Justyna Niderla

Transplants of rat chondrocytes evoke strong humoral response against chondrocyte-associated antigen in rabbits.

Rat chondrocytes transplanted intramuscularly in rabbits produced cartilage. In 1-day-old transplants chondrocytes remained viable. After 1 week peripheral chondrocytes of the transplant were dead and the cartilage was surrounded and resorbed by macrophages. In 2-week-old transplants cartilage deteriorated and was invaded by fibroblast-like cells and macrophages. Sera of rabbits that received two or three consecutive transplants of rat chondrocytes with 2-week intervals contained high titer of antichondrocyte cytotoxic antibodies. A part of the cytotoxic activity could be removed by absorption with rat splenocytes. Western blot analysis of lysates from fresh or 24-h cultured chondrocytes with absorbed sera detected antigen with Mr of ~74 and ~23 kDa. Only the latter remained after reduction in 2-mercaptoethanol. In lysates of fibroblasts and endotheliocytes the 23-kDa antigen was not found but the serum reacted with Mr 39-kDa antigen. In lysates of thymocytes a weak band corresponding to Mr of 35 kDa was present. Serum from rabbits receiving transplants of living chondrocytes followed by chondrocytes suspended in complete Freunds adjuvant contained antibodies directed against components of crude collagenase used for cell isolation. Such antibodies could not be detected in sera of rabbits receiving transplants of living chondrocytes only. Molecular weight of detected antigen differs from that of collagen type II, core of aggrecan, link proteins, and several other macromolecules of cartilage matrix. It could represent either a component of chondrocyte membrane or a membrane-bound substance resistant to enzymes used for isolation. Availability of antibodies against presumably chondrocyte-specific antigen produced during transplant rejection may help to characterize it more precisely and to ascertain whether its presence may influence results of autogenous chondrocyte transplants in humans.

Fluvastatin increases tyrosinase synthesis induced by α-melanocyte-stimulating hormone in B16F10 melanoma cells

The aim of this study was to evaluate the effect of fluvastatin on the alpha-melanocyte-stimulating hormone-mediated increase in tyrosinase activity in the melanoma B16F10 cell line and to establish whether Akt and extracellular signal-regulated kinase (Erk) inhibition is involved in tyrosinase synthesis after fluvastatin administration. Fluvastatin modulates alpha-melanocyte-stimulating hormone induced melanogenesis by increasing tyrosinase mRNA production, as shown by real time PCR, or tyrosinase protein synthesis, as presented by western blot technique. The stimulatory effect of fluvastatin on melanogenesis was, in part, induced by modulation of cell proliferation (decreased melanoma cell proliferation in G2/M phase) and possibly decrease of Akt. These findings indicate that fluvastatin increases tyrosinase synthesis induced by alpha-melanocyte-stimulating hormone in B16F10 cells and reveal an unknown effect of statin use: their influence on melanin production.

Fluvastatin increases tyrosinase synthesis induced by UVB irradiation of B16F10 melanoma cells.

Statins are widely used to lower plasma concentrations of lipids, e.g. cholesterol. One of the main effects of statin treatment is inhibition of hydroxymethyl glutaryl-coenzyme A reductase. The role of fluvastatin, a frequently used statin, was examined in potential modulation of tyrosinase (key enzyme of melanogenesis) synthesis. Levels of tyrosinase mRNA induced by UVB irradiation of B16F10 melanoma cell line were measured by real time PCR. Fluvastatin increases tyrosinase mRNA production induced by UVB irradiation in B16F10 melanoma cell line. Fluvastatin treatment may potentially influence melanin synthesis and protection against UV irradiation.