Abstract
High neutrophil (PMN, Polymorphonuclear neutrophil) counts in the endometrium of cows affected by endometritis, suggests the involvement of oxidative stress (OS) among the causes of impaired fertility. Protein oxidation, in particular, advanced oxidation protein products (AOPP), are OS biomarkers linked to PMN activity. To test this hypothesis, the relationship between protein oxidation and uterus health was studied in thirty-eight dairy cows during the puerperium. The animals were found to be cycling, without any signs of disease and pharmacological treatments. PMN count was performed either through a cytobrush or a uterine horn lavage (UHL). Cows were classified into four groups, based on the uterine ultrasonographic characteristics and the PMN percentage in the uterine horns with a higher percentage of high neutrophil horn (HNH). They were classified as: Healthy (H); Subclinical Endometritis (SCE); Grade 1 Endometritis (EM1); and Grade 2 Endometritis (EM2). AOPP and carbonyls were measured in plasma and UHL. UHL samples underwent Western blot analysis to visualize the carbonyl and dityrosine formation. Plasma AOPP were higher (p < 0.05) in EM2. AOPP and carbonyl group concentrations were higher in the HNH samples (p < 0.05). Protein concentration in the UHL was higher in the EM2 (p < 0.05). Carbonyl and dityrosine formation was more intense in EM1 and EM2. Protein oxidation observed in the EM2 suggests the presence of an inflammatory status in the uterus which, if not adequately hindered, could result in low fertility.
Highlights
A considerable percentage of dairy cows experience some form of uterine infection during the postpartum period [1]
Unresolved inflammation can increase the risk of embryonic mortality, and it is conceivable that if potentially pathogenic microorganisms are retained in the uterus for a long time after parturition or are introduced at the time of artificial insemination (AI) [4], a chronic inflammatory reaction may occur and compromise the embryonic development
Neutrophil percentages in the high neutrophil horn (HNH) and the low neutrophil horn (LNH) correlated with those observed in cytobrush technique (CB), and the diagnosis of subclinical endometritis performed by the CB sample evaluation agreed with that performed by the HNH and the LNH sample evaluation, the classification based on the neutrophil percentage observed in the HNH seemed more accurate, as it allowed the identification of the Subclinical Endometritis (SCE) subjects
Summary
A considerable percentage of dairy cows experience some form of uterine infection during the postpartum period [1]. The composition of the uterine microflora changes over time and bacteria are spontaneously cleared [2]. The risk of developing clinical endometritis remains elevated, especially in cows that deliver twins or experience stillbirth, dystocia, retained placenta, or metabolic disorders [1]. The development of subclinical endometritis can negatively impact fertility if not detected and cured in time [1,3]. Several scientific investigations have revealed that changes in the endometrial gene expression could be found in animals affected by subclinical endometritis. Gene expression patterns of embryos obtained from cows affected by subclinical endometritis were different from those observed in healthy cows [3]. Secretions from the inflamed endometrium can affect embryonic development in vitro, leading to a reduction in the blastocyst quality [5]
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