Objective: To investigate the role of protein kinase C (PKC) in the down-regulation of fibroblast proliferation in normal skin (NFb) and hyperplastic scar (SFb) by adrenaline.
Methods: Human NFb and SFb cells were cultured in vitro. Phentolamine (in final concentrations of 0 and 3 x 10(-6) micromol/L) was added to the culture medium. One hour later, adrenaline in different final concentrations (0.00, 0.05, 0.10, 0.20 micromol/L) was added to the culture medium and incubated for 24 hours. The cellular proliferation activity and cell viability rate were determined with MTT. The cell culture supernatant was harvested for the determination of LDH activity to assess the toxicity of phentolamine and adrenaline. The phosph-PKC activity was determined with Western-blotting and was semiquantitatively analyzed.
Results: (1) After stimulation with adrenaline alone, or combined 0.20 micromol/L adrenaline with 3 x 10(-6) micromol/L phentolamine, the cell viability of both NFb and SFb decreased significantly (P < 0.05 or 0.01). (2) There was no difference in the LDH activity between the cells either stimulated by adrenaline in all concentrations or by combination of adrenaline and phentolamine (P > 0.05). (3) The phosphorylation of PKC in NFb and SFb cells stimulated by 0.05, 0.10, 0.20 micromol/L adrenaline was obviously higher than that before stimulation (P < 0.01). When phentolamine in the concentration of 3 x 10(-6) micromol/L was used alone for stimulation, the phosphorylation of PKC in NFb cells (123 +/- 5) was also evidently higher than that before stimulation (80 +/- 5, P < 0.01). But there was no such effect on SFb cells (P > 0.05). When adrenaline in the concentration of 0.05, 0.10 or 0.20 micromol/L was separately added together with phentolamine in the dose of 3 x 10(6) micromol/L for the stimulation, the phosphorylation of PKC in NFb and SFb cells was evidently lower than that when 3 different concentrations of adrenaline was used alone for stimulation (P < 0.01).
Conclusion: Adrenaline can inhibit the proliferation of NFb and SFb by activating PKC through binding alpha adrenaline receptor.