Risk-neutral (RN) and real-world (RW) densities are derived from option prices and risk assumptions, and are compared with densities obtained from historical time series. Two parametric methods that adjust from RN to RW densities are investigated, firstly a CRRA risk aversion transformation and secondly a statistical calibration.Both risk transformations are estimated using likelihood techniques, for two flexible but tractable density families. Results for the FTSE-100 index show that densities derived from option prices have more explanatory power than historical time series.Furthermore, the pricing kernel between RN & RW densities may be more regular than previously reported and a more reasonable risk aversion function is estimated.

The aim of this study was to examine the comprehensive neuroprotective mechanism of ligustrazine, which is extracted from Ligusticum Chuanxiong Hort., against vascular dementia (VD) in rats and apoptosis in oxygen and glucose deprivation (OGD) PC12 cells. Rats were subjected to bilateral common carotid artery occlusion (BCCAO) surgery and administered ligustrazine intragastrically for 6 weeks. At the end of the experiments, the hippocampal biomarkers brain-derived neurotrophic factor (BDNF), monocyte chemotactic protein 1 (MCP-1), and homocysteine (Hcy) were examined. In experiments in vitro, OGD PC12 cells were treated with ligustrazine for 0.5, 1, 3, 6, 12, or 24 h. The cell-released biomarkers BDNF, MCP-1, and Hcy were examined. Microscopy, acridine orange-ethidium bromide (AO/ EB) staining, and flow cytometry assays were performed to investigate apoptosis. Cleaved caspase-3, Bcl-2 associated X protein (Bax), and B cell lymphoma 2 (Bcl-2) expression was examined using Western blot assays. The results showed that biomarkers, including MCP-1 and Hcy, were significantly increased in both the in vivo and in vitro models, while the BDNF level was significantly decreased compared with the sham or vehicle models. Microscopy, AO/EB staining, and flow cytometry analysis showed that severe cell damage occurred in OGD PC12 cells, and apoptosis played a major role in this environment. Further Western blot studies showed that the apoptosis-related Bax/Bcl-2 protein ratio and cleaved caspase-3 were significantly increased in the experiment. However, ligustrazine profoundly suppressed the imbalance of these biomarkers, reduced cell damage, decreased the Bax/Bcl-2, and downregulated cleaved caspase-3. Pro-and anti-apoptotic biomarkers of multiple pathways including BDNF, MCP-1, and Hcy played a joint role in triggering the activation of the mitochondria-related Bax/Bcl-2 and caspase-3 apoptosis pathway in VD. Ligustrazine attenuated VD by comprehensively regulating BDNF, MCP-1, and Hcy and inactivating the Bax/Bcl-2 and caspase-3 apoptosis pathway. Our data provide novel insight into ligustrazine, which is a promising neuroprotective agent for VD disease treatment strategies.

Clivorine is a representative naturally occurring hepatotoxic otonecine-type pyrrolizidine alkaloid. Our previous study has demonstrated that clivorine induces liver damage via metabolic activation to form the reactive pyrrolic ester followed by covalent binding to liver tissue constituents. The present study investigated species differences in the in vitro metabolic activation of clivorine in the male rat and guinea pig of both sexes. In the male rat, the activation of clivorine to form the reactive pyrrolic ester was found as the only metabolic pathway. Moreover, the toxic tissue-bound pyrroles and four isolatable metabolites identified, namely DHR, 7-GSH-DHR, 7,9-diGSH-DHR, and clivoric acid, were all generated from further metabolism of this reactive intermediate. In the case of both sexes of guinea pig, the same activation was observed as the minor biotransformation, while an additional metabolic pathway, a direct hydrolysis of clivorine to form novel clivopic acid was identified as the predominant detoxification pathway. Furthermore, the formation rates for the toxic tissue-bound pyrroles and less toxic DHR were significantly slower and higher, respectively, compared with those in the male rat. In addition, the formation of the reactive pyrrolic ester was mediated by the CYP3A subfamily in both animals, while carboxylesterases might be responsible for the detoxification hydrolysis in guinea pig. The results suggest that the higher metabolic rates for detoxification hydrolyses and the lower formation rate for the toxic tissue-bound pyrroles play the key roles in guinea pig resistance to clivorine intoxication. Therefore, the male rat and guinea pig should be the suitable animal models for further studies of bioactivation and deactivation of otonecine-type PA, respectively.

The gender differences in the in vitro microsomal metabolic activation of hepatotoxic clivorine, a representative naturally occurring hepatotoxic otonecine type pyrrolizidine alkaloid, in Sprague-Dawley rats and their relation to the gender differences in susceptibility to clivorine intoxication were reported in the present study. Clivorine-induced liver damage in the male rat via metabolic activation to form the reactive pyrrolic ester followed by covalent binding to liver tissue constituents has been reported previously by our research group. The present study demonstrated, for the first time, that cytochromes p450 3A1 and 3A2, which are constitutively expressed in the male rat, might play a significant role in the metabolic activation of clivorine in the rat. Thus, in the male rat, the metabolic activation by liver microsomes to form the reactive pyrrolic ester was found as the only direct metabolic pathway of clivorine followed by subsequent formation of the toxic tissue-bound pyrroles leading to hepatotoxicity. In the case of the female rat, a less significant metabolic activation was observed, whereas the formations of two novel nonpyrrolic metabolites were determined as the predominant biotransformations. None of the four cDNA-expressed rat enzymes (cytochrome p450 2C12, 2E1, 3A1, 3A2) tested could catalyze the formation of these two new metabolites. Furthermore, the female rat (LD(50) = 114 +/- 9 mg/kg, i.p.) was found to be significantly less susceptible to clivorine intoxication than the male rat (LD(50) = 91 +/- 3 mg/kg, i.p.). Therefore, the results suggested that a significantly lower metabolic activation due to the lack of cytochrome p450 3A1 and p450 3A2 activities mainly accounted for the smaller susceptibility of the female rat to clivorine intoxication.