The Shiga toxin 2 B subunit inhibits net fluid absorption in human colon and elicits fluid accumulation in rat colon loops

Abstract

Shiga toxin (Stx)-producing Escherichia coli (STEC) colonizes the large intestine causing a spectrum of disorders, including watery diarrhea, bloody diarrhea (hemorrhagic colitis), and hemolytic-uremic syndrome. It is estimated that hemolytic-uremic syndrome is the most common cause of acute renal failure in infants in Argentina. Stx is a multimeric toxin composed of one A subunit and five B subunits. In this study we demonstrate that the Stx2 B subunit inhibits the water absorption (Jw) across the human and rat colonic mucosa without altering the electrical parameters measured as transepithelial potential difference and short circuit current. The time-course Jw inhibition by 400 ng/ml purified Stx2 B subunit was similar to that obtained using 12 ng/ml Stx2 holotoxin suggesting that both, A and B subunits of Stx2 contributed to inhibit the Jw. Moreover, non-hemorrhagic fluid accumulation was observed in rat colon loops after 16 h of treatment with 3 and 30 ng/ml Stx2 B subunit. These changes indicate that Stx2 B subunit induces fluid accumulation independently of A subunit activity by altering the usual balance of intestinal absorption and secretion toward net secretion. In conclusion, our results suggest that the Stx2 B subunit, which is non-toxic for Vero cells, may contribute to the watery diarrhea observed in STEC infection. Further studies will be necessary to determine whether the toxicity of Stx2 B subunit may have pathogenic consequences when it is used as a component in an acellular STEC vaccine or as a vector in cancer vaccines.

Inhibition of Water Absorption and Selective Damage to Human Colonic Mucosa Are Induced by Subtilase Cytotoxin Produced by Escherichia coli O113:H21

“…The resulting diarrhea is an imbalance of absorption and secretion of ions and solutes, followed by the movement of water in an attempt to restore the appropriate ion concentrations (20). The present study provides evidence that SubAB was ineffective in modifying the Isc, as we have previously observed with Stx2 (13). These data are consistent with the hypothesis that an electrogenically silent ionic transport coupled to water absorption may be affected by the SubAB treatment.…”

“…A previous report has shown that Stx2 induces a significant inhibition of absorptive water transport across human colon concomitant with morphological damage in colonic surface cells, including an inflammatory response (13). Here, we report that SubAB also inhibits water absorption and causes histological damage in human colon independent of the presence of Stx2.…”

An Orally Applicable Shiga Toxin Neutralizer Functions in the Intestine To Inhibit the Intracellular Transport of the Toxin

“…HBT inhibits the RNA N-glycosidase activity of the Stx1 A subunit and then interferes with protein synthesis inhibition, suggesting that the direct target of HBT is the catalytic A subunit of Stx. On the other hand, the Stx2 B subunit has been shown to induce fluid accumulation independently of A subunit activity in rat colon loops by altering the balance of intestinal absorption and secretion toward net secretion (4). Thus, the potent inhibitory effect of Ac-PPP-tet on Stx2-induced fluid accumulation in rabbit ileal loops may be attributable to the unique ability of Ac-PPP-tet to inhibit not only the cytotoxicity of the A subunit by inducing aberrant transport and degradation, but also A subunit-independent intracellular signaling activated by the B subunit through binding with Gb3.…”

Immunization with a Chimera Consisting of the B Subunit of Shiga Toxin Type 2 and Brucella Lumazine Synthase Confers Total Protection against Shiga Toxins in Mice

“…BLS and Stx2B were expressed and purified, as previously described (26,27). Briefly, BLS was purified in a Mono-Q column in an HPLC apparatus using a linear gradient of NaCl between 0 and 1 M in 50 mM Tris (pH 8.5) buffer.…”