Simvastatin inhibits cytokine production and nuclear factor-kB activation in interleukin 1beta-stimulated synoviocytes from rheumatoid arthritis patients.

OBJECTIVES: Recent studies demonstrated in vivo the effectiveness of statins in reducing the inflammatory response in rheumatic diseases, and still more recently, simvastatin has been reported to inhibit in vitro IL-6 and IL-8 production by unstimulated fibroblast-like-synoviocytes (FLS) from rheumatoid arthritis (RA) patients. However, no data are available on the effect of statins on the production of these cytokines induced by IL-1, which plays a crucial role in joint inflammation in the course of active RA in vivo. METHODS: In 12 RA patients, synovial tissue specimens were taken to obtain cultures of FLS. Cultures were incubated with IL-1 +/- simvastatin (5-50 micromol/l), and IL-6 and IL-8 production was evaluated (ELISA), also following the addition of mevalonate and its isoprenoid derivatives. Moreover, nuclear factor-kB (NF-kB) activation (immunocytochemistry and Western Blot analysis) were also evaluated. RESULTS: Culture incubation with IL-1 produced a dramatic increase (up to 40-fold) in cytokine production with respect to unstimulated cells. Simvastatin significantly inhibited (about 20%) IL-6 and IL-8 production from IL-1-stimulated FLS. This effect was completely reverted by the concomitant incubation with mevalonate or geranylgeraniol (but not farnesol or squalene). Moreover, simvastatin produced a clear-cut inhibition of IL-1-induced NF-kB activation. CONCLUSION: Simvastatin significantly inhibits the production of IL-6 and IL-8 also in IL-1-stimulated FLS, even though to a lesser extent than in unstimulated cells, via a HMG-CoA-reductase block with an interference in prenylation process and NF-kB activation. Our results further support the rationale for the use of statins in the treatment of rheumatoid synovitis.

Homocysteine enhances cytokine production in cultured synoviocytes from rheumatoid arthritis patients.

OBJECTIVE: Hyperhomocysteinemia is commonly observed in Rheumatoid Arthritis (RA) patients, thus putatively accounting in part for the high rate of cardiovascular events in these subjects. Homocysteine (Hcy) is known to exert a pro-inflammatory effect putatively contributing to the progression of atherosclerotic lesions by cytokine production from several vascular cell-types. In order to evaluate the possibility that Hcy may play a direct pro-inflammatory activity also in the joints of RA patients, we investigated: (i) the joint concentration of Hcy, and (ii) the effect of Hcy on cytokine production by unstimulated and IL-1beta-stimulated human RA cultured synoviocytes. METHODS: In 5 RA and 5 controls subjects, Hcy was measured in the blood and knee synovial fluid, and specimens of synovial tissue were taken to obtain cell cultures. Cultures were incubated with Hcy (10-100 micromol/l) +/- IL-1beta, and IL-6 and IL-8 concentrations were evaluated in the supernatants (ELISA) together with the activation of nuclear factor-kB (NF-kB) (immunocytochemistry). RESULTS: Hcy was present in synovial fluids, with a mean concentration significantly higher in RA patients than in controls (9.0 +/- 1.1 vs 5.9 +/- 1.2 micromol/l). Hcy enhanced IL-6 and IL-8 production in RA synoviocytes only (up to 35%). Moreover, Hcy produced a clear-cut activation of NF-kB in rheumatoid cells only. CONCLUSION: Hcy enhances IL-1-dependent cytokine production by rheumatoid synoviocytes at a concentration measurable in RA joints in vivo. Thus, in RA patients, Hcy may not only represent an important risk factor for the progression of cardiovascular diseases, but it may also contribute to the joint damage.

Nerve-independence of limb regeneration in larval Xenopus laevis is related to the presence of mitogenic factors in early limb tissues.

Early limbs of larval Xenopus laevis can form a regeneration blastema in the absence of nerves. The nerve-independence could be due to the synthesis of neurotrophic-like factors by the limb bud cells. To test this hypothesis, two series of experiments were performed. Series A: the right hindlimbs of stage 57 larvae (acc. to Nieuwkoop and Faber. 1956. Normal table of Xenopus laevis [Daudin]. Amsterdam: North-Holland Pub. Co.), which are nerve-dependent for regeneration, were amputated through the tarsalia. The regenerating limbs were submitted to: sham denervation; denervation; denervation and implantation of a fragment of an early limb, or a late limb, or a spinal cord. Series B: froglets were subjected to amputation of both forelimbs. The cone blastemas were transplanted into denervated hindlimbs of stage 57 larvae, together with a fragment of an early or a late limb. The results in series A showed that the implantation of early limb tissue into the denervated blastema maintained cell proliferation at levels similar to those observed after the implantation of a spinal cord fragment or in sham denervated blastemas. However, the implantation of late limb tissues were ineffective. The results of series B showed that the implantation of early limb tissue, but not of late limb tissue prevented the inhibition of cell proliferation and the regression of denervated limb blastemas of juveniles. These results indicate that the nerve-independence is related to the synthesis of diffusible mitogenic neurotrophic-like factors in early limb tissues, and that nerve-dependence is established when differentiated cells of late limb tissues stop producing these factors.