Acetylcholinesterase Protein Levels Research Articles

Blood and Bronchoalveolar Lavage Fluid Acetylcholinesterase Levels Following Microinstillation Inhalation Exposure to Sarin in Guinea Pigs

We determined acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition in the bronchoalveolar lavage fluid (BALF) following inhalation exposure to chemical threat nerve agent (CTNA) sarin. Age- and weight-matched male guinea pigs were exposed to five different doses of sarin (169.3, 338.7, 508, 677.4, and 846.5 mg/m3) using a microinstillation inhalation exposure technique for 4 min. The technique involves aerosolization of the agent in the trachea using a microcatheter with a center hole that delivers the agent and multiple peripheral holes that pumps air to aerosolize the agent at the tip. Animals exposed to higher doses of sarin occasionally developed seizures and succumbed to death within 15 min after exposure. The LCt50 for sarin using the microinstillation technique was determined to be close to 677.4 mg/m3. Ear blood AChE activity showed a dose-dependent inhibition at 15 min postexposure. The inhibition of blood AChE remained constant over 35 and 55 min after sarin exposure indicating that there was no lung depot effect. Cardiac blood AChE and butyrylcholinesterase (BChE) activity in surviving animals euthanized at 24 h postexposure showed a dose-dependent inhibition with an inhibition of 60% at 677.4 and 846.5 mg/m3 sarin exposure. AChE and BChE activity in bronchoalveolar lavage fluid (BALF) showed a slight increase at 338.7 to 677.4 mg/m3 sarin exposure but a marginal inhibition at 169.3 mg/m3. In contrast, the AChE protein levels determined by immunoblotting showed an increase at 169.3 mg/m3 in the BALF. The BALF protein level, a biomarker of lung injury, was increased maximally at 338.7 mg/m3 and that increase was dropped with an increase in the dose of sarin. The BALF protein levels correlated with the AChE and BChE activity. These data suggest that sarin microinstillation inhalation exposure results in respiratory toxicity and lung injury characterized by changes in lavage AChE, BChE, and protein levels.

Anticholinesterase treatment of chicken retinal cells increases acetylcholinesterase protein independently of protein kinase C

It has been reported that anticholinesterase exposure, e.g. by environmental toxins or nerve gases, can increase acetylcholinesterase (AChE) protein , possibly as an autoregulatory stress response. We earlier have transfected retinal cells of the chick embryo with a pSVK3-AChE rab-cDNA vector to heterologously express rabbit AChE, which concomitantly also increased AChE protein from chick. To analyse further the cell-internal pathways of these different paradigms (anticholinesterase treatment vs. AChE transfection) which both lead to an AChE increase, we here show that AChE overexpression by transfection leads to an increase in protein kinase C (PKC). Most remarkably, when cells independently of, or in addition to their transfection are treated with 10 μM of the AChE inhibitor BW284c51, AChE protein levels are much more dramatically increased up to 20-fold. This treatment, however, does not affect PKC. These data show that (i) retinal cells respond to anticholinesterase insult by a massive increase of AChE protein; (ii) the response to BW284c51 is not PKC-mediated; and (iii) both strategies of AChE increase follow different cell-internal pathways, their effects being additive. The ecological and biomedical implications of these findings are briefly discussed.

Pigmented epithelium sustains cell proliferation and decreases expression of opsins and acetylcholinesterase in reaggregated chicken retinospheroids.

We investigated the effect of the retinal pigmented epithelium on cell proliferation and differentiation in rosetted retinospheroids, which are retina-like spheres reaggregated in the complete absence of retinal pigmented epithelium from dissociated retinal cells of 6-day-old chick embryos in a rotation culture system. In spheroids raised in the absence of retinal pigmented epithelium (controls), acetylcholinesterase was expressed in cells of an inner nuclear-like layer and their neuropil matrices. Moreover, the ratio between rods and cones was found to be approximately normal throughout the spheroid. When spheroids were cultured in the presence of retinal pigmented epithelium monolayers, cell proliferation in spheroids as determined by BrdU labelling was significantly increased and extended for 1 week, while acetylcholinesterase protein levels and specific activities in homogenates were decreased to approximately 30%. At the same time, opsin immunoreactivity was completely suppressed within the spheroid and appeared slowly in cells around its periphery; i.e. the proportion of rhodopsin-positive cells decreased from 14 to 3%. This study reveals that the retinal pigmented epithelium in vitro sustains cell proliferation but inhibits the differentiation of acetylcholinesterase-positive cells and of photoreceptors.