Buffalo sperm surface proteome profiling reveals an intricate relationship between innate immunity and reproduction

Background

Low conception rate (CR) despite insemination with morphologically normal spermatozoa is a common reproductive restraint that limits buffalo productivity. This accounts for a significant loss to the farmers and the dairy industry, especially in agriculture-based economies. The immune-related proteins on the sperm surface are known to regulate fertility by assisting the spermatozoa in their survival and performance in the female reproductive tract (FRT). Regardless of their importance, very few studies have specifically catalogued the buffalo sperm surface proteome. The study was designed to determine the identity of sperm surface proteins and to ascertain if the epididymal expressed beta-defensins (BDs), implicated in male fertility, are translated and applied onto buffalo sperm surface along with other immune-related proteins.

Results

The raw mass spectra data searched against an in-house generated proteome database from UniProt using Comet search engine identified more than 300 proteins on the ejaculated buffalo sperm surface which were bound either by non-covalent (ionic) interactions or by a glycosylphosphatidylinositol (GPI) anchor. The singular enrichment analysis (SEA) revealed that most of these proteins were extracellular with varied binding activities and were involved in either immune or reproductive processes. Flow cytometry using six FITC-labelled lectins confirmed the prediction of glycosylation of these proteins. Several beta-defensins (BDs), the anti-microbial peptides including the BuBD-129 and 126 were also identified amongst other buffalo sperm surface proteins. The presence of these proteins was subsequently confirmed by RT-qPCR, immunofluorescence and in vitro fertilization (IVF) experiments.

Conclusions

The surface of the buffalo spermatozoa is heavily glycosylated because of the epididymal secreted (glyco) proteins like BDs and the GPI-anchored proteins (GPI-APs). The glycosylation pattern of buffalo sperm-surface, however, could be perturbed in the presence of elevated salt concentration or incubation with PI-PLC. The identification of numerous BDs on the sperm surface strengthens our hypothesis that the buffalo BDs (BuBDs) assist the spermatozoa either in their survival or in performance in the FRT. Our results suggest that BuBD-129 is a sperm-surface BD that could have a role in buffalo sperm function. Further studies elucidating its exact physiological function are required to better understand its role in the regulation of male fertility.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07640-z.

Benzo(a)pyrene suppresses tracheal antimicrobial peptide gene expression in bovine tracheal epithelial cells

Respiratory disease is an important cause of morbidity and mortality in cetaceans, which are also threatened by environmental degradation caused by crude oil spills. Following oil spills, cetaceans at the water surface may inhale droplets of oil containing toxic polycyclic aromatic hydrocarbons (PAHs), which could potentially alter respiratory immunity via activation of the aryl hydrocarbon receptor (AHR) and its subsequent interaction with nuclear factor kappa B (NF-κB). β-defensins are antimicrobial peptides secreted by airway epithelial cells and their expression is known to be dependent on NF-κB. We hypothesized that PAHs may suppress the expression of β-defensins, and thereby contribute to the pathogenesis of pneumonia. This hypothesis was modeled by measuring the in vitro effects of benzo(a)pyrene (BAP), phenanthrene, and naphthalene on tracheal antimicrobial peptide (TAP) gene expression in bovine tracheal epithelial cells. Stimulation with lipopolysaccharide (LPS) induced 20 ± 17-fold (mean ± SD) increased TAP gene expression. Exposure of tracheal epithelial cells to 5 μM BAP for 4 or 8 h, followed by incubation with a combination of LPS and 5 μM BAP for another 16 h, significantly (P = 0.002) suppressed LPS-induced TAP gene expression by 40.6 ± 21.8% (mean ± SD) in tracheal epithelial cells from 9 calves tested. BAP-induced suppression of TAP gene expression coincided with induction of cytochrome P450 1A1 gene expression. In contrast, phenanthrene and naphthalene had no consistent effect, and exposure to PAHs did not significantly affect constitutive TAP gene expression (i.e. without LPS). These findings characterize the suppressive effects of BAP-a toxic pollutant found in crude oil-on this respiratory innate immune response.

Human beta-defensin-2 and -3 enhance pro-inflammatory cytokine expression induced by TLR ligands via ATP-release in a P2X7R dependent manner

Our previous results indicate that HBD2 and HBD3 are chemotactic for a broad spectrum of leukocytes in a CCR6- and CCR2-dependent manner. In this study we report that pre-stimulation of primary human macrophages or THP-1 cells with HBD2 or HBD3 results in a synergistic, enhanced expression of pro-inflammatory cytokines and chemokines induced by TLR ligand re-stimulation. Experiments using specific inhibitors of the ATP-gated channel receptor P2X7 or its functional ligand ATP, suggest that the enhanced expression of pro-inflammatory cytokines and chemokines seems to be mediated by P2X7R. Furthermore, our data provide evidence that beta-defensins do not directly interact with P2X7R but rather induce the release of intracellular ATP. Interference with ATP release abrogated the synergistic effect mediated by HBD2 and HBD3 pre-stimulation in THP-1 cells. However, extracellular ATP alone seems not to be sufficient to elicit the enhanced synergistic effect on cytokine and chemokine expression observed by pre-stimulation of primary human macrophages or THP-1 cells with HBD2 or HBD3. Collectively, our findings provide new insights into the molecular mechanisms how HBD2 and HBD3 interact with cells of myeloid origin and demonstrate their immuno-modulating functions during innate immune responses.

DEFB1 polymorphisms and susceptibility to recurrent tonsillitis in Italian children

INTRODUCTION

The tonsils are secondary lymphoid organs fundamental for immune system response against pathogens within the oral cavity. Tonsillitis refers to inflammation of the pharyngeal tonsils that may include the adenoids and the lingual tonsils and that can be acute, recurrent, and chronic. Viral or bacterial infections, as well as immunologic factors are the main trigger to tonsillitis and disease's chronicity: the host immune responses, especially the innate one, could play an important role in susceptibility to the disease.

OBJECTIVES

The current study aims at investigating the role of functional polymorphisms in the 5'UTR (c.-52G>A, c.-44G>C and c.-20G>A) of DEFB1 gene, encoding for the antimicrobial peptide human beta-defensin 1, in the predisposition to recurrent tonsillitis in children from North Eastern Italy.

RESULTS

No significant correlation was found between DEFB1 allele, genotype and haplotype frequencies and recurrent tonsillitis susceptibility with the exception of an increased risk to disease development in patients carrying DEFB1 rare haplotypes.

CONCLUSION

Our results may suggest that DEFB1 polymorphisms alone may not influence pathology susceptibility, however they could possibly concur, together with other factors involved in the genetic control of innate immune system, in the predisposition towards recurrent tonsillitis.

PPARα agonists inhibit inflammatory activation of macrophages through upregulation of β-defensin 1

BACKGROUND

Effects of peroxisome proliferator-activated receptor alpha (PPARα) agonists on cardiovascular outcome have been controversial. Although these agents primarily affect lipoprotein metabolism, their pleiotropic anti-inflammatory effect is one of the potential anti-atherosclerotic mechanisms. This study aimed to evaluate the effect of fenofibrate and gemfibrozil on inflammation in macrophages and reveal pathways these agents may affect.

METHODS AND RESULTS

The two PPARα agonists inhibited secretion of CXCL2, TNF-α, IL-6, activation of p65 of NF-κB, ERK, and TLR4 expression. These changes occurred simultaneously with upregulation and secretion of β-defensin 1, an inflammation-modulating peptide. To demonstrate the role of β-defensin 1, it was knocked-down by target-specific siRNA. The effects of PPARα agonists on TLR4 expression and chemokine secretion were obviously abrogated with this treatment. In experiments investigating whether β-defensin 1 acts extracellularly, inflammatory chemokines decreased significantly after the addition of recombinant β-defensin 1 or conditioned media to cells. In experiments designed to clarify if the effects of the two agents are PPARα-dependent, induction of mRNA and secretion β-defensin 1 and inhibition of chemokine release were clearly reduced with GW6471, a PPARα blocker.

CONCLUSIONS

Our results reveal the pathways by which fenofibrate and gemfibrozil inhibit LPS-induced inflammatory activation of macrophages. This study elucidated a novel anti-inflammatory mechanism that acts through PPARα, β-defensin 1, and TLR4 pathways.

Surrounding cells affect the gene expression pattern of human beta-defensins in squamous cell carcinoma in vitro

BACKGROUND/AIM

Defensins are basic peptides involved in non-immune bio-defense mechanisms in a normal epithelium. Human oral squamous cell carcinoma cells (OSCC) also produce human beta-defensins (HBDs), although their exact function is not clear. This study aimed to analyze the variation in gene expression levels of hBDs in co-cultures of OSCC with murine cells.

MATERIALS AND METHODS

Two OSCC cell lines (HSC-3, HSC-4) were co-cultured with mouse embryonic fibroblasts, NIH/3T3 or a mouse chondrogenic cell line derived from teratocarcinoma, ATDC5, for 1.5 days. Expression patterns of the hBD genes were investigated by real-time polymerase chain reaction (RT-PCR).

RESULTS

hBD1 expression increased when co-cultured with NIH/3T3 but decreased when co-cultured with ATDC5. Expression of hBD2 and hBD4 tended to decrease. OSCC cells formed colonies when co-cultured with NIH/3T3 but were scattered when co-cultured with ATDC5.

CONCLUSION

hBDs expression in OSCC is dependent on the type of co-cultured cells and differences in gene expression may be responsible for the morphological differences observed. OSCC may produce HBDs for purposes other than bio-defense by surrounding cells.