H-7 dihydrochloride

The protein kinase C inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7) inhibits PMA-induced promiscuous cytolytic activity but not specific cytolytic activity by a cloned cytolytic T lymphocyte.[Pubmed:1898396]

Biochem Biophys Res Commun. 1991 Sep 16;179(2):720-5.

Phorbol 12-myristate 13-acetate (PMA) induces the cytolytic T lymphocyte (CTL) clone 4D (H-2b anti-H-2d) to promiscuously kill the inappropriate target EL-4 (H-2b). The protein kinase C (PKC) inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7) inhibited the PMA-induced promiscuous lympholysis. The concentration of H-7 that inhibited PMA-induced lympholysis by 50% (IC50) was calculated to be 4 microM, which closely approximates the reported IC50 of H-7 of 6 microM for PKC activity in vitro. In striking contrast, specific cytolysis of appropriate P815 (H-2d) target cell by CTL clone 4D was not inhibited by concentrations of H-7 which inhibited PMA-induced promiscuous lympholysis. These results indicate that PMA-induced promiscuous lympholysis of inappropriate target cell is triggered via activation of PKC, whereas PKC activation is not obligatory in triggering CTL clone 4D to specifically kill appropriate target cells. Thus, these data suggest that cloned CTL have two or more triggering mechanisms than may initiate one or more cytolytic pathways.

Preincubation of thymocytes with 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7) induces apoptosis in non-stimulated thymocytes.[Pubmed:9247701]

Biochem Mol Biol Int. 1997 Jul;42(3):433-41.

1-(5-Isoquinolinesulfonyl1)-2-methylpiperazine hydrochloride (H-7), an inhibitor of protein kinases, has been shown to inhibit the thymocyte apoptosis induced by various apoptogenic agents. In the present study, when mouse thymocytes were pretreated with H-7, washed, and cultured for an additional time, apoptosis was induced depending on the preincubation time and the dose of H-7. The protein kinase C activity in the H-7-pretreated and -washed cells was not altered, suggesting that an alteration of a certain PKC isoform is related to both the triggering and the progression of apoptosis.

Effects of protein kinase inhibitors 1(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7) and N-[2-guanidinoethyl]-5-isoquinolinesulfonamide hydrochloride (HA1004) on calcitriol-induced differentiation of HL-60 cells.[Pubmed:3422561]

Biochem Pharmacol. 1988 Feb 15;37(4):635-40.

HL-60 promyelocytic leukemia cells were induced to differentiate by 1,25-dihydroxyvitamin D3 (calcitriol) into mature monocytes. Differentiation was assessed by nitro blue tetrazolium dye reduction, nonspecific esterase activity, and DNA synthesis. Terminal differentiation of cultures induced by calcitriol (10 nM) was inhibited by 80% when cells were treated simultaneously with protein kinase inhibitors 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7) (32 microM) and N-[2-guanidinoethyl]-5-isoquinolinesulfonamide hydrochloride (HA1004) (320 microM). The IC50 for inhibition of calcitriol-induced differentiation was approximately 15 microM for H-7 and 170 microM for HA1004. The IC50 values for H-7 and HA1004 antagonism of calcitriol-induced differentiation are quantitatively and relatively correlated to their known action to inhibit protein kinase C activity. Treatment of cells with concentrations of 0-32 microM H-7 or 0-320 microM HA1004 alone did not affect cell growth, differentiation, or trypan blue exclusion. However, higher concentrations of H7 (greater than 32 microM) and HA1004 (greater than 320 microM) were found to be cytotoxic. The data presented suggest that calcitriol-induced differentiation is antagonized by inhibitors of protein kinase and are consistent with the hypothesis that kinase C activity is required for HL-60 cell differentiation.

Modulation of inhibitory efficiency of rat skeletal muscle calpastatin by phosphorylation.[Pubmed:1530632]

Biochem Biophys Res Commun. 1992 Sep 16;187(2):751-9.

Rat skeletal muscle calpastatin form is markedly modified in its inhibitory properties by means of a reverse reaction which involves both phosphorylation and dephosphorylation. Dephospho-calpastatin shows greater inhibitory efficiency versus mu-calpain, whereas phospho-calpastatin shows maximal inhibition versus m-calpain. Both forms are present in fresh rat muscle. Phosphorylation has been reproduced "in vitro" using a homologous Ca2+ independent protein kinase and found to result in the incorporation of approximately one mole of 32P per mole of protein. Dephosphorylation was induced by treatment with alkaline phosphatase and 32P release shown found to correlate with modifications of the inhibitory properties. This reversible covalent modification of calpastatin is considered an important advancement in the understanding of how different calpain isoforms can be more efficiently controlled by a single inhibitor isozyme form.

Effect of the kinase inhibitor, H-7, on stress, crossbridge phosphorylation, muscle shortening and inositol phosphate production in rabbit arteries.[Pubmed:2299593]

J Pharmacol Exp Ther. 1990 Jan;252(1):253-9.

Smooth muscle contractile agents cause large increases in crossbridge phosphorylation (Mp) and cycling rates resulting in the rapid development of stress (force/muscle cross-sectional area). Despite temporal declines in Mp and cycling during continued activation, stress is maintained at high levels. This observation led to several different hypotheses describing the regulation of steady-state stress. One proposal is that protein kinase C regulates stress maintenance, whereas another invokes a steady-state dependence on Ca+(+)-calmodulin-dependent myosin light chain kinase. The aim of this study was to investigate the mechanism of stress-maintenance by analyzing the inhibitory efficacy of a protein kinase C inhibitor, H-7 [1-(5-isoquinolinesulfonyl)-2-methylpiperizine], on steady-state values of stress, Mp and crossbridge cycling in rabbit renal and femoral arteries. H-7 effectively inhibited steady-state stress produced by KCl (IC50 = 3.7-4.4 microM) and phenylephrine (PhE) (IC50 = 10.6-15.2 microM). Likewise, increases in the level of Mp and the rate of crossbridge cycling induced by both KCl and PhE were significantly reduced by 10 microM H-7. H-7 did not reduce inositol phosphate production stimulated by PhE, but did reduce early stress development thought to be mediated by inositol phosphate-induced mobilization of intracellular calcium. Calcium-induced increases in stress and Mp produced in saponin-skinned artery strips were reduced by less than 50% by 320 microM H-7.(ABSTRACT TRUNCATED AT 250 WORDS)

Isoquinolinesulfonamides, novel and potent inhibitors of cyclic nucleotide dependent protein kinase and protein kinase C.[Pubmed:6238627]

Biochemistry. 1984 Oct 9;23(21):5036-41.

Naphthalenesulfonamides such as N-(6-amino-hexyl)-5-chloro-1-naphthalenesulfonamide (W-7) are potent calmodulin (CaM) antagonists and act upon several protein kinases at higher concentration. When the naphthalene ring was replaced by isoquinoline, the derivatives were no longer CaM antagonists but retained the ability to inhibit protein kinases, and some of the derivatives exhibited selective inhibition toward a certain protein kinase. cAMP-dependent, cGMP-dependent, and Ca2+-phospholipid-dependent (protein kinase C) protein kinases were inhibited significantly by addition of 10(-6) M N-[2-(methylamino)ethyl]-5-isoquinoline-sulfonamide (H-8) and 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7). H-8 was the most active of the inhibitors in this series and inhibited more markedly cyclic nucleotide dependent protein kinases, than other kinases, while the derivative with the sulfonylpiperazine residue (H-7) was the most potent in inhibiting protein kinase C. Apparent Ki values of H-8 were 0.48 and 1.2 microM for cGMP-dependent and cAMP-dependent protein kinases, respectively, and the Ki value of H-7 for protein kinase C was 6 microM. Both the holoenzyme and the catalytic subunit (or fragment), which is active without an enzyme activator, are susceptible to these compounds with a similar concentration dependency, thereby indicating that the inhibitory effect is attributed to the direct interaction of the compound with the active center of the enzyme but not with the enzyme activator. The inhibitions were freely reversible and of the competitive type with respect to ATP and of the noncompetitive type with respect to the phosphate acceptor.(ABSTRACT TRUNCATED AT 250 WORDS)