Roles of fibrinolytic system components in the nervous system

Pharmacokinetics and tissue distribution of a novel marine fibrinolytic compound in Wistar rat following intravenous administrations

We investigated a novel marine fibrinolytic compound for use in thrombolytic therapy. Pharmacokinetics and the tissue distribution of this novel marine fibrinolytic compound, FGFC1(2) (fungi fibrinolytic compound 1), were investigated in Wistar rats after intravenous (IV) bolus administration of two concentrations (10 and 20mg/kg). Plasma FGFC1 and tissue extracts were measured using HPLC with UV detection. FGFC1 was detected using a C18 column with a gradient eluted mobile phase of acetonitrile-water (0.1% trifluoroacetic acid), 1.0mL/min. Chromatograms were monitored at 265nm (column temperature: 40°C). Pharmacokinetic data indicate that FGFC1 fitted well to a two-compartment model. Elimination half-lives (t1/2) of FGFC1 were 21.51±2.17 and 23.22±2.11min for 10 and 20mg/kg, respectively. AUC0-t were 412.19±19.09, 899.09±35.86μg/mLmin, systemic clearance (CL) was 0.023±0.002, 0.022±0.002 ((mg/kg)/(μg/mL)/min) and the mean residence time (MRT) was 10.15±0.97, 9.65±1.40min at 10 and 20mg/kg, respectively. No significant differences were observed in the systemic clearance and mean residence time at the tested doses, suggesting linear pharmacokinetics in rats. Tissue distribution data reveal that FGFC1 distributed rapidly in most tissues except the brain and that the highest concentration of the drug was in the liver. In the small intestine, FGFC1 initially increased and then declined, but remained comparatively high 60min after administration, suggesting that enterohepatic circulation may exist.

Tissue plasminogen activator deficiency promotes early phase regeneration in the olfactory epithelium after bulbectomy

BACKGROUND

Tissue type plasminogen activator (tPA) functions as a fibrinolytic factor in the blood and has unique roles in the nervous system. However, the role of tPA in the olfactory epithelium (OE) is still unclear. Generally, surgical ablation of the olfactory bulb (bulbectomy) triggers degeneration followed by regeneration of OE. In this experimental study, we investigated the role of tPA in OE regeneration.

METHODS

Wild-type (WT) mice and tPA-knockout (tPA(-/-) ) mice were subjected to bulbectomy. Reverse-transcription polymerase chain reaction (RT-PCR), in situ hybridization, and immunohistochemical examination was done to detect tPA expression in the olfactory bulb and OE. Cellular proliferation and apoptosis was also monitored in the OE.

RESULTS

Before bulbectomy, tPA was found to be expressed in the olfactory bulb and OE. OE degenerated to a similar extent in both strains between 0 and 3 days after bulbectomy. However, OE was thicker and contained more cells in tPA(-/-) mice than in WT mice at 7 days after bulbectomy. Moreover, the number of apoptotic bodies was reduced and the number of proliferating cells was increased in the OE of tPA(-/-) mice compared to WT mice, after bulbectomy. Transmission electron microscopy revealed continuous degeneration of the OE for up to 7 days after bulbectomy in WT mice. In contrast, we observed some intact olfactory vesicles and almost normal supporting cells in the OE of tPA(-/-) mice, at 7 days after bulbectomy.

CONCLUSION

The current findings show that the tPA-plasmin system plays an inhibitory role in the regulation of regeneration in the OE.

Morphological assessment of the luminal surface of olfactory epithelium in mice deficient in tissue plasminogen activator following bulbectomy

OBJECTIVE

This study aimed to investigate the function of tissue plasminogen activator in the olfactory epithelium of mice following neural injury.

METHOD

Transmission electron microscopy was used to study the changes in the morphology of the olfactory epithelium 1-7 days after surgical ablation of the olfactory bulb (bulbectomy).

RESULTS

Prior to bulbectomy, a uniformly fine material was observed within some regions of the olfactory epithelium of mice deficient in tissue plasminogen activator. At 2-3 days after bulbectomy, there were degenerative changes in the olfactory epithelium. At 5-7 days after bulbectomy, we noted drastic differences in olfactory epithelium morphology between mice deficient in tissue plasminogen activator and wild-type mice (comparisons were made using findings from a previous study). The microvilli seemed to be normal and olfactory vesicles and receptor neuron dendrites were largely intact in the olfactory epithelium of mice deficient in tissue plasminogen activator.

CONCLUSION

The tissue plasminogen activator plasmin system may inhibit the regeneration of the olfactory epithelium in the early stages following neural injury.