Neural factors in acute emetic, cardiovascular, and respiratory effects of T-2 toxin in cats

The role of gut microbiota in anorexia induced by T-2 toxin

T-2 toxin is one of trichothecene mycotoxins, which can impair appetite and decrease food intake. However, the specific mechanisms for T-2 toxin-induced anorexia are not fully clarified. Multiple research results had shown that gut microbiota have a significant effect on appetite regulation. Hence, this study purposed to explore the potential interactions of the gut microbiota and appetite regulate factors in anorexia induced by T-2 toxin. The study divided the mice into control group (CG, 0 mg/kg BW T-2 toxin) and T-2 toxin-treated group (TG, 1 mg/kg BW T-2 toxin), which oral gavage for 4 weeks, to construct a subacute T-2 toxin poisoning mouse model. This data proved that T-2 toxin was able to induce an anorexia in mice by increased the contents of gastrointestinal hormones (CCK, GIP, GLP-1 and PYY), neurotransmitters (5-HT and SP), as well as pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α) in serum of mice. T-2 toxin disturbed the composition of gut microbiota, especially, Faecalibaculum and Allobaculum, which was positively correlated with CCK, GLP-1, 5-HT, IL-1β, IL-6 and TNF-α, which played a certain role in regulating host appetite. In conclusion, gut microbiota changes (especially an increase in the abundance of Faecalibaculum and Allobaculum) promote the upregulation of gastrointestinal hormones, neurotransmitters, and pro-inflammatory cytokines, which may be a potential mechanism of T-2 toxin-induced anorexia.

Emetic responses to T-2 toxin, HT-2 toxin and emetine correspond to plasma elevations of peptide YY3-36 and 5-hydroxytryptamine

Trichothecene mycotoxins are a family of potent translational inhibitors that are associated with foodborne outbreaks of human and animal gastroenteritis in which vomiting is a clinical hallmark. Deoxynivalenol (DON, vomitoxin) and other Type B trichothecenes have been previously demonstrated to cause emesis in the mink (Neovison vison), and this response has been directly linked to secretion of both the satiety hormone peptide YY3-36 (PYY3-36) and neurotransmitter 5-hydroxytryptamine (5-HT). Here, we characterized the emetic responses in the mink to T-2 toxin (T-2) and HT-2 toxin (HT-2), two highly toxic Type A trichothecenes that contaminate cereals, and further compared these effects to those of emetine, a natural alkaloid that is used medicinally and also well known to block translation and cause vomiting. Following intraperitoneal (IP) and oral exposure, all three agents caused vomiting with evident dose-dependent increases in both duration and number of emetic events as well as decreases in latency to emesis. T-2 and HT-2 doses causing emesis in 50 % of treated animals (ED50s) were 0.05 and 0.02 mg/kg BW following IP and oral administration, respectively, whereas the ED50s for emetine were 2.0 and 1.0 mg/kg BW for IP and oral exposure, respectively. Importantly, oral administration of all three toxins elicited marked elevations in plasma concentrations of PYY3-36 and 5-HT that corresponded to emesis. Taken together, the results suggest that T-2 and HT-2 were much more potent than emetine and that emesis induction by all three translational inhibitors co-occurred with increases in circulating levels of PYY3-36 and 5-HT.

Mechanisms, causes, investigation and management of vomiting disorders in cats: a literature review

Vomiting is a common presenting complaint in feline practice. This article differs from previous reviews in that it is an evidence-based review of the mechanisms, causes, investigation and management of vomiting in the domestic cat. Published evidence was reviewed, and then used to make recommendations for clinical assessment, diagnosis, antiemetic drug treatment, dietary management and monitoring of cats presenting with vomiting. The strength of the evidence on which recommendations are made (and areas where evidence is lacking for cats) has been highlighted throughout.

Comparison of emetic potencies of the 8-ketotrichothecenes deoxynivalenol, 15-acetyldeoxynivalenol, 3-acetyldeoxynivalenol, fusarenon X, and nivalenol

Although the acute toxic effects of trichothecene mycotoxin deoxynivalenol (DON or vomitoxin), a known cause of human food poisoning, have been well characterized in several animal species, much less is known about closely related 8-ketotrichothecenes that similarly occur in cereal grains colonized by toxigenic fusaria. To address this, we compared potencies of DON, 15-acetyldeoxynivalenol (15-ADON), 3-acetyldeoxynivalenol (3-ADON), fusarenon X (FX), and nivalenol (NIV) in the mink emesis model following intraperitoneal (ip) and oral administration. All five congeners dose-dependently induced emesis by both administration methods. With increasing doses, there were marked decreases in latency to emesis with corresponding increases in emesis duration and number of emetic events. The effective doses resulting in emetic events in 50% of the animals for ip exposure to DON, 15-ADON, 3-ADON, FX, and NIV were 80, 170, 180, 70, and 60 µg/kg bw, respectively, and for oral exposure, they were 30, 40, 290, 30, and 250 µg/kg bw, respectively. The emetic potency of DON determined here was comparable to that reported in analogous studies conducted in pigs and dogs, suggesting that the mink is a suitable small animal model for investigating acute trichothecene toxicity. The use of a mouse pica model, based on the consumption of kaolin, was also evaluated as a possible surrogate for studying emesis but was found unsuitable. From a public health perspective, comparative emetic potency data derived from small animal models such as the mink should be useful for establishing toxic equivalency factors for DON and other trichothecenes.

Deoxynivalenol (vomitoxin)-induced conditioned taste aversions in rats are mediated by the chemosensitive area postrema

The present experiments used a conditioned aversion to a novel saccharin taste to assess the aversive effects of deoxynivalenol (vomitoxin) administration, and to examine the putative mediating role of the chemosensitive area postrema (AP). In experiment 1 adult male rats drank a novel 0.15% saccharin solution followed by injection of deoxynivalenol (n = 7; 0.125 mg/kg, IP) or vehicle (n = 7; propylene glycol, 0.5 ml/kg). In subsequent two-bottle preference tests the rats conditioned with deoxynivalenol displayed significantly (p < 0.01) lower absolute and relative saccharin intake levels in comparison to control rats which exhibited a strong preference for saccharin solution. In experiment 2 adult male rats received area postrema ablations (n = 6) or sham lesions (n = 6). On two conditioning days all rats drank a novel 0.15% saccharin solution followed by injections of deoxynivalenol (0.125 mg/kg, IP). In subsequent two-bottle preference tests the sham-lesioned rats displayed a significant (p < 0.01) aversion to the saccharin stimulus, relative to the area postrema-ablated rats which exhibited a preference for the saccharin solution. Thus, systemic administration of deoxynivalenol, following a novel taste, induced conditioned taste aversions which were mediated by the area postrema.

The efficacy of various classes of anti-emetics in preventing deoxynivalenol-induced vomiting in swine

The Fusarium mycotoxin deoxynivalenol (DON) is a potent emetic agent. While the basic mechanisms which invoke and mediate emesis are still poorly understood, various neurotransmitters appear to be involved. The action of these transmitters can be blocked by various receptor-specific antagonists. The current study investigated the efficacy of several classes of receptor antagonists to block the emetic effect of DON. Following anti-emetic pretreatment, pigs were administered the toxin (i.v., 80 micrograms/kg, or oral, 300 micrograms/kg) and the onset of emesis was monitored. Certain specific serotonin (5HT3)-receptor antagonists (ICS 205-930, BRL 43694 A) were found to efficaciously prevent DON-induced vomiting. These observations support the hypothesis that serotonin plays an important role in chemically induced emesis. Also moderately effective, but requiring high doses, were the 5HT2-receptor antagonists, cyproheptadine and sulpiride. A variety of compounds possessing strong anticholinergic activity were also efficacious. These, however, apparently act directly at the emetic center and thus are capable of preventing emesis regardless of the cause, including chemically induced vomiting. Non-effective were the antihistaminic and antidopaminergic anti-emetics; except, those which also possessed considerable anticholinergic activity, and i.v. administered chlorpromazine which has been speculated to block specific receptors found in the brain's chemoreceptor trigger zone (CTZ) reportedly involved in initiating emesis.

Extravasation of staphylococcal alpha-toxin in normal and injured CNS regions lacking blood-brain barrier function: observations after ventral root replantation

Staphylococcus aureus plays an important role as a bacterial pathogen after traumatic injury. The majority of isolated strains produces alpha-toxin, a 33-kDa protein, with membrane-damaging and lethal effects. The central nervous system (CNS) has been considered as the possible target for the lethal action of this toxin. A transfer of alpha-toxin across an intact blood-brain barrier (BBB) is however unlikely. The aim of the present study was to determine if alpha-toxin is accumulated in CNS regions which lack the BBB function. The distribution of alpha-toxin after intravascular injections, in normal mice and rats as well as in rats subjected to ventral root replantation, was assessed using immunogold technique. The results show that, although alpha-toxin does not cross the BBB, alpha-toxin-like immunoreactivity could be detected in the area postrema and at the optic nerve-retinal junction. Extravasation of alpha-toxin was also shown to occur in the spinal cord even 22 months after ventral root replantation. This finding suggests that axon regeneration after ventral root replantation takes place in a macromolecular environment which is totally different from the normal CNS. The implications of vascular spread of alpha-toxin to regions devoid of BBB function are discussed in relation to the bacterial infections which might complicate severe spinal injuries.

Hypovolemic shock in acute lethal T-2 mycotoxicosis

Experiments were performed on pentobarbital-anesthetized cats to test the hypothesis that hypovolemia rather than cardiac failure is responsible for the acute lethal toxicity of the trichothecene mycotoxin, T-2 toxin (T2T). Measurements were made on mean arterial blood pressure (MAP), arterial pulse pressure (PP), and heart rate (HR) in eight otherwise untreated cats given T2T (2 mg/kg iv) and in three cats similarly injected with T2T but then transfused with plasma and blood. The transfusions to their available extent significantly delayed or counteracted the development of mycotoxic shock (i.e., depressed MAP and PP) and prevented or reversed a rise in the hematocrit. HR remained stable under all conditions. Plasmapheresis followed by whole-blood removal was found best to simulate mechanistically the mycotoxic shock syndrome in six blood donor cats free of T2T. It is concluded that hypovolemia with polycythemia resulting from plasma leakage and internal bleeding accounts for acute lethal T-2 mycotoxicosis.