G. Trillo-Pazos

Recombinant nef HIV-IIIB protein is toxic to human neurons in culture

The expression of HIV-1 negative factor (nef) has been positively correlated with HIV disease progression [Z. Hanna, D.G. Kay, N. Rebai, A. Guimond, S. Jothy, P. Jocicoeur, Nef harbors a makor determinant of pathogenicity for an AIDS-like disease induced by HIV-1 in transgenic mice. Cell 95 (1998) 163-175]. Nef expression has been detected in HIV infected human brains with neuronal damage [A. Ranki, M. Nyberg, V. Ovod, M. Haltia, I. Elovaara, R. Raininko, H. Haapsalo, K. Krohn, Abundant expression of HIV Nef and Rev proteins in brain astrocytes in associated with dementia, AIDS 9(9) (1995) 1001-1008; Y. Saito, L.R. Sharer, M.G. Epstein, J. Michaels, M. Mintz, M. Londer, K. Golding, B.M. Blumberg, Overexpression of nef as a marker for restricted HIV-1 infection of astrocytes in postmorten paediatric central tissues, Neurology 14 (1994) 474-480]. It is postulated that nef may contribute to the neuronal damage observed in the brain of those with late HIV disease. To test this, the potential toxicity of recombinant nef (from HIV-1 IIIB) was compared to the neurotoxin human tumour necrosis alpha (TNFalpha) on human brain cells in culture. SK-N-SH neuroblastoma, primary human neurons and glial cells were exposed to recombinant nef or TNFalpha protein for 3 days or twice over 6 days. Cell viability was assessed by Trypan Blue, lactate dehydrogenase (LDH) release and MTT assays. Nuclear fragmentation was detected using the Hoechst Blue nuclear dye assay. Both nef and TNFalpha (100 ng/ml) caused a significant 30% reduction of SK-N-SH cell numbers after 3 days exposure (P=0. 001). At this time, exposure to nef caused evident fragmented nuclei in these cultures. Human neuronal cultures had a 32 and 33% decrease in cell number after 6 days exposure to either nef or TNFalpha, respectively (P<0.001). Furthermore, as previously shown [J. He, C.M. DeCastro, G.R. Vandenbark, J. Busciglio, D. Gabuzda, Astrocyte apoptosis induced by HIV-1 transactivation of the c-kit protoonocogene, Proc. Natl. Acad. Sci. 94 (1997) 3954-3959], a 3-day exposure to nef significantly reduced human glial cell number by 25% (P=0.001). Recombinant nef and TNFalpha compromise human neurons in culture. Thus, like other virotoxins, it is shown for the first time that nef may also contribute to neuronal damage that has been reported in dementia in late HIV disease.

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.

The role of integrin receptors in aspects of glioma invasion in vitro

Integrins are heterodimers consisting of non‐covalently associated alpha and beta subunits. They mediate adherence of normal and tumour cells to the extracellular matrix, a property which is essential for migration of neoplastic astrocytes as they invade into the normal brain parenchyma. Flow cytometry and immunocytochemical analysis of cultured cells derived from 10 gliomas (1 pilocytic astrocytoma, 1 astrocytoma, 1 oligoastrocytoma, 1 anaplastic oligoastrocytoma, 4 anaplastic astrocytomas and 2 glioblastoma multiforme) revealed that the β1 integrin subunit was generally expressed more strongly than α4 or αv integrin subunits. Subsequent studies with function‐blocking antibodies against the β1 subunit inhibited adhesion, motility and invasion of the gliomas in vitro, to varying degrees, on all extracellular matrix substrates investigated (laminin, collagen type IV, fibronectin and vitronectin), the inhibition by β1 subunit was greatest on collagen type IV. These studies therefore substantiate the case for a role of the β1 integrin subunit in neoplastic glial cell invasion of the brain.

From human immunodeficiency virus (HIV) infection of the brain to dementia.

Human immunodeficiency virus (HIV) can cause both primary and secondary brain diseases. Numerous neuropathological studies have shown that up to 90% of patients with acquired immune deficiency syndrome (AIDS) have lesions in the nervous system. In this review, we discuss the entry of HIV into the brain, the general features of HIV associated neuropathology, the role of different brain cells in HIV mediated neuronal damage, and the putative molecular mechanisms involved. We conclude by correlating which factors might be important in the development of HIV associated dementia.

Neuronal Damage and Its Relation to Dementia in Acquired Immunodeficiency Syndrome (AIDS)

There are an estimated 21.8 million people infected with human immunodeficiency virus (HIV) worldwide [Weekly Epidemiol Rec 1996; 27:204-208] and 90% of these people will have some form of neuropathological abnormality during the course of acquired immunodeficiency syndrome (AIDS). In this review, we will highlight the primary HIV-associated brain disorders. The role of HIV proteins and cytokines on neuronal damage will be assessed. We will also discuss the role of neuronal loss and functional damage in HIV-associated dementia.