1. cAMP analogs and their metabolites enhance TREK-1 mRNA and K+ current expression in adrenocortical cells
Judith A Enyeart, Haiyan Liu, John J Enyeart Mol Pharmacol. 2010 Mar;77(3):469-82. doi: 10.1124/mol.109.061861. Epub 2009 Dec 22.
bTREK-1 K(+) channels set the resting membrane potential of bovine adrenal zona fasciculata (AZF) cells and function pivotally in the physiology of cortisol secretion. Adrenocorticotropic hormone controls the function and expression of bTREK-1 channels through signaling mechanisms that may involve cAMP and downstream effectors including protein kinase A (PKA) and exchange protein 2 directly activated by cAMP (Epac2). Using patch-clamp and Northern blot analysis, we explored the regulation of bTREK-1 mRNA and K(+) current expression by cAMP analogs and several of their putative metabolites in bovine AZF cells. At concentrations sufficient to activate both PKA and Epac2, 8-bromoadenosine-cAMP enhanced the expression of both bTREK-1 mRNA and K(+) current. N(6)-Benzoyladenosine-cAMP, which activates PKA but not Epac, also enhanced the expression of bTREK-1 mRNA and K(+) current measured at times from 24 to 96 h. An Epac-selective cAMP analog, 8-(4-chlorophenylthio)-2'-O-methyl-cAMP (8CPT-2'-OMe-cAMP), potently stimulated bTREK-1 mRNA and K(+) current expression, whereas the nonhydrolyzable Epac activator 8-(4-chlorophenylthio)-2'-O-methyl-cAMP, Sp-isomer was ineffective. Metabolites of 8CPT-2'-OMe-cAMP, including 8-(4-chlorophenylthio)-2'-O-methyladenosine-5'-O-monophosphate and 8CPT-2'-OMe-adenosine, promoted the expression of bTREK-1 transcripts and ion current with a temporal pattern, potency, and effectiveness resembling that of the parent compound. Likewise, at low concentrations, 8-(4-chlorophenylthio)-cAMP (8CPT-cAMP; 30 microM) but not its nonhydrolyzable analog 8-(4-chlorophenylthio)-cAMP, Sp-isomer, enhanced the expression of bTREK-1 mRNA and current. 8CPT-cAMP metabolites, including 8CPT-adenosine and 8CPT-adenine, also increased bTREK-1 expression. These results indicate that cAMP increases the expression of bTREK-1 mRNA and K(+) current through a cAMP-dependent but Epac2-independent mechanism. They further demonstrate that one or more metabolites of 8-(4-chlorophenylthio)-cAMP analogs potently stimulate bTREK-1 expression by activation of a novel cAMP-independent mechanism. These findings raise significant questions regarding the specificity of 8-(4-chlorophenylthio)-cAMP analogs as cAMP mimetics.
2. Analgesic dipeptide derivatives. 3. Synthesis and structure-activity relationships of o-nitrophenyl-modified analogues of the analgesic compound H-Lys-Trp(NPS)-OMe
M T Garcia-López, R González-Muñiz, M T Molinero, J R Naranjo, J Del Rio J Med Chem. 1987 Sep;30(9):1658-63. doi: 10.1021/jm00392a023.
A series of analogues of the analgesic dipeptide derivative H-Lys-Trp(NPS)-OMe has been designed to determine the influence of the (2-nitrophenyl)sulfenyl (NPS) moiety on the activity. The syntheses and antinociceptive effects of these analogues of general formula H-Lys-Trp(R)-OMe [R = phenylsulfenyl (PS) (9); R = (2-carbomethyoxyphenyl)sulfenyl (CmPS) (10); R = (4-nitrophenyl)sulfenyl (pNPS) (11); R = (2,4-dinitrophenyl)sulfenyl (DNPS) (12); R = [2-(acetylamino)-2-carbomethoxyethyl]sulfenyl (AacCmES) (13); R = [2-(acetylamino)phenyl]sulfenyl (AacPS) (17); R = tert-butylsulfenyl (t-BuS) (23); R = (2-carbomethoxyethyl)sulfenyl (CmES) (24)] are described. Reaction of Z-Lys(Z)-Trp-OMe (3) with PS-, CmPS-, pNPS-, DNPS-, and AacCmES-Cl afforded the corresponding 2-(sulfenyl)tryptophan derivatives, which on treatment with boron-tris(trifluoroacetate)/trifluoroacetic acid or trimethylsilyl iodide in acetonitrile (Me3SiI/CH3CN) provided 9-13, respectively. Sulfenylation of 3 with NPS-Cl gave Z-Lys(Z)-Trp(NPS)-OMe, which, on catalytic hydrogenation of the nitro group using 10% Pd/C followed by acetylation of the resulting amino function and removal of the protecting Z groups, gave 17. Condensation of 2-(tert-butylsulfenyl)- and 2-[(2-carbomethoxyethyl)sulfenyl]tryptophan methyl ester, obtained by reaction of methyl 3a-hydroxy-1,2,3,3a,8,8a-hexahydropyrrolo[2,3-b]indole-2-carboxyla te with the corresponding thiol, with Z-Lys(Z)-OSu afforded Z-Lys(Z)-Trp(t-BuS)-OMe and Z-Lys(Z)-Trp(CmES)-OMe, which on treatment with Me3SiI/CH3CN provided 23 and 24, respectively. Intracerebroventricular administration of 10 elicited a naloxone-reversible antinociceptive effect in mice similar to that of H-Lys-Trp(NPS)-OMe. No analgesia was however found with the phenylsulfenyl or acyclic sulfenyl substituted dipeptides 9, 11, and 17 or 13, 23, and 24. The Trp(DNPS)-containing analogue was neurotoxic. Structure-activity studies indicate that the role of the NPS and CmPS moieties could be related to the adoption of a preferential active conformation.
3. Ketamine, a Clinically Used Anesthetic, Inhibits Vascular Smooth Muscle Cell Proliferation via PP2A-Activated PI3K/Akt/ERK Inhibition
Yi Chang, Jiun-Yi Li, Thanasekaran Jayakumar, Shou-Huang Hung, Wei-Cheng Lee, Manjunath Manubolu, Joen-Rong Sheu, Ming-Jen Hsu Int J Mol Sci. 2017 Nov 27;18(12):2545. doi: 10.3390/ijms18122545.
Abnormal proliferation of vascular smooth muscle cells (VSMCs) gives rise to major pathological processes involved in the development of cardiovascular diseases. The use of anti-proliferative agents for VSMCs offers potential for the treatment of vascular disorders. Intravenous anesthetics are firmly established to have direct effects on VSMCs, resulting in modulation of blood pressure. Ketamine has been used for many years in the intensive care unit (ICU) for sedation, and has recently been considered for adjunctive therapy. In the present study, we investigated the effects of ketamine on platelet-derived growth factor BB (PDGF-BB)-induced VSMC proliferation and the associated mechanism. Ketamine concentration-dependently inhibited PDGF-BB-induced VSMC proliferation without cytotoxicity, and phosphatidylinositol 3-kinase (PI3K) and extracellular signal-regulated protein kinase (ERK) inhibitors, LY294002 and PD98059, respectively, have similar inhibitory effects. Ketamine was shown to attenuate PI3K, Akt, and ERK1/2 phosphorylation induced by PDGF-BB. Okadaic acid, a selective protein phosphatase 2A (PP2A) inhibitor, significantly reversed ketamine-mediated PDGF-BB-induced PI3K, Akt, and ERK1/2 phosphorylation; a transfected protein phosphatse 2a (pp2a) siRNA reversed Akt and ERK1/2 phosphorylation; and 3-O-Methyl-sphingomyeline (3-OME), an inhibitor of sphingomyelinase, also significantly reversed ERK1/2 phosphorylation. Moreover, ketamine alone significantly inhibited tyrosine phosphorylation and demethylation of PP2A in a concentration-dependent manner. In addition, the pp2a siRNA potently reversed the ketamine-activated catalytic subunit (PP2A-C) of PP2A. These results provide evidence of an anti-proliferating effect of ketamine in VSMCs, showing activation of PP2A blocks PI3K, Akt, and ERK phosphorylation that subsequently inhibits the proliferation of VSMCs. Thus, ketamine may be considered a potential effective therapeutic agent for reducing atherosclerotic process by blocking the proliferation of VSMCs.
