Cardiometabolic risks and atherosclerotic disease in ApoE knockout mice: Effect of spinal cord injury and Salsalate anti-inflammatory pharmacotherapy

OBJECTIVE: To test in mice with a double mutation of the ApoE gene (ApoE(-/-)) whether spinal cord injury (SCI) hastens the native trajectory of, and established component risks for, atherosclerotic disease (AD), and whether Salsalate anti-inflammatory pharmacotherapy attenuates the impact of SCI. METHODS: ApoE(-/-) mice were anesthetized and underwent a T9 laminectomy. Exposed spinal cords were given a contusion injury (70 k-dynes). Sham animals underwent all surgical procedures, excluding injury. Injured animals were randomized to 2 groups: SCI or SCI(+Salsalate) [120 mg/Kg/day i.p.]. Mice were serially sacrificed at 20-, 24-, and 28-weeks post-SCI, and body mass was recorded. At sacrifice, heart and aorta were harvested intact, fixed in 10% buffered formalin, cleaned and cut longitudinally for en face preparation. The aortic tree was stained with oil-red-O (ORO). AD lesion histomorphometry was calculated from the proportional area of ORO. Plasma total cholesterol, triglycerides and proatherogenic inflammatory cytokines (PAIC’s) were analyzed. RESULTS: AD lesion in the aortic arch progressively increased in ApoE(-/-), significant at 24- and 28-weeks. AD in SCI is significantly greater at 24- and 28-weeks compared to time-controlled ApoE(-/-). Salsalate treatment attenuates the SCI-induced increase at these time points. Body mass in all SCI groups are significantly reduced compared to time-controlled ApoE(-/-). Cholesterol and triglycerides are significantly higher with SCI by 24- and 28-weeks, compared to ApoE(-/-), and Salsalate reduces the SCI-induced effect on cholesterol. PAIC’s interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor α (TNFα), monocyte chemoattractant protein-1 (MCP-1), and chemokine (C-C motif) ligand 5 (CCL-5) are significantly greater with SCI compared to ApoE(-/-) at varying timepoints. Salsalate confers a marginal reducing effect on PAIC’s by 28-weeks compared to SCI. Regression models determine that each PAIC is a significant and positive predictor of lesion. (p’s <0.05). CONCLUSIONS: SCI accelerates aortic AD and associated risk factors, and anti-inflammatory treatment may attenuate the impact of SCI on AD outcomes. PAIC’s IL-1β, IL-6, TNFα, MCP-1, and CCL-5 may be effective predictors of AD.