Induction by cholera toxin of synchronous divisions in vivo in the epidermis resulting in hyperplasia.

Abstract

Intracutaneous injection of cholera toxin, exotoxin of Vibrio cholerae, into the dorsal skin of mice, rats, and hamsters at doses of >0.1 ng evoked an acute reaction at the site of injection, which was characterized histologically by an edematous reaction in the dermis and mitotic stimulation in the epidermis. Mitotic and labeling indices of basal cells of the mouse epidermis showed two peaks at 24 and 48 hr after injection, thereby producing epidermal hyperplasia. The thickness of the interfollicular epidermis increased progressively from 32 hr after toxin injection, being greatest on day 4 and decreasing to normal on day 7. The epidermis on day 4 after injection of 1.0 ng of toxin was about 4-to 6-fold thicker than normal or phosphate buffertreated control skin. This sequence ofevents indicated that cholera toxin induced two successive synchronous divisions of the epidermal cells and produced temporary hyperplasia without interfering with epidermal differentiation. The complete structure and function of the cholera toxin are required for induction of epidermal hyperplasia: no mitotic stimulation was induced by injection ofthe A and B units of the cholera toxin molecule or by preincubation of the toxin with anti-cholera toxin antibody and with the membrane receptor, GM1 ganglioside. Five other agents known to increase the level of intracellular cyclic AMP by different means (dibutyryl cyclic AMP, 3-isobutyl-1-methylxanthine, theophylline, isoproterenol, and prostaglandin El) did not produce a skin reaction.Cholera toxin is a protein exotoxin produced by Vibrio cholerae, which causes diarrhea in cholera patients. The molecular mechanisms of action of cholera toxin have been investigated extensively using intestinal and nonintestinal tissues and are now well understood (1). The toxin molecule has a molecular weight of 84,000 and consists of two types of noncovalently linked subunits, A and B. The pentamer of the B unit binds to the membrane receptor, GM1 ganglioside, and the A unit activates adenylcyclase through mono-ADP ribosylation of GTP-binding protein, thereby increasing the level ofcyclic AMP. This ability is not restricted to intestinal cells but has been found in many mammalian cell types tested, and various biological effects of cholera toxin are probably due to this mechanism.In confirmation of the result of Green (2), during studies on human epidermal cells in culture (3), we found that colonial growth of the cells was markedly enhanced by addition of cholera toxin (unpublished data). This prompted us to examine whether cholera toxin also stimulates growth of epidermal cells in vivo. This paper shows that intracutaneous injection of cholera toxin into the back of mice induced two successive synchronous divisions of basal cells in the epidermis, which resulted in transient hyperplasia without interfering with epidermal differentiation. A preliminary report of this induction of epidermal hyperplasia by cholera toxin was published elsewhere (4).MATERIALS AND METHODS Cholera toxin, its A and B un...

Effects of Cholera Toxin on Delayed‐Type Hypersensitivity to Sheep Red Blood Cells Inoculated Intranasally into Mice

“…CT probably penetrated the lamina propria in the respiratory mucosa, because the intranasal administration of CT evoked an acute reaction, characterized by edematous changes and cellular infiltration of the lamina propria. This edematous reaction, which is probably due to increased permeability of the capillaries in the lamina propria, seems to be similar to that evoked by intracutaneous injection of CT in the mouse skin (2,11). 3) CT in the lamina propria could directly elevate the ability of APC in the respiratory mucosa to present the antigenic determinants to T cells (Figs.…”

2,3,7,8‐Tetrachlorodibenzo‐p‐dioxin: Examination of biochemical effects involved in the proliferation and differentiation of XB cells

“…1 and data not shown). By contrast, TPA, EGF, and cholera toxin are known to produce rapid and large (two to sixfold) increases in epidermal proliferation both in vivo (Kuroki, 1981;Baird et al, 1971;Cohen and Elliot, 1963;Birnham et al, 1976) and in vitro (Yuspa et al, 1976;Rheinwald and Green, 1977;Okada et al, 1982). The effect of TPA, EGF, cholera toxin, and TCDD on 3H-thymidine incorporation in XB/3T3 cultures is shown in Table 1.…”

Cyclic AMP as a mitotic signal for epidermal keratinocytes, but not for dermal fibroblasts.

“…Rozengurt et al (21) reported that cholera toxin induces DNA synthesis in quiescent 3T3 cells synergistically with reduced concentrations of serum (2 to 4 %) and other growth factors. We have reported elsewhere that intracutaneous injections of cholera toxin at doses of more than 0.2 ng stimulate quiescent cells in mouse epidermis and result in epidermal hyperplasia after two successive synchronous divisions (10).…”

“…Our results indicated that cyclic AMP may act as a mitotic signal for epidermal keratinocytes, but not for dermal fibroblasts. This observation led to the in vivo experiments, published elsewhere (10), that showed that cholera toxin induces epidermal hyperplasia after synchronous cell division. …”