A class of imidazolium salts (IMSs) is routinely used in organic synthetic chemistry as precursors to generate N-heterocyclic carbenes (NHCs) with catalytic activity. However, their biological properties are largely unknown. The current study investigates the biological activity of a typical NHC precursor DBZIM and its trimer TDBZIM in hepatic stellate cells (HSCs), which is an in vitro model for studying liver fibrosis. The results show that HSCs treated with IMSs have an enhanced GSH/GSSG ratio and a reduced level of reactive oxygen species (ROS), which may consequently contribute to the attenuation in gene expression of fibrogenic molecules such as smooth muscle actin-alpha (SMAA), transforming growth factor-beta 1 (TGF-beta1), procollagen alphaI(I) and fibronectin. Further, the in vivo experiments demonstrate that DBZIM is an anti-fibrotic agent in a mouse model of liver fibrosis. These findings suggest that the versatile IMSs could be a potential source for developing novel therapeutics to treat liver fibrosis and other fibrogenic disorders caused by oxidative stress and TGF-beta1 mal-signalling.

The current real-time fluorescent imaging method described here is a powerful preclinical tool to directly monitor retinal gliosis caused by various retinopathies. In addition, this molecular imaging method should be useful in assessing retinal neurotoxicity and in therapeutic development in a preclinical setting.

We have recently identified a class of imidazolium salts (IMSs) with antioxidative property and can function as scavengers for radical oxygen species (ROS) [18]. Here, we investigate one of the IMSs, 1,3-bisbenzylimidazolium bromide (DBZIM), for its possible role in attenuating neurotoxicity and gliosis in the retina and the brain induced by a Parkinsonian neurtoxicant, methyl-4(2'-methylphenyl)-1,2,3,6-tetrahydropyridine (2'-CH(3) -MPTP), which is a free radical generating agent. In this study, we employ a molecular retinal imaging method, which we recently developed in a transgenic mouse model expressing green fluorescent protein (GFP) under the control of glial fibrillary acidic protein (GFAP) promoter [14], to assess the efficacy of DBZIM, since currently no in vitro system with a sufficient complexity is available for accurately assessing a compound's efficacy. The longitudinal imaging results showed DBZIM can effectively suppress the neurotoxicant-induced retinal gliosis. Immunohistochemistry performed on the postmodern mouse brain confirmed that DBZIM also reduced striatal gliosis, and concomitantly attenuated the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). These findings suggest that DBZIM could be a useful small molecular compound for studying neurotoxicity and neuroprotection in the retina and the brain.

We previously reported that a single subcutaneous (s.c.) injection of the neurotoxicant, 1-methyl-4-(2'-methylphenyl)-1,2,3,6-tetrahydropyridine or 2'-CH(3)-MPTP, to postnatal day 4 (PD4) mice caused acute and transient gliosis in the brain, which can be noninvasively monitored during a course of 8 h immediately after the dosing [Ho, G., Zhang, C.Y., Zhuo, L., 2007. Non-invasive fluorescent imaging of gliosis in transgenic mice for profiling developmental neurotoxicity. Toxicol. Appl. Pharmacol. 221, 76-85]. In the current study, we examined the consequence of PD4 mice receiving multiple injections (4 x 8 mg/kg, s.c. in 2 h intervals) of the same neurotoxicant 24-72 h after the last injection. Here we showed that the multiple dosing scheme (with a higher cumulative dose) triggered a severe gliosis not only in the striatum and substantia nigra pars compacta (SNpc), but also in hippocampus and cerebellum when examined by noninvasive in vivo imaging and by immunohistochemistry (IHC), respectively, in the PD5 to PD7 mice. When neonates treated with the neurotoxicant at PD4 were allowed to develop to 10 weeks of age and examined with IHC, a majority of the dopaminergic (DA) neurons were found to be permanently depleted from the adult SNpc. Our findings suggest that neurotoxicant-elicited neonatal gliosis can be used as an early molecular signature to predict the permanent loss of DA neurons in the developed brain. Since 2'-CH(3)-MPTP is an inducer of Parkinsonism in mice, the molecular imaging method described here is a relatively simple and powerful tool for longitudinally studying the developmental aspect of Parkinsonism.