Activation of Calcitonin Gene-Related Peptide Receptor during Ozone Inhalation Contributes to Airway Epithelial Injury and Repair

Abstract

The authors investigated the importance of the neuropeptide, calcitonin gene-related peptide (CGRP), in epithelial injury, repair, and neutrophil emigration after ozone exposure. Wistar rats were administered either a CGRP-receptor antagonist ) or saline and exposed to 8 hours of 1-ppm ozone or filtered air with an 8-hour postexposure period. Immediately after exposure, ethidium homodimer was instilled into lungs as a marker of necrotic airway epithelial cells. After fixation, airway dissected lung lobes were stained for 5'-bromo-2'-deoxyuridine, a marker of epithelial proliferation. Positive epithelial cells were quantified in specific airway generations. Rats treated with CGRP 8-37 had significantly reduced epithelial injury in terminal bronchioles and reduced epithelial proliferation in proximal airways and terminal bronchioles. Bronchoalveolar lavage and sections of terminal bronchioles showed no significant difference in the number of neutrophils emigrating into airways in CGRP 8-37 -treated rats. The airway epithelial cell line, HBE-1, showed no difference in the number of oxidant stress positive cells during exposure to hydrogen peroxide and a range of CGRP 8-37 doses, demonstrating no antioxidant effect of CGRP . We conclude that activation of CGRP receptors during ozone inhalation contributes to airway epithelial injury and subsequent epithelial proliferation, a critical component of repair, but does not influence neutrophil emigration into airways.

Transcriptome Profiling of the Newborn Mouse Lung Response to Acute Ozone Exposure

“…However, examination by electron microscopy showed clear alterations in the epithelial structure with enlarged intercellular space and disrupted junctions between adjacent cells in the tracheas of O 3 exposed newborn mice. This is in contrast to previous studies in adult rats where epithelial damage tended to occur more in distal airways than in the proximal airways after 8 h of exposure to 1000 ppb O 3 (Oslund et al, 2009). This apparent difference may be due to differences in the age of animals and duration of O 3 exposure.…”

“…In our newborn mouse model, the results of rt-qPCR showed that CGRP mRNA expression was increased significantly (1.92 ± 0.16-fold) but transiently at 6 h post-O 3 exposure. CGRP may play a role in epithelial injury and repair after O 3 exposure as recently suggested (Oslund et al, 2009). Our results also demonstrate increased expression of the neuropeptide GRP at 24 h post-O 3 exposure.…”

Intratracheal Administration of Mesenchymal Stem Cells Modulates Tachykinin System, Suppresses Airway Remodeling and Reduces Airway Hyperresponsiveness in an Animal Model

“…On the other hand, a protective role of neuropeptitergic system has also been documented. VIP influences many respiratory functions, protects bronchial epithelial cells against damage, produces airway relaxation, inhibits SMC proliferation and reduces inflammation [ 74 ]. CGRP regulates inflammation and promotes epithelial repair [ 75 ].…”

Neuropeptide stimulation of physiological and immunological responses in precision‐cut lung slices

“…Ex vivo treatment with CGRP increased SPC‐ir granule size and number, suggesting an effect on AT2 cell quantity and function. While CGRP has previously been shown to induce epithelial cell proliferation in cell lines, changes in SPC granule number and size have rarely been reported in PCLS (Dakhama et al., 2004; Fu et al., 2010; Kawanami et al., 2009; Li, Cohen, et al., 2020; Oslund et al., 2009). The change in SPC immunoreactivity in the tissue may indicate a change in tissue alveolar cell coverage because a greater number of observed granules and AT2 cells will result in less space for alveolar type 1 (AT1) projections.…”