15-Deoxy-delta12,14-PGJ2, but not troglitazone, modulates IL-1beta effects in human chondrocytes by inhibiting NF-kappaB and AP-1 activation pathways.

The activation of peroxisome proliferator-activated receptor gamma (PPARgamma) has been shown to inhibit the production and the effects of proinflammatory cytokines. Since interleukin-1beta (IL-1beta) directly mediates cartilage degradation in osteoarthritis, we investigated the capability of PPARgamma ligands to modulate IL-1beta effects on human chondrocytes. RT-PCR and Western blot analysis revealed that PPARgamma expression was decreased by IL-1beta. 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2), in contrast to troglitazone, was highly potent to counteract IL-1beta-induced cyclooxygenase-2 and inductible nitric oxide synthase expression, NO production and the decrease in proteoglycan synthesis. Western blot and gel-shift analyses demonstrated that 15d-PGJ2 inhibited NF-kappaB activation, while troglitazone was ineffective. Although 15d-PGJ2 attenuated activator protein-1 binding on the DNA, it potentiated c-jun migration in the nucleus. The absence or the low effect of troglitazone suggests that 15d-PGJ2 action in human chondrocytes is mainly PPARgamma-independent.

Pefloxacin-induced achilles tendon toxicity in rodents: biochemical changes in proteoglycan synthesis and oxidative damage to collagen.

Despite a relatively low incidence of serious side effects, fluoroquinolones and the fluoroquinolone pefloxacin have been reported to occasionally promote tendinopathy that might result in the complication of spontaneous rupture of tendons. In the present study, we investigated in rodents the intrinsic deleterious effect of pefloxacin (400 mg/kg of body weight) on Achilles tendon proteoglycans and collagen. Proteoglycan synthesis was determined by measurement of in vivo and ex vivo radiosulfate incorporation in mice. Collagen oxidative modifications were measured by carbonyl derivative detection by Western blotting. An experimental model of tendinous ischemia (2 h) and reperfusion (3 days) was achieved in rats. Biphasic changes in proteoglycan synthesis were observed after a single administration of pefloxacin, consisting of an early inhibition followed by a repair-like phase. The depletion phase was accompanied by a marked decrease in the endogenous serum sulfate level and a concomitant increase in the level of sulfate excretion in urine. Studies of ex vivo proteoglycan synthesis confirmed the in vivo results that were obtained. The decrease in proteoglycan anabolism seemed to be a direct effect of pefloxacin on tissue metabolism rather than a consequence of the low concentration of sulfate. Pefloxacin treatment for several days induced oxidative damage of type I collagen, with the alterations being identical to those observed in the experimental tendinous ischemia and reperfusion model. Oxidative damage was prevented by coadministration of N-acetylcysteine (150 mg/kg) to the mice. These results provide the first experimental evidence of a pefloxacin-induced oxidative stress in the Achilles tendon that altered proteoglycan anabolism and oxidized collagen.

Proteoglycan and collagen biochemical variations during fluoroquinolone-induced chondrotoxicity in mice.

Although fluoroquinolone antibacterials have a broad therapeutic use, with a relatively low incidence of severe side effects, they have been reported to induce lesions in the cartilage of growing animals by a mechanism that remains unclear. This study was undertaken to determine the potentially deleterious effect of a high dose of pefloxacin (400 mg/kg of body weight) on two main constituents of cartilage in mice, i.e., proteoglycans and collagen. Variations in levels of proteoglycan anabolism measured by in vivo [(35)S]sulfate incorporation into cartilage and oxidative modifications of collagen assessed by detection of carbonyl derivatives were monitored after administration of pefloxacin. Treatment of mice with 1 day of pefloxacin treatment significantly decreased the rate of biosynthesis of proteoglycan for the first 24 h. However, no difference was observed after 48 h. The decrease in proteoglycan synthesis was accompanied by a marked drop in serum sulfate concentration and a concomitant increase in urinary sulfate excretion. The decrease in proteoglycan synthesis, also observed ex vivo, may suggest a direct effect of pefloxacin on this process, rather than it being a consequence of a low concentration of sulfate. On the other hand, treatment with pefloxacin for 10 days induced oxidative damage to collagen. In conclusion, this study demonstrates, for the first time, that pefloxacin administration to mice leads to modifications in the metabolism and integrity of extracellular proteins, such as collagen and proteoglycans, which may account for the side effects observed. These results offer new insights to explain quinolone-induced disorders in growing articular cartilage.

Biotelemetry: an original approach to experimental models of inflammation.

Biotelemetry is a new biological technology which evaluates continuous spontaneous locomotor activity and body temperature in rodents. The telemetry system comprises a transmitter implanted in the peritoneal cavity of the rodent, and a receiver placed beneath the animal's cage. The receiver detects the radio waves and the activity of the rodents as counts which are registered in the computer system, and the adapter detects the calibrated body temperature. First, we showed that biotelemetric studies of different species (rats, guinea pigs, mice and gerbils) provide substantial information about their circadian rhythms. Second, using the most common examples employed in pharmacology of inflammation (hyperthermia, arthritis, ischemia-reperfusion and so on) biotelemetry has helped us to clarify the pathophysiological significance of the parameters of temperature and mobility in several experimental models in rodents.