Chronically reduced IL-10 plasma levels are associated with hippocampal sclerosis in temporal lobe epilepsy patients.

BACKGROUND

Increasing evidence supports the role of soluble inflammatory mediators in the pathogenesis of refractory temporal lobe epilepsy (TLE). Hippocampal sclerosis (HS) is a well-described pathohistological abnormality in TLE. The association of proinflammatory cytokines with epileptic disease profiles is well established; however, the potential significance of circulating interleukin 10 (IL-10), particularly in TLE-associated HS, is still poorly understood. Therefore, taking into consideration the neuroprotective and anticonvulsive effects of IL-10, we performed this study to examine the role of the plasma levels of IL-10 in patients with TLE with HS (TLE + HS), TLE without HS (TLE-HS) and with other types of epilepsy.

METHODS

This study included 270 patients with refractory epilepsy who were classified into four groups: i) 34 patients with TLE + HS, ii) 105 patients with TLE-HS, iii) 95 patients with extra-TLE (XLE) and iv) 36 patients with idiopathic generalized epilepsy (IGE). The plasma IL-10 levels were quantified using a commercially available enzyme-linked immunosorbent assay (ELISA).

RESULTS

IL-10 levels were significantly lower in TLE + HS than in TLE-HS (p = 0.013). In a subgroup of TLE-HS patients who had seizures 1 month before sampling, patients with seizures had significantly higher IL-10 levels than patients who were seizure-free (p = 0.039). Among a small group (n = 15) of non-refractory TLE-HS patients, IL-10 levels showed a moderate negative correlation with the duration of epilepsy (r = - 0.585, p = 0.023).

CONCLUSIONS

This study demonstrated that chronically reduced levels of plasma IL-10 were associated with HS in TLE patients, suggesting that there was an inadequate systemic anti-inflammatory immune response. These results could provide new biological insights into the pathophysiology of HS in TLE. We also found that the production of IL-10 could be affected by the seizure frequency and declined concomitantly with increased disease durations. Therefore, the measurement of plasma IL-10 may have diagnostic value as a biomarker for stratifying TLE + HS from other epilepsy types or as a marker of disease progression towards a progressive form of epilepsy.