Carbohydrate source influences gelatinase production by mouse astrocytes in vitro

Molecular mediators of ischemic brain injury include intercellular adhesion molecule-1 (ICAM-1) and matrix metalloproteinase-9 (MMP-9), involved in the alteration of blood-brain barrier permeability and induced in astroglial cultures by tumor necrosis factor-alpha (TNF-alpha). Hyperglycemia is known to aggravate in vivo ischemic brain damage, while treatment with sorbitol shows benefit in reducing vasogenic brain edema. This study investigated whether a culture medium carbohydrate source could alter the astrocyte production of MMP-9 and ICAM-1 in vitro. The growth of astrocytes in 12.5 mM glucose, 25 mM glucose, or 25 mM sorbitol for 14 days did not alter cellular release of lactate dehydrogenase, uptake of Trypan blue, or surface expression of glial fibrillary acidic protein (GFAP). ICAM-1 levels were similar in astrocytes grown in glucose or sorbitol both under basal conditions and after TNF-alpha stimulation for 48 h. In contrast, levels of proMMP-9 released from astrocytes cultured for 14 days in 25 mM sorbitol reached only 55-28% of those obtained from cultures in 25 mM glucose after stimulation with 1,000 U/ml (P = 0.05) or 5,000 U/ml (P < 0.025) TNF-alpha, respectively. Limiting the duration of pre-stimulation sorbitol exposure to 48 h resulted in lower proMMP-9 levels than in glucose cultures after 5,000, but not 1,000, U/ml TNF-alpha, and differences were not significant when sorbitol exposure was further reduced to 24 h. Incubation in mixed glucose/sorbitol media did not affect the release of proMMP-9. These findings suggest that MMP-9 production may be increased in astrocytes as a consequence of glucose metabolism, which can be avoided by growth in sorbitol alone.