TLR4 is constitutively expressed in chick thymic epithelial cells

The role of TLR4-mediated MyD88/TRAF6/NF-κB signaling and pIgR intestinal expression in chicks during Salmonella enteritidis infection

To observe the effect of Salmonella enteritidis (SE)-induced inflammation on pIgR expression in jejunum and ileum. Salmonella enteritidis was orally administered to 7-day old Hyline chicks, which were killed after 1d,3d,7d and 14d. The mRNA expression of TLR4,MyD88,TRAF6,NF-κB, and pIgR was detected by real-time RT-PCR, and pIgR protein was detected by Western blotting. The TLR4 signaling pathway was activated, the mRNA expression of the pIgR in jejunum and ileum was increased, and pIgR protein in jejunum and ileum was up-regulated by SE. In SE-treated chicks,the pIgR in jejunum and ileum was up-regulated on mRNA,and protein level,associated with activation of the TRL4-mediated MyD88/TRAF6/NF-κB signaling pathway, which identifies this as a novel pIgR-related pathway to TLR4 activation.

Epigenetic modifications in thymic epithelial cells: an evolutionary perspective for thymus atrophy

Background

The thymic microenvironment is mainly comprised of thymic epithelial cells, the cytokines, exosomes, surface molecules, and hormones from the cells, and plays a vital role in the development, differentiation, maturation and homeostasis of T lymphocytes. However, the thymus begins to degenerate as early as the second year of life and continues through aging in human beings, leading to a decreased output of naïve T cells, the limited TCR diversity and an expansion of monoclonal memory T cells in the periphery organs. These alternations will reduce the adaptive immune response to tumors and emerging infectious diseases, such as COVID-19, also it is easier to suffer from autoimmune diseases in older people. In the context of global aging, it is important to investigate and clarify the causes and mechanisms of thymus involution.

Main body

Epigenetics include histone modification, DNA methylation, non-coding RNA effects, and chromatin remodeling. In this review, we discuss how senescent thymic epithelial cells determine and control age-related thymic atrophy, how this process is altered by epigenetic modification. How the thymus adipose influences the dysfunctions of the thymic epithelial cells, and the prospects of targeting thymic epithelial cells for the treatment of thymus atrophy.

Conclusion

Epigenetic modifications are emerging as key regulators in governing the development and senescence of thymic epithelial cells. It is beneficial to re-establish effective thymopoiesis, identify the potential therapeutic strategy and rejuvenate the immune function in the elderly.

Novel mutations in the signal transducer and activator of transcription 3 gene are associated with sheep body weight and fatness traits

The signal transducer and activator of transcription 3 (STAT3) gene plays a crucial role in leptin-mediated energy metabolism, upon which the growth and development of animals depend. Nevertheless, no studies have reported the effects of STAT3 gene polymorphisms on body weight and fatness modulation in sheep. This study aimed to illustrate STAT3 mRNA expression across tissues and various developmental stages of sheep and to highlight the association of STAT3 gene polymorphisms with body weight and fat-related traits in sheep, in order to identify a genetic marker that may conceivably be of value for marker-assisted selection (MAS). This study revealed that STAT3 was differentially expressed across age and sex (p < 0.05), with higher expression in the ram liver. The abundant expression of STAT3 in the liver of male sheep and increased expression in the hypothalamus and longissimus dorsi muscle from birth to six months of age may indicate the vital role of the STAT3 gene in animal growth and development. Moreover, SNP association analysis also revealed that the novel SNPs of the STAT3 gene detected in this study showed a significant association with body weight and fatness traits (p < 0.05). In conclusion, the significant genetic effects of the STAT3 gene polymorphisms on sheep growth and development revealed that STAT3 could be a marker gene for the selection of growth-related traits in sheep.

The capability of coenzyme Q10 to enhance heat tolerance in male rabbits: evidence from improved semen quality factor (SQF), testicular oxidative defense, and expression of testicular melatonin receptor MT1

Heat stress (HS) has a great influence on the etiology of male infertility. Coenzyme Q10 (CoQ10), known to have powerful antioxidant effects, has been reported to have such actions that are effective to treat infertility caused by HS. The aim of the present study was to investigate the antioxidative effect of CoQ10 on sperm quality, testicular antioxidant activities, and male fertility under HS. For this purpose, 18 mature male rabbits (aged 22 wk) of the Sinai Gabali breed were equally divided into 3 groups and placed at temperature-humidity index of 29 for 8 wk at a farm. The supplementation of CoQ10 at 0, 10, and 20 mg/kg of body weight was done in the first, second, and third groups, respectively. The results showed that the supplementation of CoQ10 had significant (P < 0.05) effect on semen quality factor (SQF) and testicular antioxidant activities by the supplementation of CoQ10. Moreover, a significant improvement in the concentration of testosterone, integrity of testicular DNA, and the expression of melatonin receptors was also observed, which were consistent with a significant improvement in buck fertility. The prolificacy was significantly increased (P < 0.05) in females when inseminated from bucks that were treated with CoQ10. Our results suggest that CoQ10 tends to decrease oxidative stress by enhancing testicular antioxidant activities, which are considered the most important factors for a buck's fertility. Hence, CoQ10 could be a suitable feed supplement to increase fertility, through enhancing the semen quality, in male rabbits and reducing the harmful effects of HS.

Toll-like receptor signaling in thymic epithelium controls monocyte-derived dendritic cell recruitment and Treg generation

The development of thymic regulatory T cells (Treg) is mediated by Aire-regulated self-antigen presentation on medullary thymic epithelial cells (mTECs) and dendritic cells (DCs), but the cooperation between these cells is still poorly understood. Here we show that signaling through Toll-like receptors (TLR) expressed on mTECs regulates the production of specific chemokines and other genes associated with post-Aire mTEC development. Using single-cell RNA-sequencing, we identify a new thymic CD14⁺Sirpα⁺ population of monocyte-derived dendritic cells (CD14⁺moDC) that are enriched in the thymic medulla and effectively acquire mTEC-derived antigens in response to the above chemokines. Consistently, the cellularity of CD14⁺moDC is diminished in mice with MyD88-deficient TECs, in which the frequency and functionality of thymic CD25⁺Foxp3⁺ Tregs are decreased, leading to aggravated mouse experimental colitis. Thus, our findings describe a TLR-dependent function of mTECs for the recruitment of CD14⁺moDC, the generation of Tregs, and thereby the establishment of central tolerance.

Immune tolerance is mediated by the deletion of autoreactive T cells via medullary thymic epithelial cells (mTEC) and dendritic cells (DC), and by the induction of regulatory T cells (Treg). Here the authors show that mTEC receiving toll-like receptor signaling control the recruitment of CD14⁺Sirpα⁺ DC population that is capable of inducing Treg for establishing tolerance.

The capability of L-carnitine-mediated antioxidant on cock during aging: evidence for the improved semen quality and enhanced testicular expressions of GnRH1, GnRHR, and melatonin receptors MT 1/2

Precise natural anti-oxidative compounds have facilitated the research of infertile gametes and the development of novel bio-therapeutics, especially the molecules that are based on the reduction of oxidative stress, such as L-carnitine (LC). In addition to, the defect in the functioning of sperm mitochondrial and the decreasing seminal antioxidant ability due to aging, its essential role in permitting the mitochondrial import and oxidation of long chain fatty acids is worthy. Therefore, current study was designed to investigate the effects of dietary LC on semen quality, seminal antioxidant activity, and their implications for the fertility in aged cocks for 12 wk. Supplementation of the feed with two different doses of LC (50 and 150 mg/kg body weight/day) for 12 wk showed significantly increased in the reproductive activity of cock, in comparison to the control group. Seminal analysis showed that supplementation of LC significantly increased (P < 0.05) the sperm motility, concentration, livability, semen quality factor, seminal malondialdehyde concentration, catalase, and glutathione peroxidase activities. In addition, addition of LC significantly increased (P < 0.05) the plasma concentration of testosterone and prostaglandin E2 but posed no significant effect on the concentration of follicle-stimulating hormone. Furthermore, the findings of artificial insemination showed significant increased (P < 0.05) in the percentage of fertility in LC groups, while the percentage hatchability and mortality remained unchanged. Immunohistochemistry analysis revealed that LC significantly increased (P < 0.05) the testicular immunopositivity of MT1 and MT2. Moreover, the administration of LC to the aged cocks enhanced (P < 0.05) GnRH1 and GnRHR mRNA levels when compared with untreated cocks. The results of the present study suggest that LC treatment of aged cocks increases the seminal antioxidant enzymes and sexual hormones levels, which may improve the semen quality by increasing the expression of GnRH1 and melatonin receptors (MT1 and MT2) activities. Collectively, LC could be a suitable feed supplementation to increase reproductive activities through enhancing semen quality in aging cocks.

Effects of lipopolysaccharide on the histomorphology and expression of toll-like receptor 4 in the chicken trachea and lung

Endotoxin or lipopolysaccharide (LPS) exposure can cause injury to the respiratory airways and in response, the respiratory epithelia express toll-like receptors (TLRs) in many species. However, its role in the innate immunity in the avian respiratory system is poorly understood. The aim of the present study was to evaluate the effects of LPS on the chicken trachea and lung. After intraperitoneal LPS or saline injection, the trachea and lungs were harvested at 0, 12, 36 and 72 h (n = 6 at each time point) and histopathologically analysed using haematoxylin and eosin and periodic acid-Schiff staining, while TLR4 expression was determined by immunohistochemistry and secretory Immunoglobulin A (SIgA) levels by enzyme-linked immunosorbent assay. After LPS stimulation, we observed a remarkable decrease in the number of goblet cells along with obvious disruption and desquamation of the ciliated epithelium in the trachea, blurring of the boundary between pulmonary lobules, narrowed or indistinguishable lumen of the pulmonary atria and leukostasis in the lungs. Following LPS stimulation, TLR4 protein expression was up-regulated in both the trachea and the lungs and was found on the ciliated columnar cells as well as in the submucosa of the trachea, and in the lungs on parenchymal and immune cells. However, SIgA levels were only up-regulated in the trachea at 12 h following LPS stimulation. Hence, this report provides novel information about the effects of LPS on the microstructure of the lower respiratory tract and it is concluded that its intra-peritoneal administration leads to TLR4-mediated destruction of the tracheal epithelium and pulmonary inflammation along with increased SIgA expression in the tracheal mucosa.

Acute Thymic Involution and Mechanisms for Recovery

Acute thymic involution (ATI) is usually regarded as a virulence trait. It is caused by several infectious agents (bacteria, viruses, parasites, fungi) and other factors, including stress, pregnancy, malnutrition and chemotherapy. However, the complex mechanisms that operate during ATI differ substantially from each other depending on the causative agent. For instance, a transient reduction in the size and weight of the thymus and depletion of populations of T cell subsets are hallmarks of ATI in many cases, whereas severe disruption of the anatomical structure of the organ is also associated with some factors, including fungal, parasitic and viral infections. However, growing evidence shows that ATI may be therapeutically halted or reversed. In this review, we highlight the current progress in this field with respect to numerous pathological factors and discuss the possible mechanisms. Moreover, these new observations also show that ATI can be mechanistically reversed.

The several elements of intestinal innate immune system at the beginning of the life of broiler chicks

Functional capacity of digestive system and intestinal adaptive immunity are immature at hatching of broiler chicks. Therefore, intestinal innate immunity after hatching is vital to young chicks. The purpose of this study was to investigate expression and tissue distributions of several elements of the innate immune system (i.e., TLR2, TLR4, CD83, and MHC class II expressing cells) in the intestine of one-day-old chicks. For this purpose, ileum and cecum were examined the under different conditions, which included the control and 1, 3, 6, 12, or 24 h after injection of lipopolysaccharide (LPS) and phosphate buffered saline. The findings indicated that regardless of the antigenic stimulation, Toll-like receptor (TLR) 2 and TLR4 expressing cells were present in the intestinal tissues of one-day-old chicks. We noticed that the intestinal segments have different TLR expression levels after LPS stimulation. Dendritic cells were identified, and they left the intestinal tissue after LPS treatment. MHC class II molecules were diffusely present in both the ileum and cecum. This study demonstrates that the intestinal tissue of one-day-old chicks has remarkable defensive material, including histological properties and several elements of the innate immune system. Microsc. Res. Tech. 79:604-614, 2016. © 2016 Wiley Periodicals, Inc.

Increased Thymic Cell Turnover under Boron Stress May Bypass TLR3/4 Pathway in African Ostrich

Previous studies revealed that thymus is a targeted immune organ in malnutrition, and high-boron stress is harmful for immune organs. African ostrich is the living fossil of ancient birds and the food animals in modern life. There is no report about the effect of boron intake on thymus of ostrich. The purpose of present study was to evaluate the effect of excessive boron stress on ostrich thymus and the potential role of TLR3/4 signals in this process. Histological analysis demonstrated that long-term boron stress (640 mg/L for 90 days) did not disrupt ostrich thymic structure during postnatal development. However, the numbers of apoptotic cells showed an increased tendency, and the expression of autophagy and proliferation markers increased significantly in ostrich thymus after boron treatment. Next, we examined the expression of TLR3 and TLR4 with their downstream molecular in thymus under boron stress. Since ostrich genome was not available when we started the research, we first cloned ostrich TLR3 TLR4 cDNA from thymus. Ostrich TLR4 was close to white-throated Tinamou. Whole avian TLR4 codons were under purify selection during evolution, whereas 80 codons were under positive selection. TLR3 and TLR4 were expressed in ostrich thymus and bursa of fabricius as was revealed by quantitative real-time PCR (qRT-PCR). TLR4 expression increased with age but significantly decreased after boron treatment, whereas TLR3 expression showed the similar tendency. Their downstream molecular factors (IRF1, JNK, ERK, p38, IL-6 and IFN) did not change significantly in thymus, except that p100 was significantly increased under boron stress when analyzed by qRT-PCR or western blot. Taken together, these results suggest that ostrich thymus developed resistance against long-term excessive boron stress, possibly by accelerating intrathymic cell death and proliferation, which may bypass the TLR3/4 pathway. In addition, attenuated TLRs activity may explain the reduced inflammatory response to pathogens under boron stress.