Bisindolylmaleimide Protein-Kinase-C Inhibitors Delay the Decline in DNA Synthesis in Mouse Hair Follicle Organ Cultures

Abstract

We have used a series of bisindolylmaleimide selective pro-tein-kinase C (PKC) inhibitors to investigate the role of this enzyme in the regulation of cell proliferation in mouse hair follicle organ cultures. Mouse whisker follicles were isolated by microdissection, and rates of DNA synthesis during culture were determined from ³H-thymidine incorporation. The bis-indolylmaleimides Ro 31-7549, Ro 31-8161, Ro 31-8425 and Ro 31-8830 inhibit isolated brain PKC with IC₅₀ values of 8-80 nM, are > 60-fold less potent against protein kinase A, and inhibit PKC-mediated protein phosphorylation in platelets with IC₅₀ values in the range 0.25-4.4 μM. These PKC inhibitors were found to increase levels of mouse hair follicle DNA synthesis, with EC₅₀ values in the range 1-4 μM and maximal levels in the range 151-197% of control. Ro 31-7549 had an IC₅₀ value 50-fold lower than that of minoxidil, while the maximal level of DNA synthesis for the PKC inhibitor was 86% higher. Incubation of mouse hair follicles with Ro 31-7549 resulted in a delay of approximately 24 h in the onset of decline in follicular DNA synthesis rates. Ro 31-6045 and Ro 31-7208, bisindolylmaleimides without activity in the platelet PKC assay, did not affect mouse hair follicle DNA synthesis rates. Taken together, these findings show that PKC mediates, at least in part, the rapid loss of proliferative activity that occurs in mouse whisker follicles in culture, and provide further evidence that PKC plays a role as a negative proliferative signal in hair follicles.

Several Selective Protein Kinase C Inhibitors Including Procyanidins Promote Hair Growth

“…Xiong and Harmon [13] reported that TPA elicits an increase in IL-1ß production, which is a potent inhibitor of hair follicle growth, from dermal papillae. Har- Takahashi/Kamimura/Shirai/Yokoo mon et al [14] reported that bisindolylmaleimides, which are selective PKC inhibitors, delay the decline in mouse whisker follicle growth and concluded that this effect is caused by decreased IL-1ß production from dermal papillae rather than via a direct effect on hair epithelial cells [13]. We suggest in this report that selective PKC inhibitors directly affect hair epithelial cells and promote hair epithelial cell growth.…”

“…Xiong and Harmon [13] reported that TPA induces expression of IL-1ß, a potent inhibitor of hair follicle growth, in dermal papillae. It is reported that selective PKC inhibitors delay the decline of mouse whisker follicle growth in organ culture [14], in proportion to the decrease in IL-1ß production from dermal papillae [13]. However, it has not been elucidated whether PKC inhibitors directly affect hair epithelial cells.…”

Cyclosporin A Promotes Hair Epithelial Cell Proliferation and Modulates Protein Kinase C Expression and Translocation in Hair Epithelial Cells

“…It has been reported that PKC acts as a negative hair-growing factor (Harmon et al, 1995(Harmon et al, , 1997Xiong and Harmon, 1997). Li et al examined the levels of PKC-a and PKC-d in BALB/c mice back skin in the course of hair growth induced by diphencyprone (Li et al, 1999a) and hair plucking (Li et al, 1999b), and concluded that the downregulation of PKC-a expression in skin appears to cause anagen induction in the hair cycle progression.…”

Learning from nudity: lessons from the nude phenotype

“…PKC activation) is upregulated in mouse primary keratinocytes that lack functional Foxn1, overexpression of Foxn1 results in suppression of PKC activation and inhibition of keratinocyte differentiation (58). PKC, an important component of various intracellular signaling pathways, is not only involved in the regulation of keratinocyte proliferation and differentiation, but is also known to inhibit human hair growth in vitro (59–62).…”

“…An additional scenario may involve PKC, whose activity is suppressed by CsA (90). Since Foxn1 may act as a negative regulator of PKC activity (47) and since PKC inhibitors such as procyanidins promote hair growth (60,61), it is conceivable that CsA substitutes for PKC downregulation by Foxn1. If confirmed, this would lend further credence to the concept that PKC activity is a particularly important regulatory target for the Foxn1 transcription factor.…”