Cigarette smoke extract triggers neoplastic change in lungs and impairs locomotor activity through wnt3a-β-catenin signaling in aged COPD rodent model

Abstract

Background

Chronic cigarette smoking primes immense decline in lung functions and retardation of motor functions with increase in age. This raise the question of whether age status overwhelm the susceptibility to smoking induced lung inflammatory diseases and neuro-motor dysfunctions.

Methods

To study the hypothesis 11–12 month old aged wistar rats (n = 6) were administered cigarette smoke extract (CSE) through intraperitoneal route (0.5 ml/rat) twice a week for 2 months. Respiratory lung functions were measured through whole body plethysmography. Lung histopathological evaluation and neuronal degeneration were observed by using H&E, picrosirius red and nissl staining respectively. Motor function tests were done through panel of neuro-behavioral tests and protein expressions were performed in lung and brain tissue homogenates through western blotting.

Results

Sub-chronic CSE exposure worsened the lung functions including decreased tidal volume (p < 0.05), peak inspiratory flow (p < 0.05) and enhanced pause (p < 0.05). Grossly, solid neoplastic lesions were visible on the supra-lateral surface of the lungs of the CSE treated animals. Histopathological examination revealed immune cell infiltration, dominated with macrophages and alveolar type II cells stained positive for PCNA. Increased expression of BAX, PCNA, Wnt-3a, p-β-catenin (p < 0.05) was seen in the lungs of CSE treated aged animals. Elevated expression of inflammatory markers including NF-ϏB, TNF-α, TNF-R1, p-AKT was found in CSE treated lung tissues. Moreover, our result showed increased MCP-1, VEGF and IL-6 levels in BALF and plasma (p < 0.01) which might lead to neo-vascularization and excessive cell proliferation in lungs of CSE induced rats. Sub-chronic cigarette smoke exposure retarded the motor activity with suppression of D1 and D2 receptor expression in brain tissues. Brain tissue revealed the abundance of hyperchromatic and pyknotic nuclei suggesting neuronal degeneration.

Conclusion

So in conclusion, chronic cigarette smoking in old age creates susceptibility to fast onset of lung inflammatory diseases and neuro-motor retardation than their nonsmoker counterparts.

Keywords:

• Cigarette smoke extract
• aged rats
• motor activity impairment
• lung tumor
• inflammation
• neuronal degeneration

Acknowledgement

We would like to thank the Director of CSIR-Central Drug Research Institute (CDRI), Lucknow, India, for his constant support. This study was funded by Council of Scientific and Industrial Research (CSIR)-Central Drug Research Institute. The CSIR-CDRI communication number is 10097.

Disclosure statement

No potential conflict of interest was reported by the authors.