For resting pain relief, hyaluronate sodium seems to be as effective as NSAIDs. Further, for pain with physical activity and functional performance, hyaluronate sodium may be superior to placebo alone or NSAIDs alone.
A series of N2-substituted guanine derivatives was screened against mammalian thymidine kinase and the thymidine kinase encoded by type I herpes simplex virus to examine their capacity to selectivity inhibit the viral enzyme. Several bases, nucleosides, and nucleotides displayed selective activity. The mechanism of action of the most potent derivative, N2-phenyl-2'-deoxyguanosine (PhdG) was studied in detail. PhdG (a) inhibited the viral enzyme competitively with respect to the substrates thymidine and deoxycytidine, (b) was completely resistant to phosphorylation, (c) displayed limited toxicity for the HeLa cell lines employed as hosts for viral infection, and (d) selectively inhibited viral thymidine kinase function in intact cultured cells. The results indicate that the PhdG drug prototype has potential as a selective anti-herpes agent and as a novel molecular probe of the structure and function of herpes simplex thymidine kinase.
To determine the minimal sequence requirements for steroid binding and dimerization of human sex hormone-binding globulin (SHBG), the SHBG polypeptide and various SHBG deletion mutants were expressed as glutathione S-transferase (GST) fusion proteins in Escherichia coli. Fusion proteins containing the complete SHBG sequence, or the first 177 N-terminal residues of SHBG, bound steroids with high affinity and specificity. Further deletions from the C-terminus severely compromised steroid-binding activity, as did N-terminal deletions beyond residue 18 in the SHBG sequence. Thus, residues 18-177 in SHBG encompass a region required for its steroid-binding activity, and a disulfide bridge normally present between Cys-164 and Cys-188 in SHBG is not obviously essential for steroid binding. Most of the GST/SHBG fusion proteins undergo cleavage at 4 degrees C, releasing immunoreactive polypeptides that correspond approximately in size to their respective SHBG sequences. The 23-kDa immunoreactive cleavage product released from the fusion protein containing residues 1-205 in the SHBG sequence (SHBG 1-205) has a 50-fold greater steroid-binding capacity but a 7.5-fold lower affinity than its parent fusion protein. In addition, the 22-kDa immunoreactive polypeptide released from SHBG(1-194) binds steroid, and its dimerization is promoted by steroid ligands that bind SHBG with high affinity. These data suggest that the N-terminal region of SHBG dimerizes readily in the absence of GST and in doing so acquires steroid-binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)
Two specific inhibitors of herpes simplex virus thymidine kinase, N2-phenyl-2'-deoxyguanosine and N2-(m-trifluoromethylphenyl)guanine, were tested for their ability to inhibit the reactivation of virus from explant cultures of latently infected murine trigeminal ganglia. Both compounds significantly diminished the frequency of reactivation compared with that of untreated controls. We and others have recently shown that although thymidine kinase (TK)-negative HSV mutants fail to reactivate after explant culture, they do express the latency-associated transcripts in sensory neuronal nuclei (2, 11, 18) and can be reactivated by superinfection-rescue with complementing virus (2, 4). These data demonstrate that TK is not required for establishment of latency and suggest that TK is required for reactivation.The apparent requirement for TK in animal models of latency and pathogenesis has led to efforts to develop anti-HSV drugs that inhibit HSV TK specifically (reviewed in reference 15). Two such drugs are N2-phenyl-2'-deoxyguanosine (PhdG) and N2-(m-trifluoromethylphenyl)guanine (m-CF3PhG) (6,7,15). These compounds are N2-substituted guanines, a family of compounds that can inhibit TK by competition with the enzyme substrates thymidine and deoxycytidine (15). Both PhdG and m-CF3PhG have demonstrated potent and selective inhibition of HSV TK in vitro (6, 7), and PhdG has been shown to inhibit HSV TK in HeLa cells and exhibit minimal cytotoxicity (6). m-CF3PhG also appears to be minimally cytotoxic; at 133 ,uM it had no detectable effect on the growth or morphology of HeLa cells, and neither it nor PhdG affected the morphology of Vero cells at concentrations up to 300 ,uM (unpublished results).In this study we used PhdG and m-CF3PhG in an animal model of HSV latency to test whether the selective inhibition of TK observed in vitro could translate to a selective inhibition of reactivation from explant cultures of latently infected murine trigeminal ganglia. These experiments allowed us to assess further the role of TK in the reactivation * Corresponding author.
A series of N2-phenylguanines was synthesized and tested for inhibition of the thymidine kinases encoded by Herpes simplex viruses type 1 and type 2. Compounds with hydrophobic, electron-attracting groups in the meta position of the phenyl ring such as m-trifluoromethyl (m-CF3PG, IC50 = 0.1 microM) were the most potent inhibitors of both enzymes. Many derivatives were significantly more potent against the type 2 thymidine kinase, and can effectively discriminate between the two enzymes. Among other N2-substituted guanines, alkyl and benzyl derivatives were moderately potent inhibitors, and the type 2 enzyme was again more sensitive than the type 1 enzyme. None of the compounds inhibited the thymidine kinase isolated from the host HeLa cell line, suggesting that members of this class of compounds may be useful nonsubstrate, antiviral compounds for latent herpesvirus infections.
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