Infection of stationary human brain aggregates with HIV-1 SF162 and IIIB results in transient neuronal damage and neurotoxicity.

The cellular basis of HIV associated dementia has been correlated with microglial activation and neuronal dysfunction in symptomatic HIV-1 disease. As a cellular model of HIV-1 infection of brain tissue in vitro, we established a stationary human brain aggregate (SHBA) system to compare infection of HIV-1 SF162 (R5 virus) to that of IIIB (X4 virus). Aggregates were analysed by immunohistochemistry, morphometry, flow cytometry and p24 ELISA. SHBAs had a 1 mm(3) size with a mixed cellular composition of 36% neurones, 27% astrocytes, 2% macrophages/microglia and 14% oligodendrocytes. Infection of SHBA's with the R5 HIV-1 SF162 virus led to the expression of HIV-1 p24 antigen in 6% of cells. Infection with this R5 using virus culminated in transient neuronal damage and a decrease in mitotically active progenitor cells within aggregates. Infection with X4 using HIV-1 IIIB was associated with astrocytosis and neurotoxicity. We propose that: (1) the pattern of cellular damage elicited by HIV-1 infection of brain tissue in vitro depends on virus subtype as determined by its preferential use of R5 or X4 chemokine receptors for entry into cells; (2) SHBAs are a reliable and readily established model of the cellular complexity of human brain tissue in vitro.

Evaluation of the effects of swainsonine, captopril, tangeretin and nobiletin on the biological behaviour of brain tumour cells in vitro.

Although intrinsic tumours of the brain seldom metastasize to distant sites, their diffuse, infiltrative-invasive growth within the brain generally precludes successful surgical and adjuvant therapy. Hence, attention has now focused on novel therapeutic approaches to combat brain tumours that include the use of anti-invasive and anti-proliferative agents. The effect of four anti-invasive agents, swainsonine (a locoweed alkaloid), captopril (an anti-hypertensive drug), tangeretin and nobiletin (both citrus flavonoids), were investigated on various parameters of brain tumour invasion such as matrix metalloproteinase (MMP) secretion, migration, invasion and adhesion. A standard cytotoxicity assay was used to optimize working concentrations of the drugs on seven human brain tumour-derived cell lines of various histological type and grade of malignancy. A qualitative assessment by gelatin zymography revealed that the effect of these agents varied between the seven cell lines such that the low grade pilocytic astrocytoma was unaffected by three of the agents. In contrast, downregulation of the two gelatinases, MMP-2 and MMP-9 was seen in the grade 3 astrocytoma irrespective of which agent was used. Generally, swainsonine was the least effective whereas the citrus flavonoids, particularly nobiletin, showed the greatest downregulation of secretion of the MMPs. Furthermore, captopril and nobiletin were most efficient at inhibiting invasion, migration and adhesion in four representative cell lines (an ependymoma, a grade II oligoastrocytoma, an anaplastic astrocytoma and a glioblastoma multiforme). Yet again, the effects of the four agents varied between the four cell lines. Nobiletin was, nevertheless, the most effective agent used in these assays. In conclusion, the differential effects seen on the various parameters studied by these putative anti-invasive agents may be the result of interference with MMPs and other mechanisms underlying the invasive phenotype. From these pilot studies, it is possible that these agents, especially the citrus flavonoids, could be of future therapeutic value. However, further work is needed to validate this in a larger study.

Extracellular matrix-modulated differential invasion of human meningioma cell lines in vitro.

The in vitro invasive behaviour of six meningioma cell lines of various histological sub-type and grade was assessed using Boyden chemotaxis chambers ('Transwell' units) precoated with various extracellular matrix proteins. The cell lines included a benign meningothelial (IPGS), two benign transitional (IPCBR and IPGC), one atypical (IPIH) and two malignant (IPSE and IPIR) meningiomas. IPGC was a recurrent tumour. The results showed that IPCBR was most invasive through laminin and vitronectin. IPIH was moderately invasive through collagen type IV, laminin, vitronectin and fibronectin. However, both IPSE and IPIR were less invasive than IPIH whereas, IPGS was least invasive of all. Moreover, laminin was the most permissive extracellular matrix protein for most cell lines and collagen type IV, the least permissive. These results show that there is a differential in vitro invasive behaviour of cell lines derived from different histological types of meningiomas according to extracellular matrix substrate and suggests that invasion and migration of meningiomas in situ might be modulated by various extracellular components.