Perfluorooctanoic acid alters T lymphocyte phenotypes and cytokine expression in mice.

Perfluorooctanoic acid (PFOA) has been used in commercial applications and detected in environmental matrices. This study focuses on whether PFOA affects the function of immune organs (spleen and thymus). Male ICR mice were exposed to 0, 2, 10, 50, and 250 ppm of PFOA in drinking water for 21 days. PFOA differently altered T lymphocyte populations. In the spleen, all doses of PFOA decreased CD8(+) lymphocytes; CD4(+) lymphocytes were increased by 50 and 250 ppm of PFOA. Exposure to 250 ppm of PFOA increased CD8(+) lymphocytes in the thymus. In the histopathological evaluation, the spleen of 250 ppm PFOA-treated groups revealed the increase of lymphoid hyperplasia of white pulp without significant alteration of red pulp. The thymus of 250 ppm PFOA-treated group showed decreased thickness of the cortex and medulla, but lymphoid cells were more densely arranged. PFOA elevated the expression of proinflammatory cytokines (tumor necrosis factor alpha, interleukin-1beta, and interleukin-6) in the spleen, and proto-oncogene, c-myc, in the spleen and thymus. In conclusion, our data demonstrated that PFOA has an immunomodulatory effect by altering T lymphocyte phenotypes and gene expression of proinflammatory cytokines.

Integrity of the cortical actin ring is required for activation of the PI3K/Akt and p38 MAPK signaling pathways in redifferentiation of chondrocytes on chitosan.

Cell shape alterations and accompanying cytoskeletal changes have diverse effects on cell function. We have already shown that dedifferentiated chondrocytes have a round cell morphology and undergo redifferentiation when cultured on chitosan membrane. In the present study, we investigate the role of the cytoskeleton in chondrocyte redifferentiation. Chondrocytes obtained from a micromass culture of chick limb bud mesenchymal cells were subcultured four times. Immunofluorescence analysis of F-actin showed cortical distribution of the actin cytoskeleton upon subculture of dedifferentiated chondrocytes on chitosan membrane. Treatment with cytochalasin D disrupted the cortical actin ring formed during cultivation of chondrocytes on the chitosan membrane, and inhibited chondrocyte redifferentiation. Moreover, cytochalasin D inhibited the phosphorylation of Akt and p38 mitogen activated protein kinase (MAPK), induced during redifferentiation on chitosan membrane. LY294002, an inhibitor of phosphatidylinositol-3-OH-kinase (PI3K), suppressed chondrocyte redifferentiation. These findings suggest that integrity of the actin cytoskeleton is a crucial requirement for PI3K/Akt and p38 MAPK in chondrocyte redifferentiation.

Redifferentiation of dedifferentiated chondrocytes on chitosan membranes and involvement of PKCalpha and P38 MAP kinase.

To investigate the effects of chitosan on the redifferentiation of dedifferentiated chondrocytes, we used chondrocytes obtained from a micromass culture system. Micromass cultures of chick wing bud mesenchymal cells yielded differentiated chondrocytes, but these dedifferentiated during serial monolayer subculture. When the dedifferentiated chondrocytes were cultured on chitosan membranes they regained the phenotype of differentiated chondrocytes. Expression of protein kinase C (PKC) increased during chondrogenesis, decreased during dedifferentiation, and increased again during redifferentiation. Treatment of the cultures with phorbol 12-myristate 13-acetate (PMA) inhibited redifferentiation and down-regulated PKC. In addition, the expression of p38 mitogen-activated protein (MAP) kinase increased during redifferentiation, and its inhibition suppressed redifferentiation. These findings establish a culture system for producing chondrocytes, point to a new role of chitosan in the redifferentiation of dedifferentiated chondrocytes, and show that PKC and p38 MAP kinase activities are required for chondrocyte redifferentiation in this model system.