Carbonylation induced by antibiotic and pesticide residues on casein increases its IgE binding and allergenicity.

This work aimed to evaluate the effect of carbonylation induced by tetracyclines, ß-lactams, fluoroquinolones, and pyrethroids in caseins of bovine origin on their immunoreactivity and allergenicity. Using a spectrophotometric method, ELISA, dot-blot, and an IgE-mediated milk allergy mouse model, we confirmed that antibiotics and pesticides at their maximum residue limit, promoted the in vitro carbonylation of caseins (among 5.0 ± 0.01 and 67.5 ± 0.70 nmol of carbonyl/mg of protein); furthermore, carbonylations greater than 19 nmol significantly increase the in vitro IgE immunoreactivity of caseins (average OD among 0.63-1.50) regarding the negative control (average OD: 0.56). On the other hand, sensitized mice exposed to oxidized caseins showed increased clinical scores (2-5), positive skin tests, and footpad swelling (0.28-0.59 mm) compared to the negative control (1-2; negative skin tests; 0.1 mm, respectively), denoting increased allergenicity. These results suggest that casein carbonylation increases their IgE immunoreactivity and allergenicity, a fact that could be explained by the resistance to the digestion promoted by carbonylation and by conformational changes in the random coil casein structure, which can expose cryptic epitopes or neoepitopes.

Residues of tetracyclines and ß-lactams antibiotics induce carbonylation of chicken breast.

Background: Worldwide, chicken meat is widely consumed due to its low cost, high nutritional value and non-interference with religious or cultural beliefs. However, during animal husbandry chickens are exposed to many chemical substances, including tetracyclines and ß-lactams, which are used to prevent and cure several infections. Some residues of these compounds may bioaccumulate and be present in chicken meat after slaughtering, promoting oxidative reactions. Methods: In order to evaluate in vitro carbonylation induced by tetracyclines and ß-lactams residues, a proteomic approach was used. For this, chicken muscle was individually contaminated with tetracyclines (tetracycline, chlortetracycline, oxytetracycline, and doxycycline) and ß-lactams (ampicillin, benzathine penicillin, dicloxacillin and oxacillin) at 0.5, 1.0 and 1.5 times their maximum residue level (MRL). Then, sarcoplasmic, myofibrillar and insoluble proteins were extracted and their content were measured using the Bradford method. Protein carbonylation was measured using the 2,4-Dinitrophenylhydrazine alkaline method. Results: Residues of tetracyclines and ß-lactams induced in vitro carbonylation on sarcoplasmic, myofibrillar and insoluble proteins even at 0.5MRL concentrations ( p<0.05). When comparing the carbonylation induced by both antibiotics no differences were found ( p>0.05). Variables such as the partition coefficient (log P) and the concentration of these antibiotics showed a high correlation with the oxidative capacity of tetracyclines and ß-lactams on chicken breast proteins. Conclusions: This study shows that the presence of tetracyclines and ß-lactams residues at MRLs concentrations promotes in vitro carbonylation on chicken breast proteins. Our results provide important insights about the impact of antibiotics on the integrity of meat proteins intended for human consumption.