• Archives of Pharmacal Research
• /
• 제27권7호
• /
• pp.683-692
• /
• 2004

Curcumin (diferuloylmethane) is a major naturally-occurring polyphenol of Curcuma species, which is commonly used as a yellow coloring and flavoring agent in foods. Curcumin has shown anti-carcinogenic activity in animal models. Curcumin possesses anti-inflammatory activity and is a potent inhibitor of reactive oxygen-generating enzymes such as lipoxygenase/cyclooxygenase, xanthine dehydrogenase/oxidase and inducible nitric oxide synthase; and an effective inducer of heme oxygenase-1. Curcumin is also a potent inhibitor of protein kinase C(PKC), EGF(Epidermal growth factor)-receptor tyrosine kinase and LĸB kinase. Subsequently, curcumin inhibits the activation of NF(nucleor factor)KB and the expressions of oncogenes including c-jun, c-fos, c-myc, NIK, MAPKs, ERK, ELK, PI3K, Akt, CDKs and iNOS. It is proposed that curcumin may suppress tumor promotion through blocking signal transduction path-ways in the target cells. The oxidant tumor promoter TPA activates PKC by reacting with zinc thiolates present within the regulatory domain, while the oxidized form of cancer chemopreventive agent such as curcumin can inactivate PKC by oxidizing the vicinal thiols present within the catalytic domain. Recent studies indicated that proteasome-mediated degradation of cell proteins playa pivotal role in the regulation of several basic cellular processes including differentiation, proliferation, cell cycling, and apoptosis. It has been demonstrated that curcumin-induced apoptosis is mediated through the impairment of ubiquitin-proteasome pathway. Curcumin was first biotransformed to dihydrocurcumin and tetrahydrocurcumin and that these compounds subsequently were converted to monoglucuronide conjugates. These results suggest that curcumin-glucuronide, dihydrocurcumin-glucuronide, tetrahydrocurcumin-glucuronide and tetrahydrocurcumin are the major metabolites of curcumin in mice, rats and humans.

• 대한수의학회지
• /
• 제38권3호
• /
• pp.508-517
• /
• 1998

There is evidence that the sympathetic nervous system exerts a control on thyroid function via an adrenergic innervation of thyroid cells. Although it is clear that the inhibitory effects of catecholamines result from an activation of ${\alpha}_1$-adrenoceptors, the mechanisms involved in ${\alpha}_1$-stimulation are not fully understood. The effects of methoxamine and protein kinase C (PKC) activator on the release of thyroxine ($T_4$) from mouse thyroid were studied to clarify the role of PKC in the regulation of $T_4$ release in vitro. The glands were incubated in the medium, samples of the medium were assayed for $T_4$ by EIA kits. Methoxamine inhibited the TSH-stimulated $T_4$ release. This inhibition was reversed by prazosin, an ${\alpha}_1$-adrenergic antagonist. Futhermore, the inhibitory effect of methoxamine on the $T_4$ release stimulated by TSH was prevented by chloroethylclonidine, an ${\alpha}_{1b}$-adrenoceptor antagonist, but not by WB4101, an ${\alpha}_{1a}$-adrenoceptor antagonist. Also methoxamine inhibited the forskolin-, cAMP- or IBMX-stimulated $T_4$ release. These inhibition were reversed by PKC inhibitors, such as staurosporine and $H_7$. PMA, a PKC activator, completely inhibited the TSH-stimulated $T_4$ release, and its inhibition was reversed by staurosporine and $H_7$, but not by chelerythrine. R59022 (a diacylglycerol kinase inhibitor), like methoxamine, also inhibited the TSH-stimulated $T_4$ release, and its inhibition was also reversed by staurosporine. The present study suggests that methoxamine inhibition of $T_4$ release from mouse thyroid can be induced by activation of the ${\alpha}_{1b}$-adrenoceptors and that it is mediated through the ${\alpha}_1$-adrenoceptor-stimulated PKC formation.

• Molecules and Cells
• /
• 제25권4호
• /
• pp.504-509
• /
• 2008

Three G-protein-linked acetylcholine receptors (GARs) exist in the nematode C. elegans. GAR-3 is pharmacologically most similar to mammalian muscarinic acetylcholine receptors (mAChRs). We observed that carbachol stimulated ERK1/2 activation in Chinese hamster ovary (CHO) cells stably expressing GAR-3b, the predominant alternatively spliced isoform of GAR-3. This effect was substantially reduced by the phospholipase C (PLC) inhibitor U73122 and the protein kinase C (PKC) inhibitor GF109203X, implying that PLC and PKC are involved in this process. On the other hand, GAR-3b-mediated ERK1/2 activation was inhibited by treatment with forskolin, an adenylate cyclase (AC) activator. This inhibitory effect was blocked by H89, an inhibitor of cAMP-dependent protein kinase A (PKA). These results suggest that GAR-3b-mediated ERK1/2 activation is negatively regulated by cAMP through PKA. Together our data show that GAR-3b mediates ERK1/2 activation in CHO cells and that GAR-3b can couple to both stimulatory and inhibitory pathways to modulate ERK1/2.

• Archives of Pharmacal Research
• /
• 제27권3호
• /
• pp.324-333
• /
• 2004

To determine whether Insulin-like growth factor (IGF-I) treatment represents a potential means of enhancing the survival of cardiac muscle cells from adriamycin (ADR)-induced cell death, the present study examined the ability of IGF-I to prevent cell death. The study was performed utilising the embryonic, rat, cardiac muscle cell line, H9C2. Incubating cardiac muscle cells in the presence of adriamycin increased cell death, as determined by MTT assay and annexin V-positive cell number. The addition of 100 ng/mL IGF-I, in the presence of adriamycin, decreased apoptosis. The effect of IGF-I on phosphorylation of PI, a substrate of phosphatidylinositol 3-kinase (PI 3-kinase) or protein kinase B (AKT), was also examined in H9C2 cardiac muscle cells. IGF-I increased the phosphorylation of ERK 1 and 2 and $PKC{\;}{\zeta}{\;}kinase$. The use of inhibitors of PI 3-kinase (LY 294002), in the cell death assay, demonstrated partial abrogation of the protective effect of IGF-I. The MEK1 inhibitor-PD098059 and the PKC inhibitor-chelerythrine exhibited no effect on IGF-1-induced cell protection. In the regulatory subunit of PI3K-p85- dominant, negative plasmid-transfected cells, the IGF-1-induced protective effect was reversed. This data demonstrates that IGF-I protects cardiac muscle cells from ADR-induced cell death. Although IGF-I activates several signaling pathways that contribute to its protective effect in other cell types, only activation of PI 3-kinase contributes to this effect in H9C2 cardiac muscle cells.

• Molecules and Cells
• /
• 제37권10호
• /
• pp.747-752
• /
• 2014

Protein kinase C (PKC) family members phosphorylate a wide variety of protein targets and are known to be involved in diverse cellular signaling pathways. However, the role of PKC in receptor activator of NF-${\kappa}B$ ligand (RANKL) signaling has remained elusive. We now demonstrate that $PKC{\beta}$ acts as a positive regulator which inactivates glycogen synthase kinase-$3{\beta}$ (GSK-$3{\beta}$) and promotes NFATc1 induction during RANKL-induced osteoclastogenesis. Among PKCs, $PKC{\beta}$ expression is increased by RANKL. Pharmacological inhibition of $PKC{\beta}$ decreased the formation of osteoclasts which was caused by the inhibition of NFATc1 induction. Importantly, the phosphorylation of GSK-$3{\beta}$ was decreased by $PKC{\beta}$ inhibition. Likewise, down-regulation of $PKC{\beta}$ by RNA interference suppressed osteoclast differentiation, NFATc1 induction, and GSK-$3{\beta}$ phosphorylation. The administration of PKC inhibitor to the RANKL-injected mouse calvaria efficiently protected RANKL-induced bone destruction. Thus, the $PKC{\beta}$ pathway, leading to GSK-$3{\beta}$ inactivation and NFATc1 induction, has a key role in the differentiation of osteoclasts. Our results also provide a further rationale for $PKC{\beta}$'s therapeutic targeting to treat inflammation-related bone diseases.

• 대한의생명과학회지
• /
• 제12권3호
• /
• pp.217-224
• /
• 2006

It has been reported that the dysfunctions of podocytes are associated with the development of diabetic nephropathy. In addition, insulin-like growth factors (IGFs) are associated with the development of diabetic nephropathy. However, it is not yet known about the effect of high glucose on IGF-I, -II secretion, and IGF binding proteins (IGFBPs) expression in the podocytes. Thus, this study was conducted to examine the effect of high glucose on IGF system and its involvement of protein kinase C (PKC) and mitogen activated protein kinases (MAPKs) in podocytes. In this study, high glucose (25 mM) increased IGF-I and IGF-II secretion (P<0.05), which was blocked by SB 203580 (a p38 MAPK inhibitor) but not by PD 98059 (a p44/42 MAPK inhibitor). In addition, high glucose-induced stimulation of IGFs was blocked by bisindolylmaleimide I and staurosporine (protein kinase C inhibitors). High glucose also increased IGFBP-l expression, which was blocked by bisindolylmaleimide I and SB 203580. In conclusion, high glucose alters IGFs secretion and IGFBP expression via PKC and p38 MAPK pathways in podocytes.

• Molecules and Cells
• /
• 제21권2호
• /
• pp.237-243
• /
• 2006

Brain-derived neurotrophic factor (BDNF) is a neuromodulator of nociceptive responses in the dorsal root ganglia (DRG) and spinal cord. BDNF synthesis increases in response to nerve growth factor (NGF) in trkA-expressing small and medium-sized DRG neurons after inflammation. Previously we demonstrated differential activation of multiple BDNF promoters in the DRG following peripheral nerve injury and inflammation. Using reporter constructs containing individual promoter regions, we investigated the effect of NGF on the multiple BDNF promoters, and the signaling pathway by which NGF activates these promoters in PC12 cells. Although all the promoters were activated 2.4-7.1-fold by NGF treatment, promoter IV gave the greatest induction. The p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580, phosphatidylinositol 3-kinase (PI-3K) inhibitor, LY294003, protein kinase A (PKA) inhibitor, H89, and protein kinase C (PKC) inhibitor, chelerythrine, had no effect on activation of promoter IV by NGF. However, activation was completely abolished by the MAPK kinase (MEK) inhibitors, U0126 and PD98059. In addition, these inhibitors blocked NGF-induced phosphorylation of extracellular signal-regulated protein kinase (ERK) 1/2. Taken together, these results suggest that the ERK1/2 pathway activates BDNF promoter IV in response to NGF independently of NGF-activated signaling pathways involving PKA and PKC.

• Archives of Pharmacal Research
• /
• 제27권7호
• /
• pp.757-762
• /
• 2004

The protective adaptive response to electrophiles and reactive oxygen species is mediated by the induction of phase II detoxifying genes including glutathione S-transferases (GSTs). NF-E2-related factor-2 (Nrf2) phosphorylation by protein kinase C (PKC) is a critical event for its nuclear translocation in response to oxidative stress. Previously, we have shown that peroxynitrite plays a role in activation of Nrf2 and Nrf2 binding to the antioxidant response element (ARE) via the pathway of phosphatidylinositol 3-kinase (PI3-kinase) and that nitric oxide synthase in hepatocytes is required for GSTA2 induction. In view of the importance of PKC and Pl3-kinase in Nrf2-mediated GST induction, we investigated the role of these kinases in peroxynitrite formation for GSTA2 induction by oxidative stress and determined the relationship between PKC and PI3-kinase. Although PKC activation by phorbol 12-myristate-13-acetate (PMA) did not increase the extents of constitutive and inducible GSTA2 expression, either PKC depletion by PMA or PKC inhibition by staurosporine significantly inhibited GSTA2 induction by tert-butylhydroquinone (t-SHa) a prooxidant chemical. Therefore, the basal PKC activity is req- uisite for GSTA2 induction. 3-Morpholinosydnonimine (SIN-1), which decomposes and yields peroxynitrite, induced GSTA2, which was not inhibited by PKC depletion, but slightly enhanced by PKC activation, suggesting that PKC promotes peroxynitrite formation for Nrf2-mediated GSTA2 induction. Treatment of cells with S-nitroso-N-acetyl-penicillamine (SNAP), an exogenous NO donor, in combination with t-BHQ may produce peroxynitrite. GSTA2 induction by SNAP ＋ t-BHQ was not decreased by PKC depletion, but rather enhanced by PKC activation, showing that the activity of PKC might be required for peroxynitrite formation. LY294002 a P13-kinase inhibitor blocked GSTA2 induction by t-BHQ, which was reversed by PMA-induced PKC activation. These results provide evidence that PKC may playa role in formation of peroxynitrite that activates Nrf2 for GSTA2 induction and that PKC may serve an activator for GSTA2 induction downstream of PI3-kinase.

• The Korean Journal of Physiology and Pharmacology
• /
• 제5권6호
• /
• pp.503-510
• /
• 2001

Long-term treatment of cultured bovine adrenal medullary chromaffin (BAMC) cells with arachidonic acid $(100\;{\mu}M),$ angiotesnin II (100 nM), prostaglandin $E_2\;(PGE_2;\;10\;{\mu}M),$ veratridine $(2\;{\mu}M)$ or KCl (55 mM) for 24 hrs increased both norepinephrine and epinephrine levels in the supernatant. Pretreatment with staurosporine (10 nM), a protein kinase C (PKC) inhibitor, completely blocked increases of norepinephrine and epinephrine secretion induced by arachidonic acid, angiotensin II, $PGE_2,$ veratridine or KCl. In addition, K252a, another PKC inhibitor whose structure is similar to that of staurosporine, effectively attenuated both norepinephrine and epinephrine secretion induced by arachidonic acid. However, K252a did not affect the catecholamine secretion induced by angiotensin II, $PGE_2,$ veratridine or KCl. Our results suggest that staurosporine may inhibit long-term catecholamine secretion induced by various secretagogues in a mechanism other than inhibiting PKC signaling. Furthermore, long-term secretion of catecholamines induced by arachidonic acid may be dependent on PKC pathway.

• 대한소아치과학회지
• /
• 제29권3호
• /
• pp.337-344
• /
• 2002

조골 세포의 분화에 중요한 역할을 하는 전사 인자인 Runx2는 그 역할은 많이 알려져 있지만, 이를 조절하는 신호 전달체계에 대해서는 많이 알려지지 않았다. 이에 본 연구에서는 조골 세포의 분화 및 증식에 영향을 미친다고 알려진 PKC 및 MAPK pathway가 Runx2에 미치는 영향을 알아보고자 하였다. PKC활성화에 따른 Runx2의 전사 활성 및 발현 양상을 관찰하기 위해 6XOSE2-C2C12 cell에 PKC 활성제를 처리하여 luciferase assay와 Northern blot analysis를 시행하였다. MAPK 활성화에 따른 Runx2의 전사 활성을 관찰하기 위해 MAPK 활성제를 6XOSE2-C2C12 cell에 처리하여 luciferase assay를 시행하였다. 두 신호 전달 체계의 활성화에 따른 골 표지 유전자의 전사 양상을 관찰하기 위해 osteocalcin과 osteopontin을 transient transfection한 C2C12 cell에 각 신호 전달 체계의 활성제를 처리하여 luciferase assay를 시행하였다. 또한 각 신호 전달 체계가 상호 작용하는지 알아보기 위하여 MAPK 억제제를 전처리하여 MAPK pathway를 차단한 1 시간 뒤 PKC 활성제를 처리하고 luciferase assay를 시행하여 Runx2의 전사 활성을 관찰하였다. 이상의 실험으로 다음과 같은 결론을 얻었다. - PKC pathway의 활성화는 Runx2의 전사 활성 및 발현을 증가시키고 이로 인해 그의 영향을 받는 골 표지 유전자 (osteopontin, osteocalcin)의 전사도 증가한다. - MAPK pathway의 활성화는 Runx2 및 골 표지 유전자 (osteopontin, osteocalcin)의 전사활성을 증가시킨다. - PKC pathway는 MAPK pathway를 경유하여 Runx2의 전사 활성을 조절한다.