Lipid moiety of malarial pigment promotes MMP-9 activation and IL-8 release in human microvascular endothelial cells

Cerebral malaiia (CM) is a life-threatening encephalopathy caused by the cytoadherence of malaria-infected erythrocyte to brain endothelial cells followed by blood-brain barrier (BBB) damage, glial activation, inflammatory response an neurological sequelae. Here, we studied the effects of hemozoin (HZ), the malarial lipid-enriched ferriprotoporphyrin IX pigment, on MMP-9 activation and lL-8 release by human microvascular endothelial cells (HMECs), Cells were treated for 48 h with native (n) HZ, delipidized (d) HZ or lipid-free synthetic (s) HZ. As observed by optical microscopy, HMECs treated with nHZ appeared elongated; additionally, nHZ-treated cells were able to form microtubule-like vessels through Matrigel. Gelatin zymography showed that nHZ induced ex novo MMP-9 activity. Further investigation by western blotting suggested that nHZ also promoted proMMP-9 protein expression, as well as MMP-1 and MMP-3, two enzymes involved in the MMP-9 proteolytic activation cascade. Additionally IL-1β levels were enhanced by nHZ, as measured by ELISA. Interestingly the effects of nHZ were not reproduced by dHZ or sHZ. Collectively, present data suggest that lipid moiety of HZ promotes MMP-9 activity and IL-8 release in HMECs. As a consequence, cell invasiveness, tight junctions disruption and neutrophils monocytes recruitment might be favoured, concurring to BBB damage in CM.