Calcitonin gene-related peptide protects type II alveolar epithelial cells from hyperoxia-induced DNA damage and cell death

Abstract

Hyperoxia therapy for acute lung injury (ALI) may unexpectedly lead to reactive oxygen species (ROS) production and cause additional ALI. Calcitonin gene-related peptide (CGRP) is a 37 amino acid neuropeptide that regulates inflammasome activation. However, the role of CGRP in DNA damage during hyperoxia is unclear. Therefore, the aim of the present study was to investigate the effects of CGRP on DNA damage and the cell death of alveolar epithelial type II cells (AEC II) exposed to 60% oxygen. AEC II were isolated from 19–20 gestational day fetal rat lungs and were exposed to air or to 60% oxygen during treatment with CGRP or the specific CGRP receptor antagonist CGRP8–37. The cells were evaluated using immunofluorescence to examine surfactant protein-C and ROS levels were measured by probing with 2′,7′-dichlorofluorescin diacetate. The apoptosis rate and cell cycle of AEC II were analyzed by flow cytometry, and apoptosis was determined by western blotting analysis of activated caspase 3. The DNA damage was confirmed with immunofluorescence of H2AX via high-content analysis. The ROS levels, apoptotic cell number and the expression of γH2AX were markedly increased in the hyperoxia group compared with those in the air group. Concordantly, ROS levels, apoptotic cell number and the expression of γH2AX were significantly lower with a significant arrest of S and G2/M phases in the CGRP/O2 group than in the hyperoxia or CGRP8–37/O2 groups. CGRP was concluded to protect lung epithelium cells against hyperoxic insult, and upregulation of CGRP may be a possible novel therapeutic target to treat hyperoxic lung injury.

Phenotypes of Bronchopulmonary Dysplasia

“…Oxygen is a double-edged sword since the preterm infants do not have an adequate amount of endogenous antioxidants to deal with oxidant injury, further predisposing them to the development of BPD or NEC [ 133 , 134 ]. The influences on cell growth brought by hyperoxia are either from the accumulation of inflammatory mediators or direct insult from reactive oxygen species [ 135 ]. These reactive species cause damage to not only cellular macromolecules [ 136 , 137 ], but also at the nuclear or mitochondrial DNA level.…”

“…Other cells in the lung are also affected by hyperoxia. The lung epithelium presented with markedly increased apoptotic cell numbers in the hyperoxia group and can be protected by Calcitonin gene-related peptide [ 135 ]. Fibroblasts help maintain alveolar and bronchial integrity, but following hyperoxia, significant morphological changes occur, with decreased proliferation and increased cell size, leading to a pro-fibrotic stage and resulting in abnormal repair in the lung [ 140 ].…”

Triptolide sensitizes breast cancer cells to Doxorubicin through the DNA damage response inhibition

“…ATM alteration or insufficient expression is thought to be an important factor for cancer initiation and development. On the other hand, studies show that inhibition of ATM activity could be favorable for DNA‐damage based treatment including chemotherapy and radiotherapy . Moreover, higher ATM expression level in cancer cells is associated with drug resistance …”

The Wnt7b/β-catenin signaling pathway is involved in the protective action of calcitonin gene-related peptide on hyperoxia-induced lung injury in premature rats

“…Previous studies indicated that CGRP has a protective role against hyperoxia-induced DNA damage and lung injury in type II alveolar epithelial (AEC II) cells and neonatal rats [ 10 , 11 ]. Another previous report demonstrated that CGRP is associated with the regulation of inflammatory cytokines [ 12 ].…”