MMP9 and infectious meningitis: In a mouse model of meningitis induced by LPS, melatonin (5 mg/kg) significantly attenuated cerebral MMP-9 activity following brain inflammation; and in the RAW264.7 and BV2 cells, the results showed that pretreatment or cotreatment with melatonin effectively inhibited LPS-induced MMP-9 activation [96].