Chemokine receptor CXCR3 is important for lung tissue damage and airway remodeling induced by short-term exposure to cigarette smoking in mice

Abstract

Aim: To investigate the role of chemokine receptor CXCR3 in cigarette smoking (CS)-induced pulmonary damage.

Methods: CXCR3 knockout (CXCR3-/-) mice were used. Differences in airspace enlargement, mRNA expression of matrix metalloproteinases (MMPs), transforming growth factor (TGF) beta1, CXCL10 in lung homogenates, and CXCL10 content in bronchoalveolar lavage (BAL) fluids and homogenates were compared between CXCR3-/- mice and wild-type (WT) mice three days after three-day CS exposures.

Results: The linear intercept was significantly less in CXCR3-/- mice than in WT mice (30.1+/-0.9 microm vs 40.3+/-2.4 microm, P<0.01). Morphologically, collagen was deposited less around airways and vessels in CXCR3-/- mice. The lung hydroxyproline content was significantly lower in CXCR3-/- mice than in WT mice (6.0+/-1.0 microg/mL vs 12.0+/-1.6 microg/mL, P<0.05). Profoundly lower mRNA expression of MMP2, MMP12, TGF beta 1, and CXCL10 was seen in lung homogenates from CXCR3-/- mice. CXCL10 concentrations in BAL fluid and lung homogenates were significantly lower in CXCR3-/- mice than in WT mice (BAL fluid: 19.3+/-1.4 pg/mL vs 24.8+/-1.6 pg/mL, P<0.05; lung homogenates: 76.6+/-7.0 pg/mL vs 119.5+/-15.9 pg/mL, P<0.05).

Conclusion: CXCR3 is important in mediating lung tissue damage and airway remodeling following a short-term CS insult, possibly through up-regulation of CXCL10 and inducement of mRNA expression of MMPs. Targeting CXCR3 may be helpful for prevention of CS-induced pulmonary pathology.

Figure 1

Effect of CXCR3 deletion on airspace enlargement at three days after the last CS exposure. (A) Morphometrical appearance of lungs from CXCR3-/- and WT mice (magnification ×40); the arrow points to the enlarged airspace in WT mice. n=8 mice/group. (B) Difference in Lm between CXCR3-/- and WT mice. Results are expressed as mean±SEM. n=6 mice/group, ^cP<0.01.

Figure 2

Effect of CXCR3 deficiency on mRNA expression of MMPs and TIMPs in lung homogenates at three days after the last CS exposure. (A) mRNA expression of MMP2, MMP9, and MMP12 in CXCR3-/- and WT mice, n=5 animals/group. (B) mRNA expression of TIMPs 1-4 in CXCR3-/- and WT mice, n=8 animals/group. Results are expressed as mean±SEM. ^bP<0.05.

Figure 3

Effect of CXCR3 deletion on mRNA expression in lung homogenates and production of CXCL10/IP-10 in BAL fluid and lung homogenates at three days after short-term CS exposure. (A) mRNA expression of CXCR3 ligands, n=5 animals/group. (B) mRNA expression of IFNγ, n=6 animals/group. (C) CXCL10/IP-10 concentration in BAL fluid and lung homogenates, n=8 animals/group. Results are expressed as mean±SEM. ^bP<0.05.

Figure 4

Effect of CXCR3 on airway remodeling at three days after the last CS exposure. (A) Histological appearance in CXCR3-/- and WT mice (magnification ×40); the arrows point to the collagen deposition around small airways and vessels in WT mice, n=5 mice/group. (B) Hydroxyproline content of lung tissue in CXCR3-/- and WT mice, n=6 mice/group. (C) Comparison of mRNA expression of TGFβ1 in lung homogenates between in CXCR3-/- and WT mice, n=8 mice/group. Results are expressed as mean±SEM. ^bP<0.05.

Figure 5

Effect of CXCR3 deficiency on protein leakage and TNFα concentration in BAL fluid at three days after the three-day CS insult. (A) Protein concentration in BAL fluid, n=5 mice/group. (B) TNFα content in BAL fluid, n=6 mice/group. Results are expressed as mean±SEM.