Akira Shimizu

Ehime University, Matuyama, Ehime, Japan

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Publications (3)5.15 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: To assess effects of Celecoxib, selective cyclo-oxygenase (COX)-2 inhibitor, on matrix synthesis by chondrocytes under mechanical stress in vitro. Chondrocytes from 7-day-old rat articular cartilage were cultured. Cyclic mechanical stress (0.5 Hz, 7% elongation) was loaded using a Flexercell strain unit in the presence of Celecoxib, Indomethacin, and Ketoprofen. Concentrations of chondroitin sulfate (CS) in culture media were measured by high-performance liquid chromatography. Nitric oxide (NO) formation was detected by measuring NO2-accumulation in culture supernatants during the Griess reaction, using sodium nitrite as a standard. Levels of mRNA for aggrecan (AGC), type II collagen (CII), COX-2, and membrane-associated prostaglandin E synthase-1 (mPGES-1) were measured using real time reverse transcriptase-polymerase chain reaction. Under mechanical stress, levels of AGC and CII mRNA were decreased, while COX-2 mRNA levels were increased. Of the three drugs tested, only Celecoxib prevented the decrease of AGC mRNA and inhibited the release of CS. In addition, Celecoxib suppresses the level of mPGES-1 mRNA. These findings show that excessive mechanical stress decreases synthesis of matrix components in chondrocytes through a NO-regulated pathway, and suggest that Celecoxib has a protective effect on matrix metabolism.
    International Journal of Molecular Medicine 01/2006; 16(6):1083-8. · 1.96 Impact Factor
  • Foot & Ankle International 12/2005; 26(11):994-6. · 1.47 Impact Factor
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    ABSTRACT: Abstract We examined the effect of interleukin-4 (IL-4) on matrix synthesis in chondrocytes under excessive mechanical stress in vitro. Chondrocytes from 7-day-old rat articular cartilage were incubated in the presence of rat IL-4 (0, 1, and 10 ng/ml) under a 5% CO2 atmosphere for 36 h. Cyclic mechanical stress (0.5 Hz, 7% elongation) was loaded using a Flexercell strain unit for 12, 16, and 24 h. Levels of messenger RNA (mRNA) for aggrecan (AGG), type II collagen (CII), fibronectin (FN), and integrin-β1 (INTb1) were measured by real-time reverse transcriptase polymerase chain reaction (RT-PCR) using GAPDH as the internal control. Mechanical stress for 16 h significantly decreased levels of mRNA for both AGG and CII (P < 0.01), but with rat IL-4 at doses of 1 or 10 ng/ml these levels recovered (P < 0.05). In addition, mRNA levels of FN and INTb1 were increased by IL-4 in chondrocytes under mechanical stress (P < 0.05). IL-4 protects chondrocytes loaded with excessive mechanical stress against degradation.
    Modern Rheumatology 09/2004; 14(4):296-300. · 1.72 Impact Factor