Amphetamine-induced Fos expression is evident in gamma-aminobutyric acid neurons in the globus pallidus and entopeduncular nucleus in rats treated with intrastriatal c-fos antisense oligodeoxynucleotides

Polymorphonuclear Neutrophils in Osteomyelitis: Link to Osteoclast Generation and Bone Resorption

Chronic and persistent inflammatory processes in bones may lead to severe erosions with consequent functional impairment sometimes requiring amputation of the limb. To explore the relationship between inflammation and bone erosion, biopsies of patients with osteomyelitis due to arterial occlusive disease or to diabetes mellitus were examined (n=31). Histologically, inflammation and bone erosion were confirmed. In the eroded bones the number of osteoclasts correlated with the abundance of infiltrated polymorphonuclear neutrophils (PMN), which were highly activated as shown by expression of MHC class II. For functional characterisation of the infiltrating PMN, patients with implant-associated osteomyelitis, a condition associated with persistent bacterial infection and bone destruction, were recruited. The cells were recovered from infected sites and examined ex vivo. These PMN expressed MHC class II and produced interleukin (IL)-8, a further indication of PMN activation. To assess a possible link between infiltrating PMN and bone erosion, we tested the effect of IL-8 on osteoclast generation in vitro. CD14+ monocytes derived from the peripheral blood of healthy individuals were cultivated with monocyte colony stimulating factor (M-CSF) and IL-8. Within 3 days, a translocation of the transcription factor NFATcl into the nucleus was seen, and by 10 to 20 days multinucleated cells with typical osteoclast morphology appeared that expressed tartrate-resistant acid phosphatase (TRAP) and cathepsin K. Moreover, the cells were able to resorb bone, proving that IL-8 was able to induce the differentiation of monocytes to osteoclasts. Because IL-8 is a major cytokine produced by activated PMN, we propose that in the course of persistent infection infiltrating PMN contribute to induction of osteoclast formation, thus providing a link between inflammation and bone erosion.

Lipopolysaccharide increases gamma-aminobutyric acid synthesis in medial preoptic neurones in association with inhibition of steroid-induced luteinising hormone surge in female rats

Lipopolysaccharide (LPS), an endotoxin produced by gram-negative bacteria, inhibits gonadotrophin secretion and ovulation in female mammals. The present study was undertaken to examine whether gamma-aminobutyric acid (GABA)-synthesising neurones in the medial preoptic area (mPOA) may be involved in the inhibition by LPS of progesterone-induced luteinising hormone (LH) surge in ovariectomised oestrogen-primed rats. An intravenous injection of LPS (10 microg) at noon significantly increased the content of glutamic acid decarboxylase 67 (GAD67), a GABA-synthesising enzyme, in brain tissues including the mPOA. LPS treatment also significantly increased the number of detectable GAD67-immunoreactive (ir) as well as GABA-ir cells in the mPOA, compared to control rats. The same LPS challenge completely eliminated the steroid-induced LH surge, which was normally induced in control rats in the afternoon. A local injection of muscimol (100 ng), a GABA(A) receptor agonist, into the mPOA also significantly attenuated the LH surge, mimicking the effect of LPS. These results suggest that LPS stimulates GABA synthesis in preoptic neurones, which in turn inhibit the LH surge in female rats. The results also support the hypothesis that diminution of the GABAergic suppressive activity in the mPOA permits the LH surge to be induced.