Characterization of changes in global gene expression in the hearts and kidneys of transgenic mice overexpressing human angiotensin-converting enzyme 2 / 한국실험동물학회지

Human angiotensin-converting enzyme 2 (hACE2) has recently received a great attention due to it play a critical role as SARS-CoV receptor in the infection of human body. However, no further analysis for gene regulation has been performed in target tissues of model mice during hACE2 overproduction. To characterize changes in global gene expression in the hearts and kidneys of rtTA/hACE2 double transgenic (dTg) mice in response to hACE2 overexpression, total RNA extracted from these tissues from dTg mice after doxycycline (Dox) treatment was hybridized to oligonucleotide microarrays. Briefly, dTg mice were generated by cross-mating pα-MHC/rtTA Tg mice with pTRE/hACE2 Tg mice. The expression level of hACE2 protein was determined to be high in hearts, kidneys, and brains of dTg mice, whereas lung, liver, and testis tissues expressed low levels. The level of hACE2 was significantly enhanced in hearts and kidneys of the Dox+dTg group compared to that in Vehicle+dTg mice although consistent levels of mouse ACE2 (mACE2) remained in the same tissues. Based on the microarray analysis of heart tissue, 385 genes were differentially expressed, including 168 upregulated and 217 downregulated, when comparing non-Tg and Vehicle+dTg mice, whereas 216 genes were differentially expressed, including 136 upregulated and 80 downregulated, between Vehicle+dTg and Dox+dTg mice. In the kidneys, 402 genes were differentially expressed, including 159 upregulated and 243 downregulated, between non-Tg and Vehicle+dTg mice. Dox-treated dTg mice exhibited the differential expression of 4735 genes including 1636 upregulated and 3109 downregulated. Taken together, these findings suggested that several functional groups and individual genes can be considered biomarkers that respond to hACE2 overexpression in dTg mice. Moreover, our results provided a lot of useful information to predict physiological responses when these dTg mice are applied as a susceptible model for novel coronavirus (SARS-CoV, COVID-19) in both vaccine and drug development.

Beneficial effect of diosgenin as a stimulator of NGF on the brain with neuronal damage induced by Aβ-42 accumulation and neurotoxicant injection / 한국실험동물학회지

To investigate the beneficial effects of diosgenin (DG) on the multiple types of brain damage induced by Aβ-42 peptides and neurotoxicants, alterations in the specific aspects of brain functions were measured in trimethyltin (TMT)-injected transgenic 2576 (TG) mice that had been pretreated with DG for 21 days. Multiple types of damage were successfully induced by Aβ-42 accumulation and TMT injection into the brains of TG mice. However, DG treatment significantly reduced the number of Aβ-stained plaques and dead cells in the granule cells layer of the dentate gyrus. Significant suppression of acetylcholinesterase (AChE) activity and Bax/Bcl-2 expression was also observed in the DG treated TG mice (TG+DG group) when compared with those of the vehicle (VC) treated TG mice (TG+VC group). Additionally, the concentration of nerve growth factor (NGF) was dramatically enhanced in TG+DG group, although it was lower in the TG+VC group than the non-transgenic (nTG) group. Furthermore, the decreased phosphorylation of downstream members in the TrkA high affinity receptor signaling pathway in the TG+VC group was significantly recovered in the TG+DG group. A similar pattern was observed in p75NTR expression and JNK phosphorylation in the NGF low affinity receptor signaling pathway. Moreover, superoxide dismutase (SOD) activity was enhanced in the TG+DG group, while the level of malondialdehyde (MDA), a marker of lipid peroxidation, was lower in the TG+DG group than the TG+VC group. These results suggest that DG could exert a wide range of beneficial activities for multiple types of brain damage through stimulation of NGF biosynthesis.

Monitoring of antibiotic resistance in bacteria isolated from laboratory animals / 한국실험동물학회지

The drug resistance of microorganisms isolated from laboratory animals never treated with antibiotics is being reported consistently, while the number of laboratory animals used in medicine, pharmacy, veterinary medicine, agriculture, nutrition, and environmental and health science has increased rapidly in Korea. Therefore, this study examined the development of antimicrobial resistance in bacteria isolated from laboratory animals bred in Korea. A total of 443 isolates (7 species) containing 5 Sphingomonas paucimobilis, 206 Escherichia coli, 60 Staphylococcus aureus, 15 Staphylococcus epidermidis, 77 Enterococcus faecalis, 27 Citrobacter freundii, 35 Acinetobacter baumannii were collected from the nose, intestine, bronchus and reproductive organs of ICR mice and SD rats. Of these species, Acinetobacter baumannii and Enterococcus faecalis showed significant antimicrobial resistance according to the minimum inhibition concentration (MIC) in E-test. In case of Acinetobacter baumannii, several isolates showed MIC values 16-128 microg/mL for cefazolin and cefoxitin, and higher resistance (128-512 microg/mL) to nitrofurantoin than that of standard type. Resistance to cefazolin, cefoxitin and nitrofurantoin was detected in 17.14, 20.00, and 8.57% of the Acinetobacter baumannii isolates, respectively. In addition, 44.1% of the Enterococcus faecalis isolates collected from the laboratory animals were resistant to oxacillin concentration of 16-32 microg/mL range, while MIC value of standard type was below oxacillin concentration of 6 microg/mL. These results suggest that in rodent species of laboratory animals, Acinetobacter baumannii are resistance to cefazolin, cefoxitin and nitrofurantoin, whereas those of Enterococcus faecalis were resistance to oxacillin.

Overexpression of Insulin Degrading Enzyme could Greatly Contribute to Insulin Down-regulation Induced by Short-Term Swimming Exercise / 한국실험동물학회지

Exercise training is highly correlated with the reduced glucose-stimulated insulin secretion (GSIS), although it enhanced insulin sensitivity, glucose uptake and glucose transporter expression to reduce severity of diabetic symptoms. This study investigated the impact of short-term swimming exercise on insulin regulation in the Goto-Kakizaki (GK) rat as a non-obese model of non-insulin-dependent diabetes mellitus. Wistar (W/S) and GK rats were trained 2 hours daily with the swimming exercise for 4 weeks, and then the changes in the metabolism of insulin and glucose were assessed. Body weight was markedly decreased in the exercised GK rats compare to their non-exercised counterpart, while W/S rats did not show any exercise-related changes. Glucose concentration was not changed by exercise, although impaired glucose tolerance was improved in GK rats 120 min after glucose injection. However, insulin concentration was decreased by swimming exercise as in the decrease of GSIS after running exercise. To identify the other cause for exercise-induced insulin down-regulation, the changes in the levels of key factors involved in insulin production (C-peptide) and clearance (insulin-degrading enzyme; IDE) were measured in W/S and GK rats. The C-peptide level was maintained while IDE expression increased markedly. Therefore, these results showed that insulin down-regulation induced by short-term swimming exercise likely attributes to enhanced insulin clearance via IDE over-expression than by altered insulin production.