Dexamethasone Modifies the Effect ofPseudomonas aeruginosaExotoxin A on Hearing

Abstract

In the present study, the protective effect of dexamethasone was analysed following exposure of the cochlea to Pseudomonas aeruginosa Exotoxin A (PaExoA). Four groups of albino Sprague-Dawley rats were used. 20 microl saline was instilled through the tympanic membrane into the round window niche (group A, n = 4); 1 microg/20 microl dexamethasone sodium 21-phosphate (dexamethasone) solution was instilled (group B, n = 4); 1 microg/20 microl PaExoA solution was initially instilled followed 1 h later by 20 microl saline (group C, n = 6); and 1 microg/20 microl PaExoA solution was initially instilled followed 1 h later by 1 microg/20 microl dexamethasone solution (group D, n = 6). Frequency-specific (4, 8, 10, 12, 16 and 20 kHz) auditory brainstem responses (ABR) were used to ascertain the threshold prior to exposure and 1, 2, 3, and 5 days and 1 and 2 weeks afterwards. No threshold change was observed in groups A and B, whereas the animals in groups C and D showed some threshold elevation, that in D being smaller than that in C. There was a significant difference at the frequencies 12, 16 and 20 kHz, 2 and 5 days after exposure. The intensity-latency (I-L) curve showed that in group D the cochlear component almost disappeared at high frequency one week after exposure. Our results indicate that dexamethasone can modify the effect of PaExoA caused by non-specific inflammation.

Pseudomonas aeruginosa Exotoxin A-Induced Hepatotoxicity: An Animal Model in Rats

“…The reduction of liver damage was associated with decreased serum levels of ALT, AST and icterus index. Our results were in line with the prevention of PEA-induced ototoxicity by dexamethasone [23]. Moreover, we also demonstrated that combined injection of low-dose PEA and non-toxic dose LPS synergistically caused severe liver damage, characterized by biochemical markers of liver injury.…”

Pseudomonas aeruginosa infection in the hypoventilated middle ear: An experimental model

“…aeruginosa has been used in a number of models for the study of CSOM in chinchillas [9,10], monkeys [11] and guinea pigs [12]. P. aeruginosa exotoxin A has been used in many experimental studies on the pathophysiology and treatment of middle ear infections and its complications [13,14]. The choice of animal depends on biological factors such as anatomical similarities to humans, the physiology of the Eustachian tube and susceptibility to infection, but also on non-scientific factors such as availability and cost.…”

Hearing Loss with Semicircular Canal Transection and Pseudomonas Aeruginosa Otitis Media

“…19 Fortunately, nonspecific anti-inflammatory agents, such as glucocorticoids, may also modulate the damage caused by transection after exotoxin A exposure. 20 One cannot directly extrapolate observations from toxin-mediated models to conditions found in an actual infection. The dose used in the toxin model may have no bearing on the actual exposure to host tissues or the host's response to those toxins over the course of the infection.…”