in human colon, signaling via NK1 and NK2 receptors (and possibly other tachykinin-preferring receptors) to regulate the release of a broad spectrum of proinflammatory mediators. The study suggests that along with SP, HK-1 is also a proinflammatory mediator, likely involved in colonic inflammation, including inflammatory bowel disease (IBD).

Stress induced neuroendocrine-immune plasticity: A role for the spleen in peripheral inflammatory disease and inflammaging?

Research over the past decade has revealed close interaction between the nervous and immune systems in regulation of peripheral inflammation linking psychosocial stress with chronic somatic disease and aging. Moreover emerging data suggests that chronic inflammations lead to a pro-inflammatory status underlying premature aging called inflammaging. In this context, the spleen can be seen as a switch board monitoring peripherally derived neuroendocrine-immune mediators in the blood and keeping up a close communication with the central stress response via its mainly sympathetic innervation. The effect aims at balanced and well-timed stress axis activation and immune adaptation in acute peripheral inflammatory events. Constant adjustment to the needs generated by environmental and endogenous challenges is provided by neuroendocrine-immune plasticity. However, maladaptive plasticity induced e.g., by chronic stress-axis activation and excessive non-neuronal derived neuroendocrine mediators may be at the heart of the observed stress sensitivity promote inflammaging under chronic inflammatory conditions. We here review the role of neurotransmitters, neuropeptides and neurotrophins as stress mediators modulating the immune response in the spleen and their potential role in inflammaging.

Role of preprotachykinin-A gene products on multiple organ injury in LPS-induced endotoxemia

Endotoxemia is a life-threatening, inflammatory condition that involves multiple organ injury and dysfunction. Preprotachykinin-A (PPT-A) gene products, substance P (SP), and neurokinin-A have been shown to play an important role in neurogenic inflammation. To investigate the role of PPT-A gene products on multiple organ injury in LPS-induced endotoxemia, endotoxemia was induced by LPS administration (10 mg/kg, i.p.) in PPT-A gene-deficient mice (PPTA(-/-)) and the wild-type (WT) control mice (PPT-A+/+). I.p. administration of LPS to WT mice caused a significant increase in circulating levels of SP as well as in liver, lung, and kidney. PPT-A gene deletion significantly protected against liver, pulmonary, and renal injury following LPS-induced endotoxemia, as evidenced by tissue myeloperoxidase activities, plasma alanine aminotransferase, aspartate aminotransferase levels, and histological examination. Furthermore, PPT-A(-/-) mice had significantly attenuated chemokines, proinflammatory cytokines, and adhesion molecule levels in the liver, lung, and kidney. These results show that PPT-A gene products are critical proinflammatory mediators in endotoxemia and the associated multiple organ injury. In addition, the data suggest that deletion of the PPT-A gene protected mice against organ damage in endotoxemia by disruption in neutrophil recruitment.

An update on somatostatin receptor signaling in native systems and new insights on their pathophysiology

The peptide somatostatin (SRIF) has important physiological effects, mostly inhibitory, which have formed the basis for the clinical use of SRIF compounds. SRIF binding to its 5 guanine nucleotide-binding proteins-coupled receptors leads to the modulation of multiple transduction pathways. However, our current understanding of signaling exerted by receptors endogenously expressed in different cells/tissues reflects a rather complicated picture. On the other hand, the complexity of SRIF receptor signaling in pathologies, including pituitary and nervous system diseases, may be studied not only as alternative intervention points for the modulation of SRIF function but also to exploit new chemical space for drug-like molecules.

Substance P as an Immunomodulatory Neuropeptide in a Mouse Model for Autoimmune Hair Loss (Alopecia Areata)

Alopecia areata (AA) is an autoimmune disorder of the hair follicle characterized by inflammatory cell infiltrates around actively growing (anagen) hair follicles. Substance P (SP) plays a critical role in the cutaneous neuroimmune network and influences immune cell functions through the neurokinin-1 receptor (NK-1R). To better understand the role of SP as an immunomodulatory neuropeptide in AA, we studied its expression and effects on immune cells in a C3H/HeJ mouse model for AA. During early stages of AA development, the number of SP-immunoreactive nerve fibers in skin is increased, compared to non-affected mice. However, during advanced stages of AA, the number of SP-immunoreactive nerves and SP protein levels in skin are decreased, whereas the expression of the SP-degrading enzyme neutral endopeptidase (NEP) is increased, compared to control skin. In AA, NK-1R is expressed on CD8+ lymphocytes and macrophages accumulating around affected hair follicles. Additional SP supply to the skin of AA-affected mice leads to a significant increase of mast cell degranulation and to accelerated hair follicle regression (catagen), accompanied by an increase of CD8+ cells-expressing granzyme B. These data suggest that SP, NEP, and NK-1R serve as important regulators in the molecular signaling network modulating inflammatory response in autoimmune hair loss.

Effect of CP-96,345 on the expression of adhesion molecules in acute pancreatitis in mice

We investigated the effect of a specific neurokinin-1 receptor (NK1R) antagonist, CP-96,345, on the regulation of the expression of adhesion molecules ICAM-1, VCAM-1, E-selectin, and P-selectin as well as leukocyte recruitment during acute pancreatitis (AP). AP was induced in male Balb/C mice by 10 consecutive hourly intraperitoneal injections of caerulein. In the treatment groups, CP-96,345 was administered at 2.5 mg/kg ip either 30 min before or 1 h after the first caerulein injection. Animals were killed, and the lungs and pancreas were isolated for RNA extraction and RT-PCR or for immunohistochemical staining. mRNA expression of the four adhesion molecules was upregulated in the pancreas during AP. Treatment with CP-96,345 effectively reduced the mRNA expression of P-selectin and E-selectin but not ICAM-1 and VCAM-1. In the lung, ICAM-1, E-selectin, and P-selectin mRNA expression increased during AP. Antagonist treatment suppressed this elevation. Similar expression patterns were seen in the immunohistochemical stainings. Intravital microscopy of the pancreatic microcirculation revealed the effect of CP-96,345 on leukocyte recruitment. The present study provides important information on the relationship between NK1R activation and the regulation of adhesion molecules. Also, this study points to the differential regulation of inflammation in the pancreas and lung with AP.

Suppression of autoimmune encephalomyelitis by a neurokinin-1 receptor antagonist — A putative role for substance P in CNS inflammation

Substance P (SP) is an excitatory neurotransmitter in the central and peripheral nervous system. Most of its physiological functions are mediated through binding to the neurokinin-1 receptor (NK-1R). Recently, proinflammatory properties of SP have been described. In this study we utilized T cell transfer experimental autoimmune encephalomyelitis (EAE) to investigate the role of SP in CNS autoimmune disease. Treatment with the NK-1R antagonist CP-96,345 dramatically reduced clinical and histological signs of EAE if administered before disease onset. The protective effect of CP96,345 treatment was related to a reduced expression of the adhesion molecules ICAM-1 and VCAM-1 on CNS endothelia. The cellular composition or activation status of splenocytes was not affected by CP-96,345 administration, while the secretion of proinflammatory Th1 cytokines was reduced in treated animals. Th2 cytokines remained largely unaffected by NK-1 receptor antagonist treatment. In summary, our findings suggest that the protective effect of CP96,345 treatment is mediated by stabilization of the blood-brain barrier and suppression of Th1 immunity.

Memory T cell populations in the lung airways are maintained by continual recruitment

Effector memory T cell populations in the periphery play a key role in cellular immune responses to secondary infections. However, it is unclear how these populations are maintained under steady-state conditions in nonlymphoid peripheral sites, such as the lung airways. In this study, we show that LFA-1 expression is selectively down-regulated following entry of memory T cells into the lung airways. Using Sendai virus as a mouse model of respiratory virus infection, we use LFA-1 expression levels to demonstrate that effector memory T cell populations in the lung airways are maintained by continual recruitment of new cells from the circulation. The rate of memory cell recruitment is surprisingly rapid, resulting in replacement of 90% of the population every 10 days, and is maintained for well over 1 year following viral clearance. These data indicate that peripheral T cell memory is dynamic and depends on a systemic source of T cells.

Somatostatin down-regulates LFA-1 activation by modulating Rap1 expression in CD4+ and CD8+ T cells

Leukocyte function-associated antigen-1 (LFA-1) is one of the integrins that are expressed on the leukocytes, and has been shown to play an important role in leukocyte trafficking. The adhesive activity of LFA-1 is governed partially by the Rap1. This study examined that the relationship between LFA-1 and Rap1 mRNA expressions by anti-CD3 and anti-CD3+SOM treatment in the CD4+ and CD8+ T cells. The LFA-1 mRNA expression levels following the anti-CD3 and anti-CD3+SOM treatment for 30 min was greater on the CD8+ T cells, and the LFA-1 expression of the CD8+ T cells with anti-CD+SOM treatment was affected more severely than that of the CD4+ T cells. The Rap1 mRNA expression patterns following anti-CD3 and anti-CD3+SOM stimulation in the CD4+ and CD8+ T cells were similar to the LFA-1 expression patterns, and the expression level following anti-CD3+SOM treatment was suppressed more significantly in the CD8+ T cells. These results suggest that the difference in the Rap1 expression level after stimulation might explain the differences in the LFA-1 expression level on the T cell subsets, and that the down-regulation of Rap1 expression following SOM treatment is closely related to the diminished LFA-1 expression.

Capillary feeding of specific dsRNA induces silencing of the isac gene in nymphal Ixodes scapularis ticks

Ixodes scapularis transmits several pathogens including Borrelia burgdorferi. Bioactive compounds in tick saliva support tick feeding and influence pathogen transmission to the mammalian host. These studies utilized oral delivery of dsRNA to silence an anticomplement gene (isac) in I. scapularis nymphs. Silencing of isac significantly reduced fed-tick weight compared to delivery of control lacZ dsRNA, and immunoblots specific for FlaB protein indicated a reduction in spirochete load in isac-silenced infected nymphs. SDS-PAGE demonstrated that isac gene silencing affected expression of a number of salivary and non-salivary gland proteins in ticks. Finally, multiple isac cDNA homologues were cloned, and these may represent a new gene family coexpressed during tick feeding. This work presents a novel oral delivery approach for specific gene silencing in I. scapularis nymphs and characterizes the effect of isac on blood-feeding in an attempt to block transmission of B. burgdorferi.