CB2R agonist prevents nicotine induced lung fibrosis

Nicotine stimulates fibroblast proliferation while increasing inflammation and fibrosis of tissues. The cannabinoid receptor 1 (CB1R) is mainly located in the CNS, while cannabinoid receptor 2 (CB2R) is located in the immune cells within the body. CB2R regulates inflammatory processes and fibroblast function.

We investigated the impact of CB2R agonist, JWH 133 and the antagonist, AM630 on lung tissue, applied directly before nicotine application.

40 mice were placed into 4 groups. The experimental groups received nicotine intraperitoneally at a dose of 0.05 mg/kg of body weight (BW) for 14 days. Group B also received AM630 (0.5mg/kg of BW), while Group A was administered with JWH133 (1 mg/kg of BW). Group N received nicotine alone. The Control group C received 0.9% NaCl. After decapitation, lung tissues were stained with H&E, Trichrome Masson's method, and IHC against CTGF and α-SMA. The digital image processing system Image J with the IHC profiler plugins was then employed, optical density and IHC optical density score were calculated.

In the N group, an increase in the thickness of alveolar spaces (9.16 SD4.95µm vs. 4.77SD2.99µm in the C group), leukocytes infiltration and collagen deposition has been observed(OD: 0.20 SD0.0vs 0.07SD0.04 in the C group). In the B group, the alveolar space thickness has been the highest (11.57SD8.13µm). Furthermore, in this group, hyperaemia, destruction of lung structure, hyperplasia of II type pneumocyte and interstitial fibrosis has been observed (OD: 0.23 SD0.08). In contrast, the lung tissue of the A group has had normal structure and the thinnest alveolar septum (3.88 SD2.64µm). The expression of CTGF and α-SMA has been the highest in the B group.

Nicotine induces interstitial lung fibrosis that is enhanced by the CB2R antagonist and diminished by the CB2R agonist. Therefore, the CB2R agonist may offer a protection against fibrosis.