Retinal tissue develops an inflammatory reaction to tobacco smoke and electronic cigarette vapor in mice

Abstract

Cigarette smoke has been identified as a major risk factor for the development of age-related macular degeneration (AMD). As an alternative to conventional cigarettes (C-cigarette), electronic cigarettes (E-cigarette) have been globally promoted and are currently widely used. The increasing usage of E-cigarettes raises concerns with regard to short- (2 weeks), medium- (3 months), and long- (8 months) term consequences related to retinal tissue. In this report, a controlled study in mouse models was conducted to probe the comprehensive effects of E-cigarette vapor on retina, retinal pigmented epithelium (RPE), and choroidal tissues by (1) comparing the effects of C-cigarette smoke and E-cigarette vapor on retina separately and (2) determining the effects of E-cigarette vapor on the RPE and analyzing the changes with regard to inflammatory (IL-1β, TNFα, iNOS) and angiogenic (VEGF, PEDF) mediators in retina/RPE/choroid by ELISA assays. The data showed that C-cigarette smoke exposure promoted an inflammatory reaction in the retina in vivo. Mice exposed to E-cigarette (nicotine-free) vapor developed inflammatory and angiogenic reactions more pronounced in RPE and choroid as compared to retinal tissue, while nicotine-containing E-cigarette vapor caused even a more serious reaction. Both inflammatory and pro-angiogenic reactions increased with the extension of exposure time. These results demonstrate that exposure to C-cigarette smoke is harmful to the retina. Likewise, the exposure to E-cigarette vapor (with or without nicotine) increases the occurrence and progression of inflammatory and angiogenic stimuli in the retina, which might also be related to the onset of wet AMD in humans. KEY MESSAGES: C-cigarette smoke exposure promotes an inflammatory reaction in the retina in vivo. Mice exposed to E-cigarette (nicotine-free) vapor develop inflammatory and angiogenic reactions more pronounced in RPE and choroid compared to retinal tissue, while nicotine-containing E-cigarette vapor causes even a more serious reaction. Both inflammatory and pro-angiogenic reactions increase with the extension of E-cigarette vapor exposure time.

Keywords: AMD; Angiogenesis; C-cigarette smoke; E-cigarette vapor; Inflammatory reaction.

Fig. 1

Overview of the experimental groups. a C-cigarette exposure groups contain medium- and long-term subgroups and the corresponding control mice. b E-cigarette exposure groups contain short-, medium-, and long-term subgroups, wherein nicotine-free E-cigarette and nicotine-containing E-cigarette were used with the exception of the long-term subgroup, in which only nicotine-containing E-cigarettes was used. The number of eyes per group is listed in the grey box below each group

Fig. 2

Protein levels in the retina of mice from the C-cigarette smoke exposure (medium-, long-term) subgroups. Data presented are from factors IL-1β (a), iNOS (b), TNF-α (c) and VEGF (d), and PEDF (e). Ratio of VEGF vs PEDF reflects the changes to the equilibrium of both factors at the RPE/retina interface (f) reflects the comprehensive effect of pro-angiogenic. Data are presented as mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. LLD lower limit of detection

Fig. 3

Protein levels in the retina of mice from the E-cigarette vapor exposure (short-, medium-, long-term) subgroups. Data presented are from factors IL-1β (a), iNOS (b), TNF-α (c) and VEGF (d), and PEDF (e). Ratio of VEGF vs PEDF reflects the changes to the equilibrium of both factors at the RPE/retina interface (f) reflects the comprehensive effect of pro-angiogenic. Data are presented as mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. LLD lower limit of detection

Fig. 4

Protein levels in the RPE (a−f) and choroid (g−l) of mice from the E-cigarette exposure (medium-, long-term) subgroups. Data presented are from factors IL-1β (a, g), iNOS (b, h), TNF-α (c, i), VEGF (d, j), and PEDF (e, k). Ratio of VEGF vs PEDF reflects the changes to the equilibrium of both factors at the RPE/retina interface (f, l) reflects the comprehensive effect of pro-angiogenic. All the data are presented as mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. LLD, lower limit of detection

Fig. 5

Comparison of the percentage changes in inflammation-related (a IL-1β, b TNF-α, c iNOS) and angiogenesis-related cytokines (d VEGF, e PEDF, f ratio of VEGF vs. PEDF). Protein levels were compared between C-cigarette smoke and E-cigarette vapor subgroups. CC: C-cigarette smoke, EC-0 mg NT: E-cigarette (nicotine free) vapor, EC-18 mg NT: E-cigarette (nicotine containing) vapor, M: medium-term, L: long-term