Cannabidiol Reduces Inflammatory Lung Damage After Meconium Aspiration in Newborn Piglets

Abstract

Aim: To assess the effects of cannabidiol (CBD) on lung damage in a piglet model of meconium aspiration syndrome (MAS).

Materials and methods: Meconium aspiration syndrome was modelled in newborn piglets via intratracheal instillation of 20% meconium in saline collected from healthy newborn humans. Piglets were treated i.v. with 5 mg/kg CBD (MAS + CBD) or Vehicle (MAS + VEH) 30 min after MAS induction and monitored for 6 h. Ventilated piglets without meconium instillation served as controls (CTL). Ventilatory and haemodynamic monitoring, histological and biochemical studies assessed the effects of treatment.

Results: Post-insult administration of CBD reduced MAS-induced deterioration of gas exchange, improving respiratory acidosis (final pH 7.38 ± 0.02, 7.22 ± 0.03 and 7.33 ± 0.03 and final pCO₂ 39.8 ± 1.3, 60.4 ± 3.8 and 45.7 ± 3.1 mmHg for CTL, MAS + VEH and MAS + CBD, respectively, p < 0.05). These beneficial effects were obtained despite the less aggressive ventilatory settings required for CBD-treated animals (final minute volume 230 ± 30, 348 ± 33 and 253 ± 24 mL/kg/min and final Oxygenation Index 1.64 ± 0.04, 12.57 ± 3.10 and 7.42 ± 2.07 mmHg for CTL, MAS + VEH and MAS + CBD, respectively, p < 0.05). CBD's beneficial effects on gas exchange were associated with reduced histological lung damage, reduced leucocyte infiltration and oedema (histopathological score 1.6 ± 0.3, 8.6 ± 1.4 and 4.6 ± 0.7 points for CTL, MAS + VEH and MAS + CBD, respectively, p < 0.05), as well as reduced TNFα production (0.04 ± 0.01, 0.34 ± 0.06 and 0.12 ± 0.02 A.U. for CTL, MAS + VEH and MAS + CBD, respectively, p < 0.05). Moreover, CBD improved blood pressure stability (final mean blood pressure 74.5 ± 0.2, 62.2 ± 6.2, and 78.67 ± 4.1 mmHg for CTL, MAS + VEH and MAS + CBD, respectively, p < 0.05).

Conclusion: Cannabidiol reduces histologic lung damage and inflammation in a piglet model of MAS. This translates into improved gas exchange and blood pressure stability.

Keywords: cannabidiol; inflammation; meconium aspiration syndrome (MAS); piglet; translational research.

FIGURE 1

Change over time on mean arterial blood pressure (MABP) in ventilated control (CTL, n = 6) animals and piglets submitted to meconium aspiration (MAS) and then treated with i.v. vehicle (VEH, n = 10) or CBD (n = 6). B, basal (pre-MAS); T, treatment administered (30 min after MAS). Data presented as mean ± SEM. Two-way ANOVA with Holm-Šidák’s post-hoc test for multiple comparisons. (*) p < 0.05 vs. CTH, (#) p < 005 vs. MAS + VEH.

FIGURE 2

Changes over time on blood gases (A) and ventilator settings (B,C) in ventilated control (CTL, n = 6) animals and piglets submitted to meconium aspiration (MAS) and then treated with i.v. vehicle (VEH, n = 10) or CBD (n = 6). B, basal (pre-MAS); T, treatment administered (30 min after MAS); Vt, tidal volume; MV, minute volume. Data presented as mean ± SEM. Two-way ANOVA with Holm-Šidák’s post-hoc test for multiple comparisons. (*) p < 0.05 vs. CTH, (#) p < 005 vs. MAS + VEH.

FIGURE 3

Histopathological score as assessed after haematoxylin-eosin staining in lung tissue from ventilated control (CTL, n = 6) animals and piglets submitted to meconium aspiration (MAS) and then treated with i.v. vehicle (VEH, n = 10) or CBD (n = 6). Top: Representative light microphotographs. In lung from MAS-VEH animals there is interstitial leukocyte infiltration, haemorrhage and interstitial oedema, which was reduced by CBD treatment. Original magnification x200, bar: 200 μm. Bottom: quantification of lung damage by a severity score. Results are expressed as mean ± SEM of 6–10 animals. (*) p < 0.05 vs. CTL, (#) p < 0.05 vs. MAS + VEH by one-way ANOVA with Holm-Šidák’s post-hoc test for multiple comparisons.

FIGURE 4

Concentration of TNFα as measured by western blot in lung tissue from ventilated control (CTL, n = 6) animals and piglets submitted to meconium aspiration (MAS) and then treated with i.v. vehicle (VEH, n = 10) or CBD (n = 6). Bars represent the mean (SEM) of 6–10 animals. Protein levels were normalised to β-actin loading and expressed as TNF-α/β-actin ratio. (*) p < 0.05 vs. CTL, (#) p < 0.05 vs. MAS + VEH by one-way ANOVA with Holm-Šidák’s post-hoc test for multiple comparisons.