Molecular and genetic aspects of toxicant-induced apoptosis in the male germ line

Workshop 6. The Gulf WarIllness and the Exposure to Anticholinesterases propriate activation of proapoptotic signals is likely the mechanism underlying genotoxicant-induced female germ cell loss.

IW5/L4! MOLECULAR AND GENETIC ASPECTS OF TOXICANTINDUCED APOPTOSIS IN THE MALEGERMLINE

1. Lee, 1.H. Richburg, G. Li, K. Boekelheide *. Brown University,

Providence, RI, USA Testicular germ cell apoptosis is a normal physiologic mechanism used to regulate spermatogenesis. Massive germ cell apoptosis is the usual consequence of various insults which disrupt testicular homeostasis, including toxicant exposure. Recently, the Fas system was identified as a key regulator of germ cell apoptosis [Endocrinology 138: 2081-2088, 1997]. FasL, produced by Sertoli cells, binds the Fas receptor on germ cells and activates the apoptotic sequence. Exposure of rats to Sertoli cell toxicants, such as mono-(2-ethylhexyl) phthalate [MEHP] and 2,5-hexanedione [2,5-HD], resulted in an initial upregulation of FasL expression prior to an upregulation of Fas associated with massive germ cell apoptosis. On the other hand, exposure of rats to radiation, a germ cell toxicant, resulted in an upregulation of Fas expression without increasing FasL. In model systems, FasL binding triggers the formation of a Fas-associating complex containing positive and negative effectors of apoptosis, such as Fas associating protein with novel death domain [FADD], receptor interacting protein [RIP], and Fas-associated phosphatase-l [Fap-l]. Formation of the Fas-associating complex leads to direct and rapid activation of the caspases, important executioners of the apoptotic process. Exposure of rats to MEHP resulted in increased testicular expression of RIP and Fap-l , and activation of the caspase cascade in the dying cells. Furthermore, small peptide inhibitors of the caspases, like YVAD-crnk, protected against toxicant-induced testicular germ cell apotposis. Taken together, these results identify the Fas system as an important paracrine mediator of testicular germ cell apoptosis.

W6. TheGulfWar Dlness and the Exposure to Anticholinesterases

IW6/L1 I

EXPERIMENTAL AND CLINICAL TOXICOLOGY OF ANTICHOLINESTERASE AGENTS

A. Moretto. Istituto di Medicina del Lavoro, Universita degli Studi di Padova, Padova, Italy Several organophosphorus compounds (OP) and carbamates (CA) are used as insecticides or warfare agents (OPs only). Their toxic effect in the central and peripheral nervous system is due to inhibition of acetyl-cholinesterase (AChE) at nerve endings which causes accumulation of acetylcholine (ACh) and consequently overstimulation of the nicotinic and muscarinic receptors. The cholinergic syndrome appears at about 50% AChE inhibition whereas death is believed to occur at >90% AChE inhibition. Inhibition of AChE (phosphorylation) by most OPs is irreversible whereas CAs reversibly inhibit AChE which spontaneously reactivates with tIl2 of minutes; dimethylphosphorylated AChE partially and slowly (tIl2 of 1-2 hours) reactivates. Although, long-term mild neurobehavioural changes of questionable significance have been reported in some instances, recovery from the cholinergic syndrome appears to be complete, unless lesions develop in the central nervous system as a consequence of either convulsions or anoxia. Certain OPs and CAs have been reported to interact with cholinergic receptors in vitro. The toxicological relevance of these interactions has not yet been clarified, although it might be possible that toxic effects arise from direct stimulation or inhibition of the effector organ or nerve. Certain OPs cause the so called OP induced delayed polyneuropathy (OPIDP) which develops 2-5 weeks after an acute poisoning. The

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molecular target is believed to be neuropathy target esterase (NTE). OP insecticides are more potent AChE rather than NTE inhibitors and therefore the dose required to cause OPIDP is much higher than that causing the cholinergic syndrome. In the experimental animal, OPIDP is associated with > 70% NTE inhibition both after single or repeated exposures. The threshold in man is not known, although there are indications that it is not very different. Some non-neuropathic esterase inhibitors (OPs, CAs, sulfonyl fluorides) exacerbate the clinical outcome of OPIDP and other chemical axonopathies, and of nerve crush. The phenomenon has been called promotion and has so far been observed in experimental animals only. Its moleculat target has yet to be identified although it shares some characteristics withNTE.

IW6/L21

HEALTH EFFECTS OF EXPOSURES IN THE GULF WAR

P.S. Spencer. PortlandEnvironmental HazardsResearch Center, a joint project ofthe DepartmentofVeterans Affairs (DVA)Medical Center and Centerfor Researchon Occupational & Environmental Toxicology ofOregonHealth Sciences University, Portland, OR, USA Coalition forces serving in S.w. Asia during the Persian Gulf War (PGW) were exposed to arrays of physical, physiological, psychological, biological, and chemical factors that played unknown individual and collective roles in the development of unexpected, unexplained illness among troops of most but not all participating nations. PGW Unexplained Illness (PGWUI) is a variable constellation of symptoms (cognitive complaints, persistent fatigue and muscle-joint pain, among others) with no known objective signs. Testing for associations between PGWUI and exposures is challenging. Classical approaches to exposure evaluation are compromised by a paucity of hard data and consequent dependence on self-reported information with restricted validity. Less imperfect than many other non-classical approaches is one that assesses associations between illness and period of deployment; (1) those troops who were deployed to S.w. Asia prior to combat and who had left the region by 1991 had potential exposure arrays that were distinct both from those (2) who were deployed for the first three months of 1991, during which combat took place, and from those (3) who served in the period immediately thereafter. How PGWUI, and individual symptoms thereof, associate with the three distinct deployment periods indicates which exposure sets have etiological significance. Further insight is obtained by analyzing how symptoms and exposures compare across deployment groups. [U.S. DVA-funded]

IW6/L31 EPIDEMIOLOGIC ASSOCIATION IN US VETERANS BETWEEN GULF WAR ILLNESS AND EXPOSURE TO ANTICHOLINESTERASES

T. Kurt. Univ. TexasSouthwestern, 3645 StratfordAvenue, Dallas (Texas), USA To investigate complaints of Gulf War veterans, epidemiologic and case-control and animal modeling studies were performed. Looking for OPIDP variants, our epidemiologic project studied 249 Naval Reserve construction batallion (CB24) men. Extensive surveys were drawn for symptoms and exposures. An existing test (PAl) was used for neuropsychologic. Using FACTOR, LOGISTIC and FREQ in 6.07 SAS, symptom clusters were sought with high eigenvalues from orthogonically rotated 2-stage factor analysis. After factor loadings and Kaiser measure for sampling adequacy (0.82), 3 major and 3 minor symptom clusters were identified. Internally consistent by Cronbach's coefficient, these were labeled syndromes: #1 impaired cognition, #2 confusion-ataxia, #3 arthro-myo-neuropathy, #4 phobia-apraxia, #5 fever-adenopathy and #6 weakness-inconti-