α4β1 integrin blockade after spinal cord injury decreases damage and improves neurological function

The extent of disability caused by spinal cord injury (SCI) relates to secondary tissue destruction arising partly from an intraspinal influx of neutrophils and monocyte/macrophages after the initial injury. The integrin α4β1, expressed by these leukocytes, is a key to their activation and migration into/within tissue. Therefore, blocking this integrin's functions may afford significant neuroprotection. Rats were treated intravenously with a blocking monoclonal antibody (mAb) to the α4 subunit of α4β1 at 2 and 24 h after thoracic clip-compression SCI. Anti-α4β1 treatment significantly decreased neutrophil and monocyte/macrophage influx at 3 d by 47% and 53%, respectively, and decreased neutrophil influx by 61% at 7 d after SCI. Anti-α4β1 treatment also significantly reduced oxidative activity in injured cord homogenates at 3 d. For example, myeloperoxidase activity decreased by 38%, inducible nitric oxide by 44%, dichlorofluorescein (marking free radicals) by 33% and lipid peroxidation (malondialdehyde) by 42%. At 2–8 weeks after SCI, motor function improved by up to 2 points on an open-field locomotor scale. Treated rats supported weight with their hind paws instead of sweeping. At 2–4 weeks after SCI, anti-α4β1 treatment decreased blood pressure responses during autonomic dysreflexia by as much as 43% and, at 2–8 weeks, decreased mechanical allodynia elicited from the trunk and hind paw by up to 54% and 40%, respectively. This improved functional recovery correlated with spared myelin-containing white matter and > 10-fold more bulbospinal serotonergic axons below the injury than were in controls. The significant neurological improvement offered by this neuroprotective strategy underscores the potential for an anti-integrin treatment for SCI.