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Novel Cathelicidins from Pigeon Highlights Evolutionary Convergence in Avain Cathelicidins and Functions in Modulation of Innate Immunity.

Yu H, Lu Y, Qiao X, Wei L, Fu T, Cai S, Wang C, Liu X, Zhong S, Wang Y - Sci Rep (2015)

Bottom Line: In macrophages primed by LPS, Cl-CATH2 significantly down-regulated the gene and protein expressions of inducible nitric oxide synthase and pro-inflammatory cytokines while enhancing the anti-inflammatory cytokine, acting through MAPK and NF-κB signaling pathways.Molecular docking shows for the first time that cathelicidin binds to the opening region of LPS-binding pocket on myeloid differentiation factor 2 (MD-2) of toll-like receptor (TLR)4-MD-2 complex, which in turn inhibits the TLR4 pathway.Our results, therefore, provide new insight into the mechanism underlying the blockade of TLR4 signaling by cathelicidins.

View Article: PubMed Central - PubMed

Affiliation: School of Life Science and Biotechnology, Dalian University of Technology, Dalian, Liaoning 116024, China.

ABSTRACT
Cathelicidins are short cationic host defense peptides and play a central role in host innate immune system. Here we identified two novel cathelicidins, Cl-CATH2 and 3, from Columba livia. Evolutionary analysis of avian cathelicidins via phylogenetic tree and Ka/Ks calculations supported the positive selection that prompted evolution of CATH2 to CATH1 and 3, which originate from common ancestor and could belong to one superfamily. Cl-CATH2 and 3 both adopt amphipathic α-helical comformations identified by circular dichroism and the 3D structures built by Rosetta. Cl-CATH2 of CATH2 family with the most expression abundance in bird, exhibited relatively weak antimicrobial activity, but acted instead on the innate immune response without showing undesirable toxicities. In macrophages primed by LPS, Cl-CATH2 significantly down-regulated the gene and protein expressions of inducible nitric oxide synthase and pro-inflammatory cytokines while enhancing the anti-inflammatory cytokine, acting through MAPK and NF-κB signaling pathways. Molecular docking shows for the first time that cathelicidin binds to the opening region of LPS-binding pocket on myeloid differentiation factor 2 (MD-2) of toll-like receptor (TLR)4-MD-2 complex, which in turn inhibits the TLR4 pathway. Our results, therefore, provide new insight into the mechanism underlying the blockade of TLR4 signaling by cathelicidins.

No MeSH data available.


Related in: MedlinePlus

Effects of Cl-CATH2 on innate immune response signaling pathways.Raw 264.7 macrophage cells were treated with or without LPS and/or Cl-CATH2 of indicated concentration. Expression of specific proteins p38, JNK1/2, ERK1/2 and IκBα was tested by western-blotting.
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f7: Effects of Cl-CATH2 on innate immune response signaling pathways.Raw 264.7 macrophage cells were treated with or without LPS and/or Cl-CATH2 of indicated concentration. Expression of specific proteins p38, JNK1/2, ERK1/2 and IκBα was tested by western-blotting.

Mentions: Studies were undertaken to probe the mechanism by which Cl-CATH2 regulated the innate immune responses in bird. Once the LPS, one of the most potent immunostimulants, is recognized by TLR4 on assorted cells (macrophages, dendritic cells, B cells, specific types of T cells, fibroblasts and epithelial cells)39, the innate immune responses are triggered via the TLR signaling. Thereby, the effects of Cl-CATH2 on the TLR4-mediated immune response were examined. Results indicated that Cl-CATH2 substantially inhibited p38, ERK1/2 and JNK1/2 of the mitogen-activated protein kinase (MAPK) signaling in a concentration-dependent manner (Fig. 7). At Cl-CATH2′s concentration of 20 μg/ml, p-p38 and p-ERK1/2 were suppressed by 83% and 92%/82%, respectively. The p-JNK1/2 induced by LPS was almost completely blocked (98.2%/98.4%) by Cl-CATH2 of 20 μg/ml. To further investigate whether Cl-CATH2 ultimately blocks the activation of NF-κB, the effect of Cl-CATH2 on the IκBα degradation was determinated. IκB is a cytoplasmic protein complex that inactivates NF-κB. Cl-CATH2 of 5, 10 and 20 μg/ml inhibited the LPS-induced degradation of IκBα by 2.29, 2.77 and 2.53 fold, respectively (Fig. 7). Comparatively, LL37 (10 μg/ml) was reported to only slightly increase the phosphorylation of NF-κB, p6521.


Novel Cathelicidins from Pigeon Highlights Evolutionary Convergence in Avain Cathelicidins and Functions in Modulation of Innate Immunity.

Yu H, Lu Y, Qiao X, Wei L, Fu T, Cai S, Wang C, Liu X, Zhong S, Wang Y - Sci Rep (2015)

Effects of Cl-CATH2 on innate immune response signaling pathways.Raw 264.7 macrophage cells were treated with or without LPS and/or Cl-CATH2 of indicated concentration. Expression of specific proteins p38, JNK1/2, ERK1/2 and IκBα was tested by western-blotting.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508531&req=5

f7: Effects of Cl-CATH2 on innate immune response signaling pathways.Raw 264.7 macrophage cells were treated with or without LPS and/or Cl-CATH2 of indicated concentration. Expression of specific proteins p38, JNK1/2, ERK1/2 and IκBα was tested by western-blotting.
Mentions: Studies were undertaken to probe the mechanism by which Cl-CATH2 regulated the innate immune responses in bird. Once the LPS, one of the most potent immunostimulants, is recognized by TLR4 on assorted cells (macrophages, dendritic cells, B cells, specific types of T cells, fibroblasts and epithelial cells)39, the innate immune responses are triggered via the TLR signaling. Thereby, the effects of Cl-CATH2 on the TLR4-mediated immune response were examined. Results indicated that Cl-CATH2 substantially inhibited p38, ERK1/2 and JNK1/2 of the mitogen-activated protein kinase (MAPK) signaling in a concentration-dependent manner (Fig. 7). At Cl-CATH2′s concentration of 20 μg/ml, p-p38 and p-ERK1/2 were suppressed by 83% and 92%/82%, respectively. The p-JNK1/2 induced by LPS was almost completely blocked (98.2%/98.4%) by Cl-CATH2 of 20 μg/ml. To further investigate whether Cl-CATH2 ultimately blocks the activation of NF-κB, the effect of Cl-CATH2 on the IκBα degradation was determinated. IκB is a cytoplasmic protein complex that inactivates NF-κB. Cl-CATH2 of 5, 10 and 20 μg/ml inhibited the LPS-induced degradation of IκBα by 2.29, 2.77 and 2.53 fold, respectively (Fig. 7). Comparatively, LL37 (10 μg/ml) was reported to only slightly increase the phosphorylation of NF-κB, p6521.

Bottom Line: In macrophages primed by LPS, Cl-CATH2 significantly down-regulated the gene and protein expressions of inducible nitric oxide synthase and pro-inflammatory cytokines while enhancing the anti-inflammatory cytokine, acting through MAPK and NF-κB signaling pathways.Molecular docking shows for the first time that cathelicidin binds to the opening region of LPS-binding pocket on myeloid differentiation factor 2 (MD-2) of toll-like receptor (TLR)4-MD-2 complex, which in turn inhibits the TLR4 pathway.Our results, therefore, provide new insight into the mechanism underlying the blockade of TLR4 signaling by cathelicidins.

View Article: PubMed Central - PubMed

Affiliation: School of Life Science and Biotechnology, Dalian University of Technology, Dalian, Liaoning 116024, China.

ABSTRACT
Cathelicidins are short cationic host defense peptides and play a central role in host innate immune system. Here we identified two novel cathelicidins, Cl-CATH2 and 3, from Columba livia. Evolutionary analysis of avian cathelicidins via phylogenetic tree and Ka/Ks calculations supported the positive selection that prompted evolution of CATH2 to CATH1 and 3, which originate from common ancestor and could belong to one superfamily. Cl-CATH2 and 3 both adopt amphipathic α-helical comformations identified by circular dichroism and the 3D structures built by Rosetta. Cl-CATH2 of CATH2 family with the most expression abundance in bird, exhibited relatively weak antimicrobial activity, but acted instead on the innate immune response without showing undesirable toxicities. In macrophages primed by LPS, Cl-CATH2 significantly down-regulated the gene and protein expressions of inducible nitric oxide synthase and pro-inflammatory cytokines while enhancing the anti-inflammatory cytokine, acting through MAPK and NF-κB signaling pathways. Molecular docking shows for the first time that cathelicidin binds to the opening region of LPS-binding pocket on myeloid differentiation factor 2 (MD-2) of toll-like receptor (TLR)4-MD-2 complex, which in turn inhibits the TLR4 pathway. Our results, therefore, provide new insight into the mechanism underlying the blockade of TLR4 signaling by cathelicidins.

No MeSH data available.


Related in: MedlinePlus