Gm. Calderon et al., EFFECTS OF TOXIN-A FROM CLOSTRIDIUM-DIFFICILE ON MAST-CELL ACTIVATIONAND SURVIVAL, Infection and immunity, 66(6), 1998, pp. 2755-2761
Toxins A and B from Clostridium difficile are the main cause of antibi
otic-associated diarrhea and pseudomembranous colitis. They cause flui
d accumulation, necrosis, and a strong inflammatory response when inoc
ulated in intestinal loops. Since mast cells are a rich source of infl
ammatory mediators, abundant in the gut, and known to be involved in C
. difficile-induced enteritis, we studied the in vitro effect of toxin
A on isolated mast cells, Normal rats sensitized by infection with Ni
ppostrongilus brasiliensis were used to isolate peritoneal mast cells
(PMC). PMC from naive rats were stimulated with calcium ionophore A231
87 as a model of antigen-independent activation, and PMC from sensitiz
ed rats were stimulated with N. brasiliensis antigens to study immunog
lobulin E-dependent mast cell activation. After 4 h, toxin A did not i
nduce release of nitric oxide or histamine in naive PMC. However, 10 n
g of toxin per mi caused a significant release of tumor necrosis facto
r alpha (TNF-alpha). In contrast, 1 mu g of toxin per mi inhibited ant
igen or A23187-induced histamine release by PMC. Toxin A at 1 mu g/ml
for 4 h caused disruption of actin which aggregated in the cytoplasm a
nd around the nucleus. After 24 h, chromatin condensation, cytoplasmic
blebbing, and apoptotic-like vesicles were observed; DNA fragmentatio
n was documented also. These results suggest that mast cells may parti
cipate in the initial inflammatory response to C. difficile infection
by releasing TNF-alpha upon interaction with toxin A. However, longer
exposure to toxin A affects the release of inflammatory mediators, per
haps because of the alteration of the cytoskeleton and induction of ap
optosis. The impaired functions and survival of mast cells by C. diffi
cile toxin A could hamper the capacity of these cells to counteract th
e infection, thus prolonging the pathogenic effects of C. difficile to
xins.