ABSTRACT
Objectives: To explore the role of mTOR signaling pathway in modulating epileptogenesis in an N-methyl-D-aspartic acid (NMDA)-induced infant spasm (IS) rat model. Methods: After inducing IS successfully, the phosphorylation status of PI3K, Akt, mTOR and S6K of brain and hippocampus tissues was assessed using western blot and immunochemistry analysis, respectively. The possible mechanism of mTOR signaling pathway was evaluated by the, inhibitors for mTOR and PI3K, rapamycin and wortmannin, respectively. The inhibitors were injected into the intraperitoneal space of the rats to examine the effects of PI3K and mTOR in IS rat model. Results: The phosphorylated levels of mTOR and PI3K in hippocampus increased significantly (P < 0.05) 7 days after IS induction in rats. After administration of wortmannin, the phosphorylated levels of PI3K and mTOR decreased. However, only the phosphorylated level of mTOR decreased obviously after rapamycin administration. No obvious neurogenesis was found after IS induction. Discussion: Results of the present study suggest that hippocampal PI3K may be another potential target for IS treatment.
Subject(s)
Hippocampus/enzymology , Phosphatidylinositol 3-Kinase/metabolism , Spasm/enzymology , TOR Serine-Threonine Kinases/metabolism , Animals , Cell Death , Disease Models, Animal , Female , Hippocampus/drug effects , Hippocampus/pathology , N-Methylaspartate/administration & dosage , Phosphorylation , Protein Kinase Inhibitors/administration & dosage , Rats, Sprague-Dawley , Signal Transduction , Sirolimus/administration & dosage , Spasm/chemically induced , Spasm/pathology , Wortmannin/administration & dosageABSTRACT
In a number of isolated blood vessel types, hypoxia causes an acute contraction that is dependent on the presence of nitric oxide and activation of soluble guanylyl cyclase. It is more pronounced when the preparations are constricted and is therefore termed hypoxic augmentation of vasoconstriction. This hypoxic response is accompanied by increases in the intracellular level of inosine 5'-triphosphate and in the synthesis of inosine 3',5'-cyclic monophosphate (cIMP) by soluble guanylyl cyclase. The administration of exogenous cIMP or inosine 5'-triphosphate causes augmented vasoconstriction to hypoxia. Furthermore, the vasoconstriction evoked by hypoxia and cIMP is associated with increased activity of Rho kinase (ROCK), indicating that cIMP may mediate the hypoxic effect by sensitizing the myofilaments to Ca through ROCK. Hypoxia is implicated in exaggerated vasoconstriction in the pathogenesis of coronary artery disease, myocardial infarction, hypertension, and stroke. The newly found role of cIMP may help to identify unique therapeutic targets for certain cardiovascular disorders.
Subject(s)
Arterial Occlusive Diseases/etiology , Endothelium, Vascular/enzymology , Guanylate Cyclase/metabolism , Hypoxia/complications , Muscle, Smooth, Vascular/enzymology , Receptors, Cytoplasmic and Nuclear/metabolism , Spasm/etiology , Vasoconstriction , Animals , Arterial Occlusive Diseases/enzymology , Arterial Occlusive Diseases/physiopathology , Calcium Signaling , Cyclic IMP/metabolism , Endothelium, Vascular/physiopathology , Humans , Hypoxia/enzymology , Hypoxia/physiopathology , Muscle, Smooth, Vascular/physiopathology , Second Messenger Systems , Soluble Guanylyl Cyclase , Spasm/enzymology , Spasm/physiopathology , rho-Associated Kinases/metabolismABSTRACT
The control of smooth muscle contraction is an important factor in maintaining normal intraocular pressure. However, the specific factors causing changes in control by phosphorylation/dephosphorylation schemes in the eye are not well-defined. The purposes of this experiment were to (i) determine the localization of ROCK (Rho-associated, coiled coil-forming kinase) in monkey and rabbit eye tissues and (ii) measure phosphorylation of ROCK substrate during trabecular meshwork or ciliary muscle contraction induced by carbachol. We found that mRNAs for both ROCK I and II were expressed in most eye tissues from rabbit and monkey. Proteins for ROCK I and II were present in all eye tissues studied except lens. When trabecular meshwork or ciliary muscle were incubated with carbachol to induce contraction, phosphorylation of the myosin-binding subunit (MBS) of myosin phosphatase, a substrate for ROCK, started within 1 min and continued for at least 1 h. This phosphorylation was well correlated with contraction of trabecular meshwork or ciliary muscle. These results suggested that ROCK might regulate contraction of trabecular meshwork or ciliary muscle through phosphorylation of MBS of myosin phosphatase.
