Significance of nitric oxide concentration in plasma and uterine secretes with puerperal endometritis in dairy cows

Clinical and subclinical endometritis in dromedary camels: An overview of definition and clinical presentation, etiopathogenesis, diagnostic biomarkers, and treatment protocols

The current review collected and analyzed research on clinical endometritis (CE) and subclinical endometritis (SCE) in dromedary camels in terms of definition and clinical presentation, etiopathogenesis, diagnostic biomarkers, and treatment protocols. CE is characterized by uterine inflammation with abnormal vaginal discharges, while SCE comprises uterine inflammation with no clinical signs and is described as the infiltration of polymorphnuclear cells into the endometrium. CE is the prevalent clinical finding of barren female dromedaries (18-60 %). SCE has been detected in 9.9 % of infertile female dromedaries. CE and SCE are observed mainly in repeat breeding females. Unhygienic reproductive management, unsanitary dealings during parturition, and postpartum problems are major risk factors. Environmental stress, immunodeficiency, mucus abrasion, or the presence of other opportunistic microbes are predisposing factors. Trueperella pyogenes, Escherichia coli, Pseudomonas aeruginosa, Streptococcus spp., and Staphylococcus spp. are the major uterine isolates obtained from females with CE, while Bacillus spp., Staphylococcus spp., and Candida albicans are the most frequent isolates of SCE. CE and SCE reveal biomarker changes that could aid in the diagnosis of this common reproductive disorder. Only a few treatment protocols for CE and SCE have been tried and proven to work in camel practice. However, there is room for the new, challenging treatment programs proposed in this review. This review also provides a compilation that may be of use to future research and to those working in the field of camel reproduction.

Relationship between Oxidative Stress and Endometritis: Exploiting Knowledge Gained in Mares and Cows

The etiopathogenesis of endometritis in mares and cows differs significantly; this could depend on a different sensitivity and reactivity of the uterus but also on endocrine and rearing factors and different stress sources. In both species, microorganisms and the immune system play a primary role in the generation of this pathology. Microbiological and cytological tests support clinical examination and significantly improve diagnostic accuracy. For both species, during the inflammation, immune cells invade the endometrium and release bioactive substances to contrast primary or secondary pathogen contamination. These molecules are traceable to cytokines, chemokines, and prostaglandins as well as reactive oxygen and nitrogen species (ROS and RNS), collectively known as RONS. The RONS-mediated oxidation causes morphological and functional alterations of macromolecules, such as proteins, lipids, and nucleic acids, with the consequent production of derivative compounds capable of playing harmful effects. These bioactive molecules and by-products, which have recently become increasingly popular as diagnostic biomarkers, enter the bloodstream, influencing the functionality of organs and tissues. This review has collected and compared information obtained in cows and mares related to the diagnostic potential of these biomarkers that are assessed by using different methods in samples from either blood plasma or uterine fluid.

Evaluation of in vitro Activation of Bovine Endometrial and Vaginal Epithelial and Blood Mononuclear Cells to Produce Nitric Oxide in Response to Mycoplasma bovis, Mycoplasma bovigenitalium and Ureaplasma diversum

Genital mycoplasmosis is a condition present in bovine production systems, and the most important agents involved are Mycoplasma bovis, Mycoplasma bovigenitalium and Ureaplasma diversum. Some aspects of their pathogenesis remain unclear. This study was designed in order to evaluate their ability to stimulate mononuclear cells from the endometrium, vagina and peripheral blood of cycling and healthy cows to produce nitric oxide (NO). Cellular cultures of endometrial, vaginal and peripheral blood cells from 33 healthy cows were cultivated with Mycoplasma bovis, Mycoplasma bovigenitalium and Ureaplasma diversum originated from the 4th passage in culture broth and the NO production was measured by the Greiss reaction. Confirmation of the presence of mononuclear cells and of the agents during and after the NO assay was done by Giemsa stained smears and further cultivation and detection by PCR reaction. Mononuclear cells from all samples produced NO. Mycoplasma bovigenitalium stimulated higher NO production than the others (p<0.05). Endometrial cells produced less NO than vaginal or blood cultured cells. In conclusion, it seems that Mycoplasma bovis, Mycoplasma bovigenitalium, and Ureaplasma diversum are able to activate mononuclear cells and induce the production of NO, thus suggesting that this pathway is elicited in response to the primary infection by these agents. More studies are necessary to verify why these agents remain in the bovine reproductive tract for long periods and how they reassume deleterious effects.

Characterization of immunological, biochemical and inflammatory response of clinical and subclinical endometritis in ewes in the subtropics

Pluriparus Ossimi (n = 50) ewes were used to investigate the immune profile of the affected ewes to accurately diagnose clinical and subclinical endometritis and associations with biochemical variables. Ewes were slaughtered and animals were classified into control (no fertility problems), subclinical endometritis (SCE) and clinical endometritis (CE) groups based on pre-slaughter determinations of conception failure. Serum was collected from ewes to estimate concentrations of pro-inflammatory cytokines including interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and interleukin-8 (IL-8) as well as nitric oxide (NO) concentration. The results from immunological evaluations indicated there were greater (P < 0.001) serum concentrations of IL-6, IL-8, TNF-α and NO in ewes classified with SCE and CE as compared to ewes of the control group. Furthermore, values for concentrations of TNF-α were positively correlated with IL-6 and IL-8 concentrations in ewes of the SCE and CE groups. In ewes classified with CE and SCE there were greater (P < 0.01) concentrations of blood glucose, ALT, AST, urea and creatinine than in ewes of the control group. It is concluded that serum pro-inflammatory cytokines IL-6, IL-8, and TNF-α are diagnostic markers for CE and SCE in ewes and serve as a criterion for different inflammatory complications in ewes classified as having CE or SCE.

Prostaglandin E2 promotes nitric oxide synthase 2, platelet-activating factor receptor, and matrix metalloproteinase-2 expression in Escherichia coli-challenged ex vivo endometrial explants via the prostaglandin E2 receptor 4/protein kinase a signaling pathway

Prostaglandin E₂ (PGE₂) is an inflammatory mediator involved in the pathogenesis of several chronic inflammatory conditions, including endometritis. Previous studies have shown that PGE₂ accumulates in Escherichia coli-challenged ex vivo endometrial explants, increasing the expression of pro-inflammatory factors and aggravating tissue damage; these alterations are linked to key enzymes involved in the synthesis of PGE₂, including cyclooxygenases-2 (COX-2) and microsomal PGES-1 (mPGES-1). In this study, we aimed to investigate whether administration of PGE₂ modulated the activities of nitric oxide synthase 2 (NOS2), platelet-activating factor receptor (PAFR), and matrix metalloproteinase (MMP)-2 in E. coli-challenged ex vivo bovine endometrial explants. Our findings showed that COX-2 and mPGES-1 inhibitors significantly reduced NOS2, PAFR, and MMP-2 expression in the E. coli-challenged ex vivo endometrial explants. In addition, NOS2, PAFR, and MMP-2 expression levels were strongly increased in response to treatment with 15-prostaglandin dehydrogenase inhibitors in the E. coli-challenged ex vivo endometrial explants. However, these stimulatory effects could be blocked by PGE₂ receptor 4 (EP4) and protein kinase A (PKA) inhibitors. Overall, these findings show that pathogenic PGE₂ upregulated NOS2, PAFR, and MMP-2 expression, which may enhance inflammatory damage via the EP4/PKA signaling pathway in E. coli-challenged ex vivo endometrial explants.

Effect of Intrauterine Infusion of Momordica Charantia L. on Oxidative Stress and Pregnancy Rate in Infertile Cows

Introduction

The effect of intrauterine administration of Momordica charantia L. (MC) extract on oxidative changes and pregnancy rate in infertile cows was investigated.

Material and Methods

Endometrial smear specimens were taken from 40 cows with fertility problems for cytological examination, and the cows were randomly divided into two groups: group I (n = 20) was subjected to intrauterine administration of 40 mL (0.25 g/mL) of MC extract, group II (n = 20) was subjected to intrauterine administration of 40 mL of pure olive oil. Blood samples were taken starting from the day of administration of MC extract or olive oil (day 0) and then for three weeks at weekly intervals (days 7, 14, 21). Blood serum samples were evaluated for total antioxidant capacity (TAS), total oxidant level (TOS), oxidative stress index (OSI), lipid hydroperoxide (LOOH), and nitric oxide (NO) levels. In addition, on the 14^th day following treatment, two doses of PGF2α were administrated to all cows at 14-day intervals. Following the second PGF2α administration, insemination and GnRH administration was performed at the 60^th h after PGF2α treatment. Smear samples were stained with Giemsa and immunohistochemically to determine cytological changes and inflammatory status.

Results

According to cytological findings, subclinical endometritis was a prevalent disorder in cows with infertility problem (82.5%; 33/40). Additionally, 60.6% (20/33) of the cows with subclinical endometritis had acute inflammation, whereas remaining 13 cows had chronic endometritis. Of the cows with subclinical endometritis, 50% (8/16) and 35% (6/17) became pregnant in group I and II, respectively (P > 0.05). Although the oxidative stress parameters showed similarities between both groups (P > 0.05), there was a significant difference (P < 0.001) between the groups in terms of mean NO and LOOH levels (NO - 31.20 ± 11.38 vs 44.53 ± 11.50 μmol/L and LOOH - 1.22 ± 0.37 vs 1.89 ± 0.36 μmol/L).

Conclusion

The obtained results indicated that MC administration, especially in the presence of active inflammation, may improve the pregnancy rate by positive reduction of oxidative changes.

Role of lipid mediators in the regulation of oxidative stress and inflammatory responses in dairy cattle

Periparturient dairy cows experience an increased incidence and severity of several inflammatory-based diseases such as mastitis and metritis. Factors associated with the physiological adaptation to the onset of lactation can impact the efficiency of the inflammatory response at a time when it is most needed to eliminate infectious pathogens that cause these economically important diseases. Oxidative stress, for example, occurs when there is an imbalance between the production of oxygen radicals during periods of high metabolic demand and the reduced capabilities of the host's antioxidant defenses. The progressive development of oxidative stress in early lactation cows is thought to be a significant underlying factor leading to dysfunctional inflammatory responses. Reactive oxygen species (ROS) are also produced by leukocytes during inflammation resulting in positive feedback loops that can further escalate oxidative stress during the periparturient period. During oxidative stress, ROS can modify polyunsaturated fatty acids (PUFA) associated with cellular membranes, resulting in the biosynthesis of oxidized products called oxylipids. Depending on the PUFA substrate and oxidation pathway, oxylipids have the capacity of either enhancing or resolving inflammation. In mediating their effects, oxylipids can directly or indirectly target sites of ROS production and thus control the degree of oxidative stress. This review discusses the evidence supporting the roles of oxylipids in the regulation of oxidative stress and the subsequent development of uncontrolled inflammatory responses. Further, the utility of some of the oxylipids as oxidative stress markers that can be exploited in developing and monitoring therapies for inflammatory-based diseases in dairy cattle is discussed. Understanding of the link between some oxylipids and the development or resolution of oxidative stress could provide novel therapeutic targets to limit immunopathology, reduce antibiotic usage, and optimize the resolution of inflammatory-based diseases in periparturient dairy cows.

Maternal and non-maternal factors associated with late embryonic and early fetal losses in dairy cows

Defining factors associated with embryonic and/or fetal losses will be helpful in overcoming such problem, either by adjusting conditions or applying therapeutic approaches to high-risk cows. The objective of this study was to investigate the association between a number of maternal and non-maternal factors and the risk of late embryonic (LED) and early fetal death (EFD) in dairy herds. Additionally, we investigated the effect of treating pregnant cows either with GnRH on day 26 post-insemination, or GnRH on day 26 plus CIDR insertion between days 26 and 33 post-insemination, on the risk of LED/EFD. From 3826 pregnancies, diagnosed at day 30 post-insemination, 851 cows lost the pregnancy by day 70 post-insemination. A mixed-effects logistic model was constructed to assess the effect of cow breed, calving difficulty, postpartum problems, lactation number, days in milk, insemination number, actual 305-day milk production, temperature humidity index (THI) at insemination, estrus synchronization protocols, and other factors, on the risk of LED/EFD. Our findings indicated that Holstein X Brown Swiss crossbreed cows had a lower risk for LED/EFD than Holstein cows (P < 0.05). Cows that had postpartum problems, were inseminated for the first time, produced more milk, or were inseminated at THI ≥75, recorded higher risks of LED/EFD (P < 0.05). Calving difficulty, lactation number, and synchronization protocols were not found to be associated with LED/EFD. Moreover, treatment of the pregnant cows with GnRH on day 26 post-insemination plus CIDR insertion between days 26 and 33 post-insemination decreased the risk of LED/EFD. In conclusion, cows that had postpartum problems, were inseminated early postpartum, produced higher milk, and/or were inseminated at high THI, were under higher risk of LED/EFD. Treating such cows with GnRH on day 26 plus CIDR insertion between days 26 and 33 may decrease the possibility of the LED/EFD.

Transcriptional abundance of antioxidant enzymes in endometrium and their circulating levels in Zebu cows with and without uterine infection

Oxidative stress during peripartum period may compromise the uterine immunity. In the present study, we assessed the oxidative stress and antioxidant status during peripartum period and studied their relationship with postpartum uterine infection in dairy cows. Peripheral blood concentrations of total antioxidant capacity (TAC), malondialdehyde (MDA) and nitric oxide (NO) were determined (day -21, -7, on the day of calving and day +7, +21, +35) in normal (n=11), puerperal metritic (n=7) and clinical endometritic (n=6) cows. Endometrial biopsy was performed on the day of calving and expression of CAT, GPx4 and SOD2 genes was studied using qRT-PCR. Puerperal metritic cows had significantly (P<0.05) lower TAC (on day -7, day 0, day +7, +21 & +35), higher MDA (on day -21, -7 & on the day of calving) and NO (on day 0, +7 & day +35) concentrations compared to normal cows. Similarly, clinical endometritic cows had significantly (P<0.05) lower TAC (on day -7, 0, +7 & +21), higher MDA (on day -21, -7, +7 and +35) and NO (on day +7, +21 & +35) concentrations compared to normal cows. The expression of CAT and GPx4 genes was lower (P<0.05) and SOD2 gene was higher (P<0.05) in endometrial tissue of cows that developed uterine infection compared to normal cows. The relationship of peripheral levels of MDA and NO with antioxidant enzymes expression in endometrial tissue was found significant. Receiver operator characteristic analysis revealed that the concentrations of TAC on day -7 to day +35, MDA on day -21 to day +7 and NO on the day of calving to day +35 were highly correlated to the development of postpartum uterine infection in cows. It may be inferred that the low serum TAC level and high level of lipid peroxidation and NO during peripartum period influenced the endometrial expression of anitioxidative genes that compromised the uterine health during postpartum period.

Impact of metritis on the generation of reactive oxygen species by circulating phagocytes and plasma lipopolysaccharide concentration in peripartum dairy cows

This study examined the relationship between postpartum metritis, reactive oxygen species (ROS) generation, and plasma lipopolysaccharide (LPS) concentration in peripartum dairy cows. Blood was collected twice weekly from 2 weeks prepartum through 6 weeks postpartum. Whole blood chemiluminescence (WBCL) was measured using the luminol-enhanced zymosan-stimulated chemiluminescence assay. Cows were examined for uterine health disorders and classified into two groups, healthy (n = 11) and metritis (n = 5). Metritis had a significant effect on WBCL, with cows with metritis having a higher WBCL. Plasma LPS concentrations in cows with metritis were significantly higher than in healthy cows. To examine the effect of LPS on WBCL, blood was sampled in healthy peripartum cows (1 to 2 weeks prepartum, n = 8; 0 to 3 weeks postpartum, n = 11; and 4 to 8 weeks postpartum, n = 8) and incubated with LPS. At 1 endotoxin units/mL of LPS, similar to the plasma LPS concentration in cows with metritis, the WBCL increased in cows at 0 to 3 weeks postpartum. Results indicate that the increase in ROS generation and plasma LPS concentration are associated with metritis, and LPS may be responsible for enhanced ROS generation in early postpartum dairy cows.

Effects of a bacterial lipopolysaccharide on the reproductive functions of rabbit does

Systemic and local infections and inflammations are known to cause infertility in humans and animals. However, the mechanisms by which infection/inflammation induces infertility are only partially known. The objectives of this study were: (i) to provide models of systemic (acute) and local (sub-acute) inflammation by intra-peritoneal injection or intra-cervical deposition of lipopolysaccharide (LPS) in the rabbit and (ii) to assess their effects on uterine tissues and sperm transport in the genital tract of rabbit does. Intra-peritoneal administration of different doses of LPS induced systemic effects such as fever, anorexia and changes in white blood cells (WBC) count. In our study, LPS inoculation (100μg/kg) produced an inflammation-like status that lasted for about 3 days, with minimal distress for the animals. Intra-peritoneal administration of LPS 60h before artificial insemination induced a rapid increase of IL-1β concentrations. The intra-cervical inoculation of LPS did not show any systemic effects, as confirmed by the lack of changes in body temperature, feed intake and WBC count. Histological examination of uterine tissues showed an endometritis-like inflammation status in LPS-treated does, more severe in those inoculated intra-cervically. The number of spermatozoa recovered from uterine horns and oviducts of intra-cervically treated does was less than that retrieved from intra-peritoneally treated animals and controls. These results suggest (i) that sub-acute or acute inflammation may cause infertility by compromising the uterine environment and/or impairing sperm transport and (ii) that the LPS-induced -infection/inflammation experimental model is useful for studying the mechanisms involved in reproductive dysfunctions in the rabbit.

Postpartal subclinical endometritis alters transcriptome profiles in liver and adipose tissue of dairy cows

Transcriptome alterations in liver and adipose tissue of cows with subclinical endometritis (SCE) at 29 d postpartum were evaluated. Bioinformatics analysis was performed using the Dynamic Impact Approach by means of KEGG and DAVID databases. Milk production, blood metabolites (non-esterified fatty acids, magnesium), and disease biomarkers (albumin, aspartate aminotransferase) did not differ greatly between healthy and SCE cows. In liver tissue of cows with SCE, alterations in gene expression revealed an activation of complement and coagulation cascade, steroid hormone biosynthesis, apoptosis, inflammation, oxidative stress, MAPK signaling, and the formation of fibrinogen complex. Bioinformatics analysis also revealed an inhibition of vitamin B3 and B6 metabolism with SCE. In adipose, the most activated pathways by SCE were nicotinate and nicotinamide metabolism, long-chain fatty acid transport, oxidative phosphorylation, inflammation, T cell and B cell receptor signaling, and mTOR signaling. Results indicate that SCE in dairy cattle during early lactation induces molecular alterations in liver and adipose tissue indicative of immune activation and cellular stress.

Relationship of progesterone, bovine pregnancy-associated glycoprotein-1 and nitric oxide with late embryonic and early fetal mortalities in dairy cows

The aim of the present study was to determine the relationship of progesterone (P4), bovine pregnancy-associated glycoprotein-1 (bPAG-1) and nitric oxide (NO) levels with late embryonic (LEM; day 28 to day 42) and early fetal mortalities (EFM; > day 42 to day 56) in dairy cows. Transrectal ultrasonography (6-8 MHz) was performed in 100 Holstein-Friesian cows at days 28, 42 and 56 after artificial insemination (AI; day 0) to diagnose pregnancy and to monitor the fate of the embryo. After ultrasound scanning of each cow, a milk sample was collected for assessment of P4 by an ELISA test and a blood sample was collected for assessment of bPAG-1, by using a double-antibody radioimmunoassay, and serum NO metabolites (nitrate + nitrite). Based on ultrasonographic examinations and bPAG-1-RIA, 41 of 100 inseminated cows were confirmed pregnant at day 28 after AI. Nine cows suffered of LEM, and 6 cows suffered of EFM and the overall pregnancy loss rate was 36.6% (15/41) between days 28 and 56 of pregnancy. By logistic regression analysis, there were no significant relationships between the level of P4 and bPAG-1 at day 28 after AI and the occurrence of LEM and EFM. Also, there were no significant relationships between the levels of P4 and bPAG-1 at day 42 and the occurrence of EFM. On the other hand, a significant relationship (P<0.05) was found between NO level at day 28 and the occurrence of LEM. In conclusion, measurement of the serum NO concentration at day 28 of pregnancy might help to predict the outcome of pregnancy by day 42 in dairy cows but further studies are needed to confirm this.

Peripheral blood leukocytes of cows with subclinical endometritis show an altered cellular composition and gene expression

Subclinical endometritis (SCE) is an important postpartum disease in dairy cows, but conventional cytobrush diagnosis often gives imprecise results. The aim of this study was to analyze disease-associated changes in peripheral blood as potential diagnostic parameters. Cellular subpopulations of blood leukocytes from cows with or without SCE (45-55 days postpartum) were flow-cytometrically quantified. Gene expression of whole blood leukocytes was assessed by PAXgene analysis. Subclinical endometritis cows showed significantly higher number of blood mononuclear cells and neutrophils. Among mononuclear cells, numbers of B-cells, NK-cells, and CD172a-positive monocytes were significantly elevated. Compared with non-SCE cows, blood leukocytes of SCE cows significantly expressed higher copy numbers of CXCL8, TNF, and IL12. To test whether circulating plasma factors are responsible for these changes, leukocytes, polymorphonuclear cells, and monocyte subpopulations (classical, intermediate, nonclassical) of healthy cows were stimulated with plasma of SCE and non-SCE cows. Although gene expression of whole leukocytes and polymorphonuclear cells remained unaltered, plasma from SCE animals significantly elevated expressed messenger RNA copy numbers of CXCL8, CXCL1, and IL1B in intermediate monocytes. In conclusion, elevated number of selected mononuclear subpopulations in peripheral blood and enhanced expression of distinct genes encoding for inflammatory mediators in blood leukocytes reflect the subclinical uterine inflammatory process in cows. Whether the observed changes in the periphery of SCE cows are the consequence of the uterine inflammatory process, or whether they affect the pathogenesis of the disease is currently unknown.

Inflammatory responses to induced infectious endometritis in mares resistant or susceptible to persistent endometritis

Background

The objective of the study was to evaluate the gene expression of inflammatory cytokines (interleukin [IL]-1β, IL-6, IL-8, IL-10, tumor necrosis factor [TNF]-α, IL-1 receptor antagonist [ra] and serum amyloid A (SAA) in endometrial tissue and circulating leukocytes in response to uterine inoculation of 10⁵ colony forming units (CFU) Escherichia coli in mares. Before inoculation, mares were classified as resistant or susceptible to persistent endometritis based on their uterine inflammatory response to infusion of 10⁹ killed spermatozoa and histological assessment of the endometrial quality. Endometrial biopsies were obtained 3, 12, 24 and 72 hours (h) after bacterial inoculation and blood samples were obtained during the 7 day period post bacterial inoculation. Expression levels of cytokines and SAA were determined by quantitative real-time reverse transcriptase PCR (qRT-PCR).

Results

Compared to levels in a control biopsy (obtained in the subsequent estrous), resistant mares showed an up-regulation of IL-1β, IL-6, IL-8 and TNF-α at 3 h after E. coli inoculation, while susceptible mares showed increased gene expression of IL-6 and IL-1ra. Susceptible mares had a significant lower gene expression of TNF-α,IL-6 and increased expression of IL-1ra 3 h after E. coli inoculation compared to resistant mares. Susceptible mares showed a sustained and prolonged inflammatory response with increased gene expression levels of IL-1β, IL-8, IL-1ra and IL-1β:IL-1ra ratio throughout the entire study period (72 h), whereas levels in resistant mares returned to estrous control levels by 12 hours. Endometrial mRNA transcripts of IL-1β and IL-1ra were significantly higher in mares with heavy uterine bacterial growth compared to mares with no/mild growth.

All blood parameters were unaffected by intrauterine E. coli infusion, except for a lower gene expression of IL-10 at 168 h and an increased expression of IL-1ra at 48 h observed in susceptible mares compared to resistant mares.

Conclusions

The current investigation suggests that endometrial mRNA transcripts of pro-inflammatory cytokines in response to endometritis are finely regulated in resistant mares, with initial high expression levels followed by normalization within a short period of time. Susceptible mares had a prolonged expression of pro-inflammatory cytokines, supporting the hypothesis that an unbalanced endometrial gene expression of inflammatory cytokines might play an important role in the pathogenesis of persistent endometritis.