Regulation of prostaglandin E(2) synthesis in cells derived from chondrocytes of patients with osteoarthritis.

BACKGROUND: Osteoarthritis (OA) is a disorder that causes pain and degeneration of the joint over a chronic time course. Chondrocytes in OA play important roles in maintaining the homeostasis of the joint while they produce many cytokines and pathological mediators, including interleukin-1beta (IL-1beta), cyclooxygenases (COX), and prostaglandin E(2) (PGE(2)). To elucidate the mechanisms of pain due to OA, the pathway of PGE(2) synthesis was analyzed using cells derived from chondrocytes obtained from patients with OA. METHODS: Chondrocytes were isolated from cartilage samples obtained at the time of joint replacement surgery from patients with OA. The chondrocytes at the second passage were cultured with or without IL-1beta, dexamethasone (DEX), or COX inhibitors such as NS-398, meloxicam, and indomethacin. Reverse transcription-polymerase chain reaction and Western blotting analysis were performed to study the levels of mRNA and protein, respectively. An enzyme-linked immunosorbent assay was performed to investigate the translocation of nuclear factor-kappaB (NF-kappaB) to the nucleus, and Western blotting analysis was performed to study the phosphorylation of mitogen-activated protein kinases. RESULTS: IL-1beta markedly enhanced the expression of COX-2 and microsomal prostaglandin E synthase-1 (mPGES-1) at both the mRNA and protein levels. The up-regulation was suppressed by DEX or COX inhibitors. IL-1beta strongly increased the translocation of NF-kappaB to the nucleus and the phosphorylation of extracellular-signal-regulated kinase, p38, and c-Jun amino-terminal kinase; but the up-regulation was not inhibited by DEX or COX inhibitors. Interestingly, in a dose-dependent manner, PGE(2) recovered mPGES-1 expression from suppression by DEX, whereas it did not restore the expression of COX-2 in the presence of DEX and IL-1beta. CONCLUSIONS: These results suggested that in cells derived from OA chondrocytes different mechanisms of regulation exist between mPGES-1 and COX-2, and the expression of mPGES-1 was, at least partially, regulated through the autocrine positive feedback by PGE(2).

Expression of interleukin-1beta, cyclooxygenase-2, and prostaglandin E2 in a rotator cuff tear in rabbits.

We investigated the specific factors related to shoulder pain due to a rotator cuff tear using a model in rabbits. A rotator cuff tear was surgically created, and the expression of interleukin-1beta (IL-1beta), prostaglandin E2 (PGE2), and cyclooxygenase-2 (COX-2) was analyzed. In the supernatant of the tissue culture of the torn tendon, IL-1beta production was detected. The amount of IL-1beta was highest 1 day after injury, and then decreased gradually to 21 days. PGE2, the mediator of pain and the product of COX-2, was also detected in the supernatant of the tissue culture. The production of PGE2 significantly increased to 7 days after injury, and then decreased to 21 days. RT-PCR analysis confirmed the mRNA expression of IL-1beta and COX-2 in the torn tendon. Immunohistochemical study demonstrated that cells in the tendon stump were immunopositive for IL-1beta and COX-2. Furthermore, in the affected joint, articular chondrocytes in the remote area from the tear expressed COX-2 strongly. When the rotator cuff is torn, IL-1beta is produced in the torn tendon, and stimulates the expression of COX-2 in not only the torn tendon but also in articular chondrocytes. The COX-2 then produces PGE2, which would mediate shoulder pain.