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

Autophagy in farm animals: current knowledge and future challenges

Autophagy (a process of cellular self-eating) is a conserved cellular degradative process that plays important roles in maintaining homeostasis and preventing nutritional, metabolic, and infection-mediated stresses. Surprisingly, little attention has been paid to the role of this cellular function in species of agronomical interest, and the details of how autophagy functions in the development of phenotypes of agricultural interest remain largely unexplored. Here, we first provide a brief description of the main mechanisms involved in autophagy, then review our current knowledge regarding autophagy in species of agronomical interest, with particular attention to physiological functions supporting livestock animal production, and finally assess the potential of translating the acquired knowledge to improve animal development, growth and health in the context of growing social, economic and environmental challenges for agriculture.Abbreviations: AKT: AKT serine/threonine kinase; AMPK: AMP-activated protein kinase; ASC: adipose-derived stem cells; ATG: autophagy-related; BECN1: beclin 1; BNIP3: BCL2 interacting protein 3; BVDV: bovine viral diarrhea virus; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CMA: chaperone-mediated autophagy; CTSB: cathepsin B; CTSD: cathepsin D; DAP: Death-Associated Protein; ER: endoplasmic reticulum; GFP: green fluorescent protein; Gln: Glutamine; HSPA8/HSC70: heat shock protein family A (Hsp70) member 8; IF: immunofluorescence; IVP: in vitro produced; LAMP2A: lysosomal associated membrane protein 2A; LMS: lysosomal membrane stability; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MDBK: Madin-Darby bovine kidney; MSC: mesenchymal stem cells; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; NBR1: NBR1 autophagy cargo receptor; NDV: Newcastle disease virus; NECTIN4: nectin cell adhesion molecule 4; NOD1: nucleotide-binding oligomerization domain 1; OCD: osteochondritis dissecans; OEC: oviduct epithelial cells; OPTN: optineurin; PI3K: phosphoinositide-3-kinase; PPRV: peste des petits ruminants virus; RHDV: rabbit hemorrhagic disease virus; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy.

The Immune Regulatory Effect of Boron on Ostrich Chick Splenic Lymphocytes

Boron is a trace element which plays important roles in immune response. The relationship between boron and splenic lymphocyte proliferation, apoptosis, secretion of cytokines, and genes potentially related to immune response in ostrich chicks were investigated in the present study. Different concentrations of boron (0, 0.01, 0.1, 0.5, 1, 5, 10, 25, 50, and 100 mmol/L) were applied to splenic lymphocytes of African ostrich, respectively. The effect of boron on lymphocyte proliferation was checked by the CCK-8 method. Flow cytometry was used to detect the effect of boron on apoptosis. The secretion levels of IL-6 and IFN-α were determined by ELISA. Splenic lymphocyte gene expression profiles of ostrich chicks treated with boron (0, 0.1, 100 mmol/L) were studied using RNA-seq technology. The results showed that cell proliferation increased with 0.01-10 mmol/L boron, when it was 25-100 mmol/L, the cell proliferation gradually decreased as the boron concentration increased. Apoptosis ratio in ostrich splenic lymphocytes was closely related to boron concentrations. 0.01- and 0.1-mmol/L boron inhibited apoptosis in splenic lymphocytes, whereas 1, 10, 50, and 100-mmol/L boron promoted apoptosis. As the concentration of boron increased, the secretion of IL-6 gradually decreased; IFN-α was initially increased and then decreased with boron concentrations increased, reaching the maximum level with 1 mmol/L boron. In terms of the RNA-Seq data, there was no differentially expressed gene between the 0- and 0.1-mmol/L boron-treated samples; 21 differentially expressed genes were found between the 0- and 100-mmol/L boron-treated samples; 43 differentially expressed genes were found between the 0.1- and 100-mmol/L boron-treated samples. Functional analysis of the differentially expressed genes by Gene Ontology verified multiple functions associated with immune response. Pathway analysis showed that systemic lupus erythematosus, alcoholism, viral carcinogenesis, and necroptosis pathway were the major enriched pathways, and BIRC2-3, FTH1, and IL-1β genes showed differential expression in necroptosis pathway. These results demonstrated that low concentrations (0.01-0.1 mmol/L) of boron may promote the proliferation and the secretion of cytokines, inhibit cell apoptosis of ostrich splenic lymphocytes by enhancing the function of the cell membrane and the activity of intracellular catalytic enzymes, whereas high-concentration (25-100 mmol/L) boron had opposite effects on cells. The necroptosis pathway might play a pivotal role in regulating the immune response of boron-treated splenic lymphocytes in ostrich chicks.

Transcriptional Study Revealed That Boron Supplementation May Alter the Immune-Related Genes Through MAPK Signaling in Ostrich Chick Thymus

The objective of this study is to construct a digital gene expression tag profile to identify genes potentially related to immune response in the ostrich. Exposure to boron leads to an immune response in the ostrich, although the underlying mechanism remains obscure. Thus, a dire need of biological resource in the form of transcriptomic data for ostriches arises to key out genes and to gain insights into the function of boron on the immune response of thymus. For this purpose, RNA-Seq analysis was performed using the Illumina technique to investigate differentially expressed genes in ostrich thymuses treated with different boric acid concentrations (0, 80, and 640 mg/L). Compared with the control group, we identified 309 upregulated and 593 downregulated genes in the 80 mg/L treated sample and 228 upregulated and 1816 downregulated genes in 640 mg/L treated sample, respectively. Trend analysis of these differentially expressed genes uncovers three statistically significant trends. Functional annotation analysis of the differentially expressed genes verifies multiple functions associated with immune response. When ostrich thymuses were treated with boron, expression changes were observed in genes predominantly associated with MAPK and calcium signaling pathways. The results of this study provide all-inclusive information on gene expression at the transcriptional level that further enhances our apprehension for the molecular mechanisms of boron on the ostrich immune system. The calcium and MAPK signaling pathways might play a pivotal role in regulating the immune response of boron-treated ostriches.

RNA-Seq-Based Gene Expression Pattern and Morphological Alterations in Chick Thymus during Postnatal Development

The thymus is a lobulated unique lymphoid immune organ that plays a critical role in the selection, development, proliferation, and differentiation of T cells. The thymus of developing chickens undergoes continued morphological alterations; however, the biomolecular and transcriptional dynamics of the postnatal thymus in avian species is not clear yet. Therefore, the thymuses from chickens at different stages of development (at weeks 0, 1, 5, 9, 18, and 27) were used in the present study. The RNA-seq method was used to study the gene expression patterns. On average, 24120819 clean reads were mapped, differentially expressed genes (DEGs) were identified on the basis of log values (fold change), including 744 upregulated and 425 downregulated genes. The expression pattern revealed by RNA-seq was validated by quantitative real-time PCR (qPCR) analysis of four important genes, which are PCNA, CCNA2, CCNB2, and CDK1. Thus, the current study revealed that during postnatal development, the thymus undergoes severe atrophy. Thymus structure was damaged and gene expression changed dramatically, especially at the 27^th week of age. Moreover, we found significant changes of several signaling pathways such as the cytokine-cytokine receptor interaction and cell cycle signaling pathways. Hence, it may be inferred that those signaling pathways might be closely related to the postnatal chicken thymus development.

Improved osteogenesis of boron incorporated calcium silicate coatings via immunomodulatory effects

Osteoimmunology has revealed the importance of a favorable immune response for successful biomaterial-mediated osteogenesis. Boron-incorporated calcium silicate (Ca₁₁ Si₄ B₂ O₂₂ , B-CS) coating has been reported as a potential candidate for improving osteogenesis in orthopedic applications in vitro. However, relatively little is known about its effects on the immune response and subsequent osteogenesis. In this work, the immunomodulatory properties of the B-CS coating and its specific mechanism of action were explored. We found that the B-CS coating decreased M1 polarization and converted macrophages to the M2 phenotype via restraining the toll-like receptor signaling pathway, thus inducing a significant reduction in pro-inflammatory cytokines and an increase in anti-inflammatory cytokines. Moreover, the B-CS coating inhibited osteoclastogenesis and osteoclastic activities by downregulating osteoclastogenic genes and inhibiting the RANKL/RANK system. BMP2 and VEGF were also significantly upregulated by macrophages and bone mesenchymal stem cells, leading to activation of the BMP2 signaling pathway and subsequent upregulation of osteogenesis-associated genes, finally promoting osteogenic differentiation. These findings show that the B-CS coating could be a promising coating material for hip and knee implants. Furthermore, incorporation of the element boron into bioceramic coatings could be a good strategy in the design of bone biomaterials with beneficial immune responses. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 12-24, 2019.

The importance of boron in biological systems

Boron is an essential element for plants and probably essential for human and animal health. Boron has a broad range of physiological effects on biological systems at low concentrations, whereas it is toxic to at high concentrations. Eventhough there are many studies on boron's biological effects and toxicity, more information is needed to understand the mechanisms of its action. The aim of the current work is to review boron's function, transport and toxicity in different biological systems.

Effect of Boron on Thymic Cytokine Expression, Hormone Secretion, Antioxidant Functions, Cell Proliferation, and Apoptosis Potential via the Extracellular Signal-Regulated Kinases 1 and 2 Signaling Pathway

Boron is an essential trace element in animals. Appropriate boron supplementation can promote thymus development; however, a high dose of boron can lead to adverse effects and cause toxicity. The influencing mechanism of boron on the animal body remains unclear. In this study, we examined the effect of boron on cytokine expression, thymosin and thymopoietin secretion, antioxidant function, cell proliferation and apoptosis, and extracellular signal-regulated kinases 1 and 2 (ERK1/2) pathway in the thymus of rats. We found that supplementation with 10 and 20 mg/L boron to the drinking water significantly elevated levels of interleukin 2 (IL-2), interferon γ (IFN-γ), interleukin 4 (IL-4), and thymosin α1 in the thymus of rats (p < 0.05), increased the number of positive proliferating cell nuclear antigen (PCNA⁺) cells and concentrations of glutathione peroxidase (GSH-Px) and phosphorylated extracellular signal-regulated kinase (p-ERK) (p < 0.05), and promoted mRNA expression of PCNA and ERK1/2 in thymocytes (p < 0.05). However, the number of caspase-3⁺ cells and the expression level of caspase-3 mRNA were reduced (p < 0.05). Supplementation with 40, 80, and 160 mg/L boron had no apparent effect on many of the above indicators. In contrast, supplementation with 480 and 640 mg/L boron had the opposite effect on the above indicators in rats and elevated levels of pro-inflammatory cytokines, such as interleukin 6 (IL-6), interleukin 1β (IL-1β), and tumor necrosis factor α (TNF-α) (p < 0.05). Our study showed that supplementation of various doses of boron to the drinking water had a U-shaped dose-effect relationship with thymic cytokine expression, hormone secretion, antioxidant function, cell proliferation, and apoptosis. Specifically, supplementation with 10 and 20 mg/L boron promoted thymocyte proliferation and enhanced thymic functions. However, supplementation with 480 and 640 mg/L boron inhibited thymic functions and increased the number of apoptotic thymocytes, suggesting that the effects of boron on thymic functions may be caused via the ERK1/2 signaling pathway.