Elevated cerebral spinal fluid cytokine levels in boys with cerebral adrenoleukodystrophy correlates with MRI severity

Abstract

Background: X-linked adrenoleukodystrophy (ALD) is a metabolic, peroxisomal disease that results from a mutation in the ABCD1 gene. The most severe course of ALD progression is the cerebral inflammatory and demyelinating form of the disease, cALD. To date there is very little information on the cytokine mediators in the cerebral spinal fluid (CSF) of these boys.

Methodology/principal findings: Measurement of 23 different cytokines was performed on CSF and serum of boys with cerebral ALD and patients without ALD. Significant elevations in CSF IL-8 (29.3±2.2 vs 12.8±1.1 pg/ml, p = 0.0001), IL-1ra (166±30 vs 8.6±6.5 pg/ml, p = 0.005), MCP-1 (610±47 vs 328±34 pg/ml, p = 0.002), and MIP-1b (14.2±1.3 vs 2.0±1.4 pg/ml, p<0.0001) were found in boys with cALD versus the control group. The only serum cytokine showing an elevation in the ALD group was SDF-1 (2124±155 vs 1175±125 pg/ml, p = 0.0001). The CSF cytokines of IL-8 and MCP-1b correlated with the Loes MRI severity score (p = 0.04 and p = 0.008 respectively), as well as the serum SDF-1 level (p = 0.002). Finally, CSF total protein was also significantly elevated in boys with cALD and correlated with both IL-8, MCP-1b (p = 0.0001 for both), as well as Loes MRI severity score (p = 0.0007).

Conclusions/significance: IL-8, IL-1ra, MCP-1, MIP-1b and CSF total protein were significantly elevated in patients with cALD; IL-8, MCP-1b, and CSF total protein levels correlated with disease severity determined by MRI. This is the largest report of CSF cytokine levels in cALD to date, and identification of these key cytokines will provide further insight into disease progression and perhaps lead to improved targeted therapies.

Figure 1. Serum SDF-1 is elevated in boys with cerebral ALD.

SDF-1 levels were determined by ELISA. Boxes show min and max, and the bar is at the mean. A Student's unpaired t-test calculated p-value shown.

Figure 2. CSF inflammatory cytokines are elevated in boys with cerebral ALD.

CSF cytokines were evaluated using a Lumunix system and SDF-1 by ELISA. Boxes show min and max, and the bar is at the mean. A Student's unpaired t-test calculated p-values shown.

Figure 3. Correlation of CSF MCP-1 levels and chitotriosidase activity.

Regression analysis was performed using CSF MCP-1 levels and CSF chitotriosidase activity as described by Orchard et al . Statistical analysis was performed using Prism software.

Figure 4. Correlation of serum SDF-1 levels and Loes MRI severity score.

Regression analysis was performed using serum SDF-1 levels and each patient's pretransplant Loes score using Prism software.

Figure 5. Correlation of CSF inflammatory cytokine levels and Loes MRI severity score.

Regression analysis was performed using the previously determined CSF cytokine levels and each patient's pretransplant Loes score using Prism software.

Figure 6. Elevated levels of CSF total protein correlate to IL-8, MCP-1, and Loes MRI severity score.

CSF total protein levels were taken from the patients' medical record. Boxes show min and max, and the bar is at the mean. Regression analysis was performed using the previously determined CSF cytokine levels for IL-8 and MCP-1 as well as each patient's pretransplant Loes score using Prism software.