Stimulation of acetylcholine receptors impairs host defence during pneumococcal pneumonia.

The cholinergic nervous system can inhibit the systemic inflammation accompanying sepsis by virtue of a specific action of acetylcholine on alpha7 cholinergic receptors. The current authors sought to determine the effect of nicotine, an alpha7 cholinergic receptor agonist, on the host response to pneumonia caused by Streptococcus pneumoniae. Mice were intranasally infected with S. pneumoniae and treated with nicotine or saline intraperitoneally using a treatment schedule shown to improve host defence against abdominal sepsis. Nicotine treatment was associated with a transiently enhanced growth of S. pneumoniae, as indicated by higher bacterial loads in both lungs and blood at 24 h after infection. At 48 h after infection, bacterial burdens had increased in both treatment groups and differences were no longer present. Remarkably, mice treated with nicotine showed enhanced lung inflammation at 24 h after infection. Moreover, both lung and plasma concentrations of the pro-inflammatory cytokines tumour necrosis factor-alpha and interferon-gamma were higher in nicotine-treated animals at this time-point. Additional studies examining the effect of nicotine on the immediate (4-h) inflammatory response to S. pneumoniae did not reveal an anti-inflammatory effect of nicotine either. The present data suggest that nicotine transiently impairs host defence in pneumococcal pneumonia.

Expression of adenohypophyseal-hormone receptors in a murine folliculo-stellate cell line.

Adenohypophyseal-hormone production is regulated by hypothalamic peptides and target-gland hormones. Additionally, paracrine regulation by folliculo-stellate cells within the pituitary has been suggested. We recently showed TSH receptor expression in human folliculo-stellate cells and speculated that receptors for other adenohypophyseal hormones might also be expressed by folliculo-stellate cells. Using RT-PCR, we evaluated the expression of receptors for TSH, GH, ACTH, LH, FSH and PRL in a murine folliculo-stellate cell line, TtT/GF. Transcripts of TSH receptor, GH receptor and ACTH receptor were detected in this cell line. LH receptor, FSH receptor and PRL receptor expression, however, could not be demonstrated. We conclude that the TtT/GF cells express some, but not all, receptors for anterior pituitary hormones. This indicates that folliculo-stellate cells might act as mediators in the paracrine regulation of at least some of the hormones secreted by the anterior pituitary.