The K16ApoE peptide has been demonstrated to deliver a supraphysiological level of protein therapeutics to the brain and further increase the life-span of mice with a lysosomal storage disorder (LSD). If successfully developed, K16ApoE would provide new treatments for LSD and many other neurological diseases. However, while the K16ApoE can cross the blood-brain barrier, data indicates a toxic response associated with it. The mechanism of toxicity must be resolved for further clinical translation. The toxic response towards the peptide was hypothesized to be induced by inhibition of acetylcholinesterase (AChE) activity at neuro-muscular junction. Here, the dose-response analysis between AChE and K16ApoE was conducted in both female and male mice. Results demonstrated that AChE activity was significantly reduced with increasing dose of K16ApoE except for the mid-dose where a dramatic increase in AChE activity was observed. Also, obvious difference in response to K16ApoE was shown when considering the influence from sex and body weight. Though the statistical analysis of the dose response and survival ratio suggested that AChE is not the primary mechanism of action for the acute toxicity of K16ApoE, the complex inhibition/stimulation response of AChE indicated that this enzyme must play a role in the toxicity of the peptide.
Ge-132 was administered to both sexes of F344 rats at dietary levels of 0, 0.6, 1.3, and 2.5% for 2 years. There were no adverse effects on survival rate, food consumption or hematology data, although diarrhea and body-weight retardation were observed in the male and female 2.5% groups. Significant increases of kidney and adrenal weights were noted in both male and female 2.5% group. Macroscopically, dilatation of the cecum was observed in both male and female 2.5% group, and enlargement of the adrenals was observed in the male of 2.5% group. Significantly higher incidences of benign or malignant pheochromocytoma were observed in the male 1.3% group and both male and female 2.5% groups. Significantly positive trends were noted in the incidences of kidney pelvic and papilla mineralization in both sexes and cortico-medullary junction in females. To investigate possible mechanisms underlying Ge-132-associated development of pheochromocytoma, male F344 rats were administered diets containing 0, 0.6, or 2.5% Ge-132 for 4 or 13 weeks. Although loose stools and increasing water consumption were observed in treated groups, there were no body-weight retardation. Significant elevation of inorganic phosphorus in the serum was found in the 2.5% group at week 13. Dilatation of the cecum and increased cecum weight were evident macroscopically in the 2.5% group. Significant elevation of Ki-67 positive ratio in adrenal medullary cells was also found in the 2.5% group. These data indicated that Ge-132 ingestion induced disturbance in calcium/phosphorus homeostasis, and secondarily induced the development of benign or malignant pheochromocytoma in rats. Such secondary pheochromocytomas are considered to be not relevant for human risk assessment.
Rabbits are commonly used as laboratory animals in ocular toxicity studies. During development of ophthalmic drugs and medical devices, knowledge regarding sex differences of ocular anatomy and histology is important in the interpretation of toxicity data. However, limited information is available regarding ocular sex differences in rabbit eyes. Information on sex differences of rabbit eyes supports the justification of using single sex in the design of toxicity studies. We therefore investigated anatomical and histological ocular sex differences in Dutch belted rabbits aged 6 to 20 weeks which are frequently used in toxicity studies. Anatomical parameters of the eyeball (axial length, diameter, weight, volume), cornea (height, diameter), lens (thickness, diameter, weight, volume), and vitreous humor (weight, volume) were measured. Paraffin blocks of eye, meibomian glands, and lacrimal glands from males and females were sectioned and stained using hematoxylin and eosin, and compared. As the results, the anatomical parameters and their growth ratios showed no difference between males and females. In the histological comparison, although the development of glandular tissues was observed in both sexes according to aging, no sex differences were found. We concluded that there is no anatomical or histological sex differences in the eyes of Dutch belted rabbits from the period of post-weaning to sexual maturation.