Repeated intranasal exposure to microcystin-LR affects lungs but not nasal epithelium in mice. (15th September 2015) - Oliveira, Vinícius R.
Abstract: Microcystin-LR (MC-LR) is a harmful cyanotoxin able to induce adverse outcomes in the respiratory system. We aimed to examine the lungs and nasal epithelium of mice following a sub-chronic exposure to MC-LR. Swiss mice were intranasally instilled with 10 μL of distilled water (CTRL, n = 10) or 6.7 ng/kg of MC-LR diluted in 10 μL of distilled water (TOX, n = 8) during 30 consecutive days. Respiratory mechanics was measured in vivo and histology measurements (morphology and inflammation) were assessed in lungs and nasal epithelium samples 24 h after the last intranasal instillation. Despite the lack of changes in the nasal epithelium, TOX mice displayed an increased amount of PMN cells in the lungs (× 10 −3 /μm 2 ), higher lung static elastance (cmH2 O/mL), resistive and viscoelastic/inhomogeneous pressures (cmH2 O) (7.87 ± 3.78, 33.96 ± 2.64, 1.03 ± 0.12, 1.01 ± 0.08, respectively) than CTRL (5.37 ± 4.02, 26.65 ± 1.24, 0.78 ± 0.06, 0.72 ± 0.05, respectively). Overall, our findings suggest that the nasal epithelium appears more resistant than lungs in this model of MC-LR intoxication. Highlights: Exposure to repeated intranasal doses of microcystin-LR (MC-LR) and the effects in lungs and upper airways are reported. Mice were exposed to environmentally relevant concentrations of MC-LR. Deterioration of lung mechanical and histological parameters was observed. Histology measurements in the nasal cavity did not show any marked alteration. Nasal epithelium seems more resistant than lungs in this model of MC-LR exposure.