Effects of neuropeptide S on the proliferation of splenic lymphocytes, phagocytosis, and proinflammatory cytokine production of pulmonary alveolar macrophages in the pig

Neuropeptide S (NPS), a newly identified neuropeptide, is involved in many physiological and pathological activities through the NPS receptor (NPSR). Recently, the NPS and NPSR have been detected in peripheral systems of pigs including immune tissues, suggesting that NPS may play an important role in the regulation of immune function. The aim of this study was to demonstrate the presence and function of NPS and NPSR in splenic lymphocytes (SPLs) and pulmonary alveolar macrophages (PAMs) of pigs. By RT-PCR, the expression of NPS and NPSR mRNA was detected in the SPLs and PAMs. NPS immunoreactivity was observed in the membrane and cytoplasm of both SPLs and PAMs. We found that NPS could stimulate the proliferation of SPLs, when NPS was added at concentrations of 0.01, 0.1, 1, 10, 100 and 1000 nM alone or in combination with PHA/LPS in vitro. In macrophages from bronchoalveolar lavage (BAL) fluid of pigs, various doses of NPS (0.01, 0.1, 1, 10, 100 and 1000 nM) up-regulated the phagocytosis of PAMs in comparison to controls. In PAMs, NPS could induce the production of the pro-inflammatory cytokines IL-1β, IL-6 and TNF-α. Taken together, all data suggest that NPS is capable of inducing phagocytosis of non-opsonized E. coli. NPS might act as potent neuroimmunomodulatory factors and affects the maintenance of immune homeostasis.