YC-1-inhibited proliferation of rat mesangial cells through suppression of cyclin D1-independent of cGMP pathway and partially reversed by p38 MAPK inhibitor

Drug cytotoxicity screening using human intestinal organoids propagated with extensive cost-reduction strategies

Organoids are regarded as physiologically relevant cell models and useful for compound screening for drug development; however, their applications are currently limited because of the high cost of their culture. We previously succeeded in reducing the cost of human intestinal organoid culture using conditioned medium (CM) of L cells co-expressing Wnt3a, R-spondin1, and Noggin. Here, we further reduced the cost by replacing recombinant hepatocyte growth factor with CM. Moreover, we showed that embedding organoids in collagen gel, a more inexpensive matrix than Matrigel, maintains organoid proliferation and marker gene expression similarly when using Matrigel. The combination of these replacements also enabled the organoid-oriented monolayer cell culture. Furthermore, screening thousands of compounds using organoids expanded with the refined method identified several compounds with more selective cytotoxicity against organoid-derived cells than Caco-2 cells. The mechanism of action of one of these compounds, YC-1, was further elucidated. We showed that YC-1 induces apoptosis through the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway, the mechanism of which was distinct from cell death caused by other hit compounds. Our cost-cutting methodology enables large-scale intestinal organoid culture and subsequent compound screening, which could expand the application of intestinal organoids in various research fields.

YC-1 induces G0/G1 phase arrest and mitochondria-dependent apoptosis in cisplatin-resistant human oral cancer CAR cells

Oral cancer is a serious and fatal disease. Cisplatin is the first line of chemotherapeutic agent for oral cancer therapy. However, the development of drug resistance and severe side effects cause tremendous problems clinically. In this study, we investigated the pharmacologic mechanisms of YC-1 on cisplatin-resistant human oral cancer cell line, CAR. Our results indicated that YC-1 induced a concentration-dependent and time-dependent decrease in viability of CAR cells analyzed by MTT assay. Real-time image analysis of CAR cells by IncuCyte™ Kinetic Live Cell Imaging System demonstrated that YC-1 inhibited cell proliferation and reduced cell confluence in a time-dependent manner. Results from flow cytometric analysis revealed that YC-1 promoted G₀/G₁ phase arrest and provoked apoptosis in CAR cells. The effects of cell cycle arrest by YC-1 were further supported by up-regulation of p21 and down-regulation of cyclin A, D, E and CDK2 protein levels. TUNEL staining showed that YC-1 caused DNA fragmentation, a late stage feature of apoptosis. In addition, YC-1 increased the activities of caspase-9 and caspase-3, disrupted the mitochondrial membrane potential (AYm) and stimulated ROS production in CAR cells. The protein levels of cytochrome c, Bax and Bak were elevated while Bcl-2 protein expression was attenuated in YC-1-treated CAR cells. In summary, YC-1 suppressed the viability of cisplatin-resistant CAR cells through inhibiting cell proliferation, arresting cell cycle at G₀/G₁ phase and triggering mitochondria-mediated apoptosis. Our results provide evidences to support the potentially therapeutic application of YC-1 on fighting against drug resistant oral cancer in the future.

The soluble guanylyl cyclase activator YC-1 increases intracellular cGMP and cAMP via independent mechanisms in INS-1E cells

In addition to increasing cGMP, the soluble guanylyl cyclase (sGC) activator 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) can elevate intracellular cAMP levels. This response was assumed to be as a result of cGMP-dependent inhibition of cAMP phosphodiesterases; however, in this study, we show that YC-1-induced cAMP production in the rat pancreatic beta cell line INS-1E occurs independent of its function as a sGC activator and independent of its ability to inhibit phosphodiesterases. This YC-1-induced cAMP increase is dependent upon soluble adenylyl cyclase and not on transmembrane adenylyl cyclase activity. We previously showed that soluble adenylyl cyclase-generated cAMP can lead to extracellular signal-regulated kinase activation and that YC-1-stimulated cAMP production also stimulates extracellular signal-regulated kinase. Although YC-1 has been used as a tool for investigating sGC and cGMP-mediated pathways, this study reveals cGMP-independent pharmacological actions of this compound.

Reverse phase protein array identifies novel anti-invasion mechanisms of YC-1

YC-1 has recently been demonstrated to have potent anti-invasion and anti-metastatic activity in several cancer models, in addition to its anti-proliferation activity. However, the mechanism underlying its anti-invasion/anti-metastatic activity is largely unknown. Nasopharyngeal carcinoma (NPC) is a highly metastatic head and neck cancer in Southeast Asia. Here, we demonstrated that YC-1 inhibited invasiveness and proliferation of NPC cells, with the latter being accompanied by PARP cleavage, S-phase arrest and activation of Chk1/Chk2. We aimed at identifying novel anti-invasion mechanisms of YC-1 in NPC by a functional proteomic platform, the reverse phase protein array (RPPA). Our study revealed for the first time that multiple invasion-related signaling proteins (beta-catenin, caveolin, Src and EGFR), as well as several growth-related proteins (AMPKalpha, phospho-acetyl-CoA carboxylase (p-ACC), HER-2 and mTOR), which were previously un-described signaling proteins altered by YC-1, were found to be down-modulated by YC-1 in NPC cells. We hypothesized that YC-1-mediated downregulation of these invasion proteins contributed to its anti-invasion activity in NPC cells. Overexpression of EGFR, activated Src or caveolin, but not beta-catenin reversed the inhibitory effects of YC-1 on NPC cell invasion, with EGFR and activated Src having additional effects on rescuing NPC cells from YC-1-mediated growth inhibition. In summary, we have identified several novel anti-invasion mechanisms of YC-1 that could impact NPC, and possibly other cancers as well.

The cyclic GMP modulators YC-1 and zaprinast reduce vessel remodeling through antiproliferative and proapoptotic effects

Guanosine-specific cyclic nucleotide signaling is suggested to serve protective actions in the vasculature; however, the influence of selective pharmacologic modulation of cyclic guanosine monophosphate- synthesizing soluble guanylate cyclase or cyclic guanosine monophosphate-degrading phosphodiesterase on vessel remodeling has not been thoroughly examined. In this study, rat carotid artery balloon injury was performed and the growth-modulating effects of the soluble guanylate cyclase stimulator YC-1 or the cyclic guanosine monophosphate-dependent phosphodiesterase-V inhibitor zaprinast were examined. YC-1 or zaprinast elevated vessel cyclic guanosine monophosphate content, reduced medial wall and neointimal cell proliferation, stimulated medial and neointimal cellular apoptosis, and markedly attenuated neointimal remodeling in comparable fashion. Interestingly, soluble guanylate cyclase inhibition by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one failed to noticeably alter neointimal growth, and concomitant zaprinast with YC-1 did not modify any parameter compared to individual treatments. These results provide novel in vivo evidence that YC-1 and zaprinast inhibit injury-induced vascular remodeling through antimitogenic and proapoptotic actions and may offer promising therapeutic approaches against vasoproliferative disorders.

NO-independent, haem-dependent soluble guanylate cyclase stimulators

The nitric oxide (NO) signalling pathway is altered in cardiovascular diseases, including systemic and pulmonary hypertension, stroke, and atherosclerosis. The vasodilatory properties of NO have been exploited for over a century in cardiovascular disease, but NO donor drugs and inhaled NO are associated with significant shortcomings, including resistance to NO in some disease states, the development of tolerance during long-term treatment, and non-specific effects such as post-translational modification of proteins. The development of pharmacological agents capable of directly stimulating the NO receptor, soluble guanylate cyclase (sGC), is therefore highly desirable. The benzylindazole compound YC-1 was the first sGC stimulator to be identified; this compound formed a lead structure for the development of optimized sGC stimulators with improved potency and specificity for sGC, including CFM-1571, BAY 41-2272, BAY 41-8543, and BAY 63-2521. In contrast to the NO- and haem-independent sGC activators such as BAY 58-2667, these compounds stimulate sGC activity independent of NO and also act in synergy with NO to produce anti-aggregatory, anti-proliferative, and vasodilatory effects. Recently, aryl-acrylamide compounds were identified independent of YC-1 as sGC stimulators; although structurally dissimilar to YC-1, they have a similar mode of action and promote smooth muscle relaxation. Pharmacological stimulators of sGC may be beneficial in the treatment of a range of diseases, including systemic and pulmonary hypertension, heart failure, atherosclerosis, erectile dysfunction, and renal fibrosis. An sGC stimulator, BAY 63-2521, is currently in clinical development as an oral therapy for patients with pulmonary hypertension. It has demonstrated efficacy in a proof-of-concept study, reducing pulmonary vascular resistance and increasing cardiac output from baseline. A full, phase 2 trial of BAY 63-2521 in pulmonary hypertension is underway.

Bradykinin enhances reactive oxygen species generation, mitochondrial injury, and cell death induced by ATP depletion--a role of the phospholipase C-Ca(2+) pathway

This study aimed to study the effect of bradykinin on reactive oxygen species (ROS) generation, mitochondrial injury, and cell death induced by ATP depletion in cell culture. Renal tubular cells were subjected to ATP depletion. Cell death was evaluated with LDH release, sub-G0/G1 fraction, Hoechst staining, and annexin V binding assay. ROS generation, mitochondrial membrane potential (DeltaPsi(m)), and intramitochondrial calcium were evaluated with flow cytometry. Translocation of cytochrome c and activation of apoptotic protein were analyzed with cell fractionating and Western blotting. Intracellular calcium was measured with a spectrofluorometer. Bradykinin enhanced cellular LDH release, apoptosis, generation of superoxide, and hydrogen peroxide induced by ATP depletion. Bradykinin also enhanced the loss of DeltaPsi(m), translocation of cytochrome c into cytosol, and activation of apoptotic protein. The intracellular/mitochondrial calcium was higher in bradykinin-treated cells. All these effects were reversed by coadministration with bradykinin B2 receptor (B2R) antagonist. Besides, blocking the phospholipase C (PLC) could reverse the synergistic effect of bradykinin with ATP depletion on ROS generation, mitochondrial damage, accumulation of intracellular/mitochondrial calcium, and apoptosis. Activation of B2R aggravates ROS generation, mitochondrial damage, and cell death induced by ATP depletion. These effects may act through the PLC-Ca(2+) signaling pathway.

Pathophysiological roles of ASK1-MAP kinase signaling pathways

Apoptosis signal-regulating kinase 1 (ASK1) is a mitogenactivated protein kinase (MAPK) kinase kinase that activates JNK and p38 kinases. ASK1 is activated by various stresses, such as reactive oxygen species (ROS), endoplasmic reticulum (ER) stress, lipopolysaccharide (LPS) and calcium influx which are thought to be responsible for the pathogenesis or exacerbations of various human diseases. Recent studies revealed the involvement of ASK1 in ROS- or ER stressrelated diseases, suggesting that ASK1 may be a potential therapeutic target of various human diseases. In this review, we focus on the current findings for the relationship between pathogenesis and ASK1-MAPK pathways.

Early activation of bradykinin B2 receptor aggravates reactive oxygen species generation and renal damage in ischemia/reperfusion injury

The kallikrein/kinin system is beneficial in ischemia/reperfusion injury in heart, controversial in brain, but detrimental in lung, liver, and intestine. We examined the role of the kallikrein/kinin system in acute ischemia/reperfusion renal injury induced by 40 min occlusion of the renal artery followed by reperfusion. Rats were infused with tissue kallikrein protein 5 days before (pretreated group) or after (treated group) ischemia. Two days later, the pretreated group exhibited the worst renal dysfunction, followed by the treated group, then the control group. Kallikrein increased tubular necrosis and inflammatory cell infiltration with generation of more tumor necrosis factor-alpha and monocyte chemoattractant protein-1. Reactive oxygen species (ROS), malondialdehyde, and reduced/oxidized glutathione measurement revealed that the oxidative stress was augmented by kallikrein administration in both ischemic and reperfusion phases. The groups with more ROS generation also had more apoptotic renal cells. The deleterious effects of kallikrein on ischemia/reperfusion injury were reversed by cotreatment with bradykinin B2 receptor (B2R) antagonist, but not B1 receptor antagonist, and were not associated with hemodynamic changes. We conclude that early activation of B2R augmented ROS generation in ischemia/reperfusion renal injury, resulting in subsequent apoptosis, inflammation, and tissue damage. This finding suggests the potential application of B2R antagonists in acute ischemic renal disease associated with bradykinin activation.

Suppression of hypoxia inducible factor-1alpha (HIF-1alpha) by YC-1 is dependent on murine double minute 2 (Mdm2)

Inhibition of HIF-1alpha activity provides an important strategy for the treatment of cancer. Recently, 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1) has been identified as an anti-HIF-1alpha drug in cancer therapy with unclear molecular mechanism. In the present study, we aimed to investigate the effect and mechanism of YC-1 on HIF-1alpha in a hepatocellular carcinoma cell line under hypoxic condition, which was generated by incubating cells with 0.1% O(2). The phenotypic and molecular changes of cells were determined by cell proliferation assay, apoptosis assay, luciferase promoter assay, and Western blot analysis. YC-1 arrested tumor cell growth in a dose-dependent manner, whereas it did not induce cell apoptosis. Hypoxia-induced upregulation of HIF-1alpha was suppressed by YC-1 administration. YC-1 inhibited HIF-1alpha protein synthesis under normoxia and affected protein stability under hypoxia. YC-1 suppressed the expression of total and phosphorylated forms of murine double minute 2 (Mdm2), whereas this inhibitory effect was blocked by overexpression of Mdm2. In conclusion, YC-1 suppressed both protein synthesis and stability of HIF-1alpha in HCC cells, and its inhibitory effects on HIF-1alpha were dependent on Mdm2.