title: Increased Thymic Cell Turnover under Boron Stress May Bypass TLR3/4 Pathway in African Ostrich.
abstract: 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.
authors.affiliation: Department of Anatomy, Histology and Embryology, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China.
authors.forename: Hai-bo
authors.initials: HB
authors.lastname: Huang
authors.affiliation: Department of Anatomy, Histology and Embryology, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China.
authors.forename: Ke
authors.initials: K
authors.lastname: Xiao
authors.affiliation: Department of Anatomy, Histology and Embryology, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China.
authors.forename: Shun
authors.initials: S
authors.lastname: Lu
authors.affiliation: Department of Anatomy, Histology and Embryology, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China.
authors.forename: Ke-li
authors.initials: KL
authors.lastname: Yang
authors.affiliation: Department of Anatomy, Histology and Embryology, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China.
authors.forename: Abdur Rahman
authors.initials: AR
authors.lastname: Ansari
authors.affiliation: Department of Anatomy, Histology and Embryology, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China.
authors.forename: Haseeb
authors.initials: H
authors.lastname: Khaliq
authors.affiliation: Department of Anatomy, Histology and Embryology, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China.
authors.forename: Hui
authors.initials: H
authors.lastname: Song
authors.affiliation: Department of Anatomy, Histology and Embryology, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China; Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, Alabama, United States of America.
authors.forename: Juming
authors.initials: J
authors.lastname: Zhong
authors.affiliation: Department of Anatomy, Histology and Embryology, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China.
authors.forename: Hua-zhen
authors.initials: HZ
authors.lastname: Liu
authors.affiliation: Department of Anatomy, Histology and Embryology, College of Animal Science and Veterinary Medicine, Huazhong Agricultural University, Wuhan, Hubei, People's Republic of China.
authors.forename: Ke-mei
authors.initials: KM
authors.lastname: Peng
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D001343:Autophagy / Q000235:genetics; D001483:Base Sequence; D001717:Birds / Q000502:physiology*; D001895:Boron / Q000378:metabolism*; D049109:Cell Proliferation; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D015870:Gene Expression; D008969:Molecular Sequence Data; D010802:Phylogeny; D015398:Signal Transduction; D013312:Stress, Physiological; D013950:Thymus Gland / Q000166:cytology* / Q000502:physiology; D051196:Toll-Like Receptor 3 / Q000235:genetics / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; D001895:Boron