Hepatitis C virus nonstructural protein 4B (NS4B) is an endoplasmic reticulum (ER) membrane associated protein and a potent causative factor of ER stress. Here we reported that unfolded protein response (UPR) can be activated by HCV NS4B through inducing both XBP1 mRNA splicing and ATF6 cleavage in human hepatic cells. Flow cytometric analysis revealed that HCV NS4B stimulates the production of reactive oxygen species (ROS) by perturbing intracellular Ca(2+) homeostasis. Luciferase assay showed that HCV NS4B also activates the multifunctional transcription factor, NF-kappaB, in a dose-dependent manner through Ca(2+) signaling and ROS. Further immunoblot analysis showed that HCV NS4B promotes NF-kappaB translocation into the nucleus via protein-tyrosine kinase (PTK) mediated phosphorylation and subsequent degradation of IkappaBalpha. These studies provide an important insight into the implication of NS4B in HCV life cycle and HCV-associated liver disease by affecting host intracellular signal transduction pathways.

It is becoming apparent that the synthesis of nitric oxide (NO) from L-arginine not only explains endothelium-dependent vascular relaxation, but is a widespread mechanism for the regulation of cell function and communication. We examined the role of NO on the endogenous dopamine (DA) release from rat striatum. Nitroprusside, in the concentration range of 3-100 microM, induced a dose-dependent increase in the endogenous DA release from rat striatal slices. The maximal response was 330% over the baseline release. A higher concentration of nitroprusside (300 microM) produced an inhibitory effect on the spontaneous release of DA. L-Arginine (10 and 100 microM), a substrate in the NO-forming enzyme system, also produced an elevation of DA release. L-Arginine-induced DA release was attenuated by NG-monomethyl-L-arginine, an inhibitor of NO synthase. NADPH (1 microM), a cofactor of NO synthase, enhanced L-arginine-induced DA release. These results suggest a possible involvement of NO in the DA release process in rat striatum.

1 This study examined whether Paeoniflorin (PF), the major active components of Chinese herb Paeoniae alba Radix, has neuroprotective effect in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease (PD). 2 Subcutaneous administration of PF (2.5 and 5 mg kg À1 ) for 11 days could protect tyrosine hydroxylase (TH)-positive substantia nigra neurons and striatal nerve fibers from death and bradykinesia induced by four-dose injection of MPTP (20 mg kg À1 ) on day 8. 3 When given at 1 h after the last dose of MPTP, and then administered once a day for the following 3 days, PF (2.5 and 5 mg kg À1 ) also significantly attenuated the dopaminergic neurodegeneration in a dose-dependent manner. Post-treatment with PF (5 mg kg À1 ) significantly attenuated MPTP-induced proinflammatory gene upregulation and microglial and astrocytic activation. 4 Pretreatment with 0.3 mg kg À1 8-cyclopentyl-1,3-dipropylxanthine, an adenosine A 1 receptor (A 1 AR) antagonist, 15 min before each dose of PF, reversed the neuroprotective and antineuroinflammatory effects of PF. 5 In conclusion, this study demonstrated that PF could reduce the MPTP-induced toxicity by inhibition of neuroinflammation by activation of the A 1 AR, and suggested that PF might be a valuable neuroprotective agent for the treatment of PD.