The effect of cigarette smoke exposure on spinal cord injury in rats

In this study, we examined whether cigarette smoke has neuroprotective or toxic effects on spinal cord injury (SCI). Male Sprague-Dawley rats were included in the study and received either cigarette smoke exposure or fresh air exposure. Twenty-four hours after the last cigarette smoke or fresh air exposure, all rats were injured at thoracic level 12 (T12), using an established static compression model. Our data showed that the cigarette smoke group had higher water content; higher permeability of the blood-spinal cord barrier (BSCB); higher malondialdehyde (MDA) levels, aquaporin-4 (AQP4) and hypoxia-inducible factor 1-alpha (HIF-1α) protein expression, and mRNA levels; and lower glutathione (GSH) levels than the control group values at 12 h, 24 h, and 48 h after SCI. There was no significant difference in these between the cigarette smoke group and the control group at 0 h after SCI. The results of the Basso, Beattie, and Bresnahan (BBB) hindlimb locomotor rating scale showed that rats in the cigarette smoke group had greater dysfunction in hindlimb movement than did rats in control group from 2 to day 6 after SCI. The extent of recovery did not make any difference from day 7 to day 10 after SCI between the cigarette smoke group and the control group. These results suggested that cigarette smoke can reinforce the oxidative stress injury via HIF-1α and AQP4 in the early stage after SCI. It is possible that cigarette smoke exposure does not affect SCI recovery in the long term; however, it can aggravate the edema and deteriorate BSCB disruption via HIF-1α and AQP4 in the early stage after SCI. More studies will be essential to consider this hypothesis and elucidate the mechanisms involved.