Abstract

Background. Cytokines stimulate the expression of the adhesion molecule VCAM-1 in renal tubular epithelial cells. We have recently shown that VCAM-1 can also be upregulated by low molecular weight breakdown products of the matrix constituent hyaluronan (HA) (J Immunol 1998; 161: 3431–3437). The mechanisms of VCAM-1 expression in response to HA remain to be defined.

Methods. Using a defined mouse cortical tubular (MCT) cell line we investigated the effect of protein kinase C (PKC) and tyrosine kinase (TK) inhibition on the HA-stimulated VCAM-1 expression by cell ELISA and RT–PCR or Northern blotting. Furthermore, we examined the effect of PKC and TK inhibition on NF-κB.

Results. We found that the PKC inhibitor GF109203X (acting on conventional, novel and atypical isoforms) inhibited the HA-stimulated VCAM-1 expression in MCT cells dose-dependently up to 90%, whereas chelerythrine (acting on conventional and novel isoforms) had no effect. Downregulation of PKC with PMA did not prevent the HA-stimulated VCAM-1 expression, suggesting that Ca2+- and diacylglycerol-independent (atypical) isoforms of PKC are involved. The TK inhibitor genistein also inhibited the HA-stimulated VCAM-1 expression at the mRNA and protein level up to 70%. Interestingly, the HA-stimulated nuclear translocation of NF-κB could not be prevented with GF109203X and genistein.

Conclusion. These data demonstrate that the HA-stimulated VCAM-1 expression in MCT cells involves PKC and TK pathways. The absence of an effect of PKC and TK inhibitors on the nuclear translocation of NF-κB suggests that additional transcription factors are involved for VCAM-1 expression.

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