Heat-Labile Toxin from Enterotoxigenic Escherichia coli Causes Systemic Impairment in Zebrafish Model

Abstract

Heat-labile toxin I (LT-I), produced by strains of enterotoxigenic Escherichia coli (ETEC), causes profuse watery diarrhea in humans. Different in vitro and in vivo models have already elucidated the mechanism of action of this toxin; however, their use does not always allow for more specific studies on how the LT-I toxin acts in systemic tracts and intestinal cell lines. In the present work, zebrafish (Danio rerio) and human intestinal cells (Caco-2) were used as models to study the toxin LT-I. Caco-2 cells were used, in the 62nd passage, at different cell concentrations. LT-I was conjugated to FITC to visualize its transport in cells, as well as microinjected into the caudal vein of zebrafish larvae, in order to investigate its effects on survival, systemic traffic, and morphological formation. The internalization of LT-I was visualized in 3 × 104 Caco-2 cells, being associated with the cell membrane and nucleus. The systemic traffic of LT-I in zebrafish larvae showed its presence in the cardiac cavity, yolk, and regions of the intestine, as demonstrated by cardiac edema (100%), the absence of a swimming bladder (100%), and yolk edema (80%), in addition to growth limitation in the larvae, compared to the control group. There was a reduction in heart rate during the assessment of larval survival kinetics, demonstrating the cardiotoxic effect of LT-I. Thus, in this study, we provide essential new depictions of the features of LT-I.

Bacillus halotolerans attenuates inflammation induced by enterotoxigenic Escherichia coli infection in vivo and in vitro based on its metabolite soyasaponin I regulating the p105-Tpl2-ERK pathway

“…Most importantly, SoSa I reduced the bacterial load of E. coli in the intestinal tract, which is a direct indicator of ETEC infection severity. 1 ETEC infection is known to damage the intestinal mucosa, 45 increase intestinal epithelial cell permeability, 17,46 facilitate bacterial toxin translocation 47 and entry into the circulatory system, 48 and increase serum endotoxin, 49 and d -lactic acid levels, 50 ultimately causing intestinal dysfunction. Our findings indicate that SoSa I effectively lowers endotoxin and d -lactic acid levels, enhances the antioxidant capacity, decreases the expression of intestinal inflammatory factors, and improves intestinal function.…”

Antinociceptive effect of Nephelium lappaceum L. fruit peel and the participation of nitric oxide, opioid receptors, and ATP-sensitive potassium channels

“…2.2 Reversed-phase ultra-high-performance liquid chromatography (RP-UHPLC) coupled to diode array detection (DAD) and mass spectrometry (MS) analysis of ethanol extracts of the fruit peel of Nephelium lappaceum L. maintained apart by sex and reared under standard conditions (28 °C, pH 7, and light/dark cycle of 14/10 h) in individual aquariums (Alesco, Campinas, Brazil) using synthetic brine (60 μg/mL of Instant Ocean sea salts). The experiments were approved by the Butantan Institute Animal Use Ethics Commission (CEUAIB #6438210220) and were conducted in fertilized embryos exposed to E2 medium without or with different EENL concentrations (0.95 and 1.9 μg/mL, or 100 and 200 mg/kg equivalent, respectively), following the protocol of OECD 236: Fish Embryo Acute Toxicity Test and the previous description (Henrique et al, 2021).…”