THIRD INTERNATIONAL CONFERENCE ON ALZHEIMER’S DISEASE

hypothesis that, the AM-induced production of NFT may be InhIbited or rnhancrd.

by the chronic edmlnlstratlon of drug,, we tried to verify this hypothesis for the

neuroteptics. chronically administered to schizophrenics since 1953, and we

investigated for the presence of AMSP and NFT. all the brains of schizophrenics who

died at more than 70 years, and came to autopsy in the psychiatric hosptial of Geneva:

41 of them non treated by neuroleptics (dead from 1932 through 1952) and 61

treated by neuroleptics (dead from 1953 through 1990). The mean age at death of the

lwo groups being identical, about 79 years, as was also the incidence of AMSP: 60%

in both groups, identical to that observed in the general population of same age in

Geneva, the incidence of NFT smong the brains presenting AM.SP, has been found

to be hvlce hlghor In the group treated by neuroleptics then In the group non

treated (74% versus 36% p<O.O5). It may be concluded that the AM is formed in the

brains of elderly schizophrenics with the same frequency as in the general population

and without interference with the neuroleptic treatment, and that nouroloptlcs may

enhance the AM-Induced disturbances leading to the formation of the NFT.

Potential for therapeutic Intervention: the chronic administration of other

drugs (to be discovered) may lnhlblt the AM-induced production 01 the NFT, related

to the cllnlcel Symptoms of dementlb. and therefore, prevent, stopordelaythem.

1979: Schweiz. Arch. Neural. Psychiat. 124: 317-333: 1985: Alzheimer’s disease. in Handb.

Clin. New-al. 46: 247.282; 1988: Alz. Dis. Ass. Disord. 2: 224; I9 8 9: J. Neural. Transm. (P-O)

1: 7; 19 9 1: Nature 353: 432433.

549 SERUM ALUMINUM-BINDING PROTEINS: CRARACTRRIZATION OF ALBINDIN, A NEW CARRIER PROTEIN, C. Mizzen, M. Favarato*, E. Jaikaran, B. Krishnan, T. Kruck and D. McLachlan. Centre for Research in Neurodegenerative Diseases; University of Toronto, Toronto, Ontario, Canada M5S JAB and *Department of Biology; University of Padova, 35131 Padova, Italy.

Elevated levels of aluminum in post-mortem brain is a common feature of Alzheimer's disease (AD) and suggests that aluminum may participate in the etiopathogenesis of AD. To investigate the role of serum aluminum in AD pathogenesis, we have developed a size exclusion chromatography (SEC) method for monitoring aluminum speciation in serum. This method reveals that two principle carriers of serum aluminum exist in most individuals, transferrin and a fraction we have named albindin. Albindin is proteinaceous and does not appear to be related to transferrin. The ap- parent molecular mass of aluminum-albindin complexes is approximately 5,300 daltons. Aluminum binding by albindin in vitro does not require exogenous bicar- bonate and aluminum-albindin complexes resist chela- tion in vitro by EDTA and desferrioxamine. Typically, aluminum-albindin complexes are not detected in in- dividuals whose serum aluminum levels are normal (t200 nmol/l). However, sera of untreated hyper- aluminemic patients and sera from patients with either normal or elevated initial serum aluminum levels during therapy with desferrioxamine all con- tain aluminum-albindin complexes. These observations indicate that further investigation of the role of albindin in aluminum transport, in particular the fate of aluminum-albindin complexes, is necessary to understand mechanisms of aluminum toxicity and to develop appropriate therapies. Acknowledgements: Financial support from the Alsheimer Society of Peterborough and Victoria, Parke-Davis Inc. (Italy), the Scottish Rite Charitable Foundation of Canada, National Health and Welfare Canada and the Hunter Foundation is grate- fully acknowledged.

550

EFFECT OF DIFFERENT ALUMINUM COMPOUNDS ON THE OUTER MITDCHONDRIAL MEMBRANE CHANNEL,VDAC. aT.Mirzabekov, aC.Ballarin, aM.C.Soraato. bM.Nicotini and cP. Zatta. aDip. Chimica Biologica e Centro CNR di Fisiologia Mitooondriale, Universita’ di Padova(ltaiy),bDip. Scienze FarmaceuticheUniversita di Padova (Italy), CCentro CNR Emocianine-metalloproteine, Padova (Italy).

The voltage-dependent anion channel (VDAC) is the most abundant protein in the outer membrane of mitochondria (OMM) where it selves as the major permeability pathway. When studied in planar bilayers(in symmetrical 1 M KCI). this channel displays a high conductance(of approx. 4.0 nS) at low values of the membrane potential, whereas, upon increasing of voltage, it closes to several subconducting states. Given the possible neurotoxicological action of aluminum(Al), we have studied the effect of two different AI(III) compounds, AICl3 and aluminum lactate (AlLaoQ), on the detergent-free OMM isolated from rat brain and inserted in planar bilayer (in symmetrical 1 M KCI. pH 7.2). The experimental conditions used were such that one channel was present in the bilayer, this permitting to follow the behaviour of a single VDAC molecule. The resutts obtained showed that there was a dramatic effect on the channel electrical characteristics when the imposed voltage was positive, relative to the side where AI(III) was added. In fact, at either 1OOpM AICl3 or 10 uM AILact3, imposition of 20-30 mV reduced the conductance of the channel to approximately 50%. Moreover, there was also an increase in the rapkf open-close transitions. At negative voltages, but only prior to imposition of positive potentials, the channel had the tendency to remaining in the open state. Though our experimental conditions have allowed a better definition of the aluminum effect, the results resemble closely those found by Dill et al.[l] in multiVDAC-containing bilayer. In our work the AI(III) species responsible for the action on VDAC seems to be AI(OH)4-. As it appears, at pH 7.2 the concentration of AI(OH)4- is vanishing small so to render this species extremely effective on biological targets. Remarkably, the change in VDAC behavlour provoked by AI(III) remained despite the washing out operation and thus pointing to an apparently irreversible binding with, and alteration of, VDAC protein. Additionally, we found that AI(III) increased the stability of pure phospholiptd bilayer, and hence that it stably interacted also with the polar phospholipid headgroups[2]. 1) Dill et al. (1987) JMembr. Biol. 99: 187-196 2)Corain B, Nicolini M. Zatta P. (1992)Coord. Chem. Rev. lj_2: 33-54.

ANIMAL AND CELLULAR MODELS

391 MOLECULAR GENETIC STUDIES OF PRION DISEASES AND TRANSGENIC MOUSE MODELS OF CNB DEGENERATttX Stanley B. Prusiner. Departments of Neurology and of Biochemistry and Biophysics, University of California, San Francisco, CA 94143, USA.

Many studies of the infectious pathogens causing scrapie and other transmissi- ble neurodegenerative diseases support the hypothesis that these pathogens are novel and different from both viroids and viruses. After convincing evidence was obtained showing that scrapie infectivity depends upon a protein component, the term “prion” was introduced to distinguish these infectious pathogens from others including viroids and viruses, Enriching fractions from Syrian hamster (SHa) brain for scrapie prion infectivity led to the discovery of the prion pro- tein (PrP). Prion diseases include scrapie of sheep, bovine spongiform encephalopathy of cattle, as well as Creutzleldt-Jakob disease (CJD) and Ger- stmann-Straussler-Scheinker syndrome (GSS) of humans. Transgenic (Tg) mice expressing both SHa and mouse (MO) PrP genes were used to probe the molecular basis of the species barrier and the mechanism of scrapie prion rep- lication. Bioassays of brain extracts from two scrapieinlected Tg lines showed that the prion inoculum dictates which prions are synthesized de nova. even though the cells express both PrP genes. Our results argue that the species barrier for scrapie prions resides in the primary structure of PrP and forma- tion of infectious prions is initiated by a species-specific interaction between PrPSc in the inoculum and homologous PrPC. Diswvery of mutations in the PrP gene from humans with GSS and familial CJD established that prion diseas- es are unique among human illnesses - they are both genetic and infectious. Tg mice expressing MoPrP with the GSS point mutation spontaneously develop neurologic dysfunction, spongiform degeneration and astrocytic gliosis. Inocu- lation of brain extracts prepared from these Tg(GSSMoPrP) mice into Syrian hamsters and Tg mice expressing wild-type PrP transgenes has produced neu- rodegeneration in recipient animals after prolonged incubation times, If wn- vincing data on serial passage of prions from the inoculated recipients can bs obtained. then these results will argue that prions are devoid of foreign nucleic acid. Although it seems likely that transmissible prions are composed only of PrPSc molecules, a hypothetical second component such as a small polynucleo- tide remains a formal possibility. Studies on the structure of PrPSC and PrPc have been unsuccessful in defining a posttranslational chemical modification that distinguishes one PrP isoform from the other. These findings suggest that the difference between PrPSC and PrPC may be conformational. Whether distinct prion isolates or “strains” with different properties result from mul- tiple conformers of PrPSc remains to be established,