Interleukin 1 interacts synergistically with forskolin and isobutylmethylxanthine in stimulating bone resorption in organ culture

Flavonoids alter bone-remodelling in auditory ossicle organ cultures

The beneficial role of bioflavonoids in an otosclerosis-like bone-remodelling process can be implicated from its interference with bone resorption induced by prostaglandin E2 (PGE2) in cultured guinea pig ossicles. Ipriflavone (7-isopropoxy-isoflavon) and quercetin reduced PGE2-elevated collagenase-like peptidase (Cl-peptidase) activity and potentiated a PGE2-induced decrease in collagen synthesis. The fact that PGE2 effects are mediated through cyclic AMP in bone turnover and flavonoids act synergistically with PGE2 in collagen synthesis confirm a cyclic AMP phosphodiesterase inhibitory role of flavonoids. It has already been attempted to use Ipriflavone medical treatment of otosclerosis. Quercetin, which has a better than Ipriflavone water-solubility seems as promising as Ipriflavone in the control of the otosclerotic bone-remodelling disturbance.

Pathogenesis of induced rat periapical lesions

Studies of the mechanisms of pathogenesis of periapical lesions were undertaken using a rat model of surgical pulp exposure. In this model, periapical lesions develop rapidly between days 0 and 15 (active phase) and more slowly thereafter (chronic phase). A Gram-negative anaerobic flora, similar to that seen in human beings, are quickly established. Lesions contain a mixed inflammatory cell infiltrate consisting of T cells, neutrophils, B cells, macrophages, and plasma cells. Helper T cells predominate during the active phase, whereas suppressor T cells are more frequent in the chronic phase. Extracts of periapical lesions contain bone-resorbing activity, the highest levels of which are present when lesions are actively expanding. Most bone-resorbing activity is mediated by the cytokine interleukin-1 alpha, as determined by biochemical criteria and antibody neutralization studies. Prostaglandin2 accounts for 10% to 15% of resorptive activity. Cells that express interleukin-1 alpha were identified in pulp beginning on day 2 after exposure and in periapical tissue beginning on day 7, as determined by in situ hybridization and immunostaining. Macrophages, fibroblasts, neutrophils, and osteoclasts were positive for interleukin-1 alpha mRNA and protein. Cells that express tumor necrosis factor alpha were also detected, whereas cells expressing interleukin-1 beta or tumor necrosis factor beta were absent. Finally, periapical bone destruction was inhibited by 60% by treatment with interleukin-1 receptor antagonist. These studies establish a key role for interleukin-1 alpha in the pathogenesis of periapical lesions in the rat model.

Differences in the time course of the effects of oophorectomy in women on parameters of bone metabolism and interleukin-1 levels in the circulation

Interleukin-1 is a cytokine with bone-resorbing activity which is claimed to play a role in the pathogenesis of osteoporosis and of post-oophorectomy bone loss. We measured plasma levels of interleukin-1 (IL-1) in 16 women who underwent hysterectomy and bilateral oophorectomy and in 12 women with hysterectomy alone before surgery and 7, 15, 30, 45 and 60 days after surgery. Only oophorectomized patients showed a significant increase of circulating interleukin-1 levels. This increase was significant only 30 days after surgery, whereas a rise at 7 days (P < 0.001) was observed for serum calcium and hydroxyproline/creatinine and calcium/creatinine ratios. These data do not indicate a definite role of IL-1 in promoting bone resorption in estrogen-deficient women in vivo.