Neurotoxicity of 1,3,5-Trinitrobenzene (TNB): Immunohistochemical Study of Cerebrovascular Permeability

Abstract

Abstract. 1,3,5-Trinitrobenzene (TNB) is a soil and water contaminant at certain military installations. Encephalopathy in rats given 10 daily oral doses of TNB has been reported. The lesion was bilaterally symmetric vacuolation and microcavitation in the cerebellar roof nuclei, vestibular nuclei, olivary nuclei, and inferior colliculi. The contribution of the blood-brain barrier (BBB) in the genesis of these lesions remains uncertain. One of the main goals of the present work was to evaluate the functional state of the BBB. Male Fischer 344 rats (five rats/group) were euthanatized after four, five, six, seven, eight, or 10 daily doses of TNB (71 mg/kg). A different set of rats (five rats/group) was allowed to recover for 10 or 30 days after receiving 10 doses of TNB. Integrity of the BBB was assessed by immunohistochemical staining for extravasated plasma albumin on paraffin-embedded sections. Rats euthanatized after four to eight doses had no lesions, and albumin extravasation in the susceptible regions of the brain was minimal. Rats receiving 10 daily doses of TNB had bilaterally symmetric vacuolation and microcavitation in the cerebellar nuclei, vestibular nuclei, and inferior colliculi in association with multifocal, often confluent foci of extravasated albumin in susceptible nuclei. Albumin was present in vascular walls, extracellular space, and neurons. Immunoreactivity in neurons was of two types: cytoplasmic staining representing pinocytic uptake and homogenous staining of the entire neuron (nucleus and cytoplasm) due to uncontrolled albumin leakage through the damaged cell membrane. In rats allowed to recover for 10 days, the microcavitated foci were infiltrated by glial and gitter cells. Albumin immunoreactivity was present as extracellular granular debris, and neuronal staining (for albumin) was mild. In rats allowed to recover for 30 days, immunoreactivity to albumin was not seen. This study demonstrates that TNB-mediated tissue damage is accompanied by breakdown of the BBB. The presence of vacuolation and associated extravasated serum proteins in TNB-treated rats is an indication of vasogenic brain edema, which appears to be a critical event in TNB toxicity. Additional studies are needed to determine the reason for selective regional vulnerability and brain microvasculature susceptibility to TNB.

Neurotoxicology of the Brain Barrier System: New Implications

“…Prior to the tissue lesion, however, TNB breaks down the BBB and allows large serum proteins to diffuse through it. Thus, the selective regional vulnerability of brain capillaries to TNB has been suggested as a critical event in TNB-mediated neurotoxicity (5). Other nitrobenzene derivatives such as m-dinitrobenzene share similar toxic mechanisms by provoking oxidative cytotoxicity of the BBB, followed by neuronal and neuroglial injury (6).…”

Wildlife Toxicity Assessment for 1,3,5-Trinitrobenzene (TNB)

“…Immunohistochemical staining of excised brains was used to evaluate the integrity of the blood-brain barrier in F344 rats challenged with TNB [22]. Five male F344 rats/group were gavaged with TNB in corn oil at 71 mg/kg for 4, 5, 6, 7, 8, or 10 days with 1 dose per day.…”

Effects of 1,3,5-Trinitrobenzene on Cytotoxicity and Metabolic Activity of Type I Astrocytes of Rats

“…TNB is a soil and water contaminant at installations that are currently or have been involved in the manufacture of explosives. Previous studies in Fischer-344 rats receiving single daily oral doses of trinitrobenzene over 6 to 10 days have resulted in methemoglobinemia, hemolytic anemia, testicular atrophy, and neurologic pathology (Chandra 1995;Chandra, Qualls, and Reddy 1995a;Chandra et al 1997a;Chandra, Qualls, and Reddy 1997b;Chandra et al 1999). Ataxia progressing to recumbence is a manifestation of the neurologic abnormalities.…”

“…The mechanisms by which TNB exerts its toxic action on the central nervous system (CNS) are unclear, but previous investigators have shown that TNB-mediated tissue damage is accompanied by breakdown of the blood-brain barrier (BBB) with extravasation of albumin (Chandra et al 1999). Astrocytes contribute to the maintenance and induction of the BBB characteristics in the brain endothelium, including tightness of tight junctions (Stewart and Wiley 1981; Butt, Jones, and Abbott 1990; Rubin et al 1991).…”

“…The presence of vacuolation and associated extravasated serum proteins is an indication of vasogenic brain edema, which appears to be a critical event in TNB toxicity. The lesions appear primarily glial and vascular in origin, with secondary neuronal involvement (Chandra et al 1995b(Chandra et al , 1999.…”