NPY and CGRP Inhibitor Influence on ERK Pathway and Macrophage Aggregation during Fracture Healing.
OBJECTIVE
The aims of this study are to investigate the effects of neurotransmitters NPY and CGRP on ERK signaling in fracture healing, and to identify the correlation between macrophage aggregation and fracture healing.


METHODS
Male Sprague-Dawley rats were used to build a fracture model. The neurotransmitter receptor inhibitors were injected intraperitoneally into the rats. Immunofluorescence staining and ELISA were employed to determine the expression of NPY and CGRP in fracture area and the peripheral blood, respectively. Micro-CT together with histological staining were utilized to assess the fracture healing conditions. Relative protein expression was determined using western blot. Immunofluorescence staining was used to detect the aggregation of macrophages in the injury area.


RESULTS
During fracture healing, the serum NPY and CGRP significantly increased. The levels of NPY and CGRP reached a peak in the 8th week and reduced significantly thereafter. NPY and CGRP inhibitors could inhibit fracture healing and down-regulate the phosphorylated ERK. Macrophages (NPY+ and CGRP+) aggregated in the injury area.


CONCLUSIONS
NPY and CGRP participated in fracture healing, in which they were also shown to influence phosphorylated ERK expression. In addition, macrophages are involved in the fracture healing process.
Department of Trauma and Orthopaedics, Xijing Hospital, the Fourth Military Medical University, Xi'an, China.
Peng
P
Tang
Department of Trauma and Orthopaedics, Xijing Hospital, the Fourth Military Medical University, Xi'an, China.
Chunguang
C
Duan
Department of Trauma and Orthopaedics, Xijing Hospital, the Fourth Military Medical University, Xi'an, China.
Zheng
Z
Wang
Department of Trauma and Orthopaedics, Xijing Hospital, the Fourth Military Medical University, Xi'an, China.
ChunMei
C
Wang
Department of Trauma and Orthopaedics, Xijing Hospital, the Fourth Military Medical University, Xi'an, China.
Guolin
G
Meng
Department of Trauma and Orthopaedics, Xijing Hospital, the Fourth Military Medical University, Xi'an, China.
Kaifeng
K
Lin
Department of Ultrasonography, Xijing Hospital, the Fourth Military Medical University, Xi'an, China.
Qian
Q
Yang
Department of Trauma and Orthopaedics, Xijing Hospital, the Fourth Military Medical University, Xi'an, China.
Zhi
Z
Yuan
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000037:antagonists & inhibitors*; D017102:Fracture Healing / Q000187:drug effects*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D008264:Macrophages / Q000378:metabolism* / Q000473:pathology; D008297:Male; D009478:Neuropeptide Y / Q000037:antagonists & inhibitors*; D014179:Neurotransmitter Uptake Inhibitors / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D055114:X-Ray Microtomography
D009478:Neuropeptide Y; D014179:Neurotransmitter Uptake Inhibitors; D015740:Calcitonin Gene-Related Peptide
CGRP; ERK; Fracture Healing; Macrophage; NPY