Melatonin Attenuates Vascular Smooth Muscle Contraction Through the γ-Secretase/Notch Intracellular Domain/Myocardin Pathway.

ABSTRACT: Inositol 1, 4, 5-trisphosphate (IP3) signaling-mediated calcium release drives the contraction of vascular smooth muscles and hence regulates blood vessel volume and blood pressure. Melatonin supplementation has been suggested to be beneficial for hypertension. To determine whether the blood pressure-lowering effect of melatonin was accounted for by IP3 signaling, we evaluated the vasoconstriction response and IP3 signaling in isolated mouse thoracic aortic rings during melatonin incubation. C57BL/6 mice were given intraperitoneal injections daily with melatonin, and the systolic blood pressure and contractility of aortic rings from melatonin-treated mice were decreased, and the contraction suppression effect of melatonin was attributed to the impaired expression of contractile proteins in vascular smooth muscle cells rather than IP3 signaling. Our results further showed that melatonin increased the expression of γ-secretase, which could cleave and release the notch intracellular domain, and the notch intracellular domain prevented the transcription of contractile genes by interfering with the interaction between serum response factor and myocardin, the master regulator of contractile protein. In this article, we report a novel mechanism by which melatonin regulates smooth muscle contractility that does not depend on IP3 signaling.

Human ATP-Binding Cassette Transporter ABCB1 Confers Resistance to Volasertib (BI 6727), a Selective Inhibitor of Polo-like Kinase 1.

The overexpression of the serine/threonine specific polo-like kinase 1 (Plk1) is associated with poor prognosis in many types of cancer. Consequently, Plk1 has emerged as a valid therapeutic target for anticancer drug design. Volasertib is a potent inhibitor of Plk1 that inhibits the proliferation of multiple human cancer cell lines by promoting cell cycle arrest at nanomolar concentrations. However, the risk of developing drug resistance, which is often associated with the overexpression of the ATP-binding cassette (ABC) transporter ABCB1 (P-glycoprotein), can present a therapeutic challenge for volasertib and many other therapeutic drugs. Although volasertib is highly effective against the proliferation of numerous cancer cell lines, we found that the overexpression of ABCB1 in cancer cells leads to cellular resistance to volasertib and reduces the level of volasertib-stimulated G2/M cell cycle arrest and subsequent onset of apoptosis. Furthermore, we demonstrate that volasertib competitively inhibits the function of ABCB1 and stimulates the basal ATPase activity of ABCB1 in a concentration-dependent manner, which is consistent with substrate transport by ABCB1. More importantly, we discovered that the coadministration of an inhibitor or drug substrate of ABCB1 restored the anticancer activity of volasertib in ABCB1-overexpressing cancer cells. In conclusion, the results of our study reveal that ABCB1 negatively affects the efficacy of volasertib and supports its combination with a modulator of ABCB1 to improve clinical responses.

Overexpression of human ABCB1 in cancer cells leads to reduced activity of GSK461364, a specific inhibitor of polo-like kinase 1.

Polo-like kinase 1 (Plk1) is a serine/threonine kinase involved in the regulation of mitosis and is overexpressed in many tumor types. Inhibition of Plk1 leads to cell cycle arrest, onset of apoptosis, and cell death, thus Plk1 has emerged as an important target for cancer treatment. GSK461364 is a potent inhibitor of Plk1 that inhibits the proliferation of multiple human cancer cell lines by promoting G2/M cell cycle arrest at low concentrations. However, as is the case for many therapeutic drugs, the risk of developing drug resistance to GSK461364 can present a therapeutic challenge to clinicians. Since the overexpression of ATP-binding cassette (ABC) drug transporter ABCB1 is one of the most common mechanisms of drug resistance, we aimed to investigate the effect of ABCB1 on the cellular efficacy of GSK461364. In this study, we observed a significantly reduced activity of GSK461364 in cells overexpressing human ABCB1. We showed that GSK461364 stimulates the ABCB1 ATPase activity and competitively inhibits ABCB1-mediated efflux of calcein-AM in a concentration-dependent manner. Moreover, as a way to assess the impact of ABCB1 on the efficacy of GSK461364, we evaluated the G2/M cell cycle arrest and apoptosis induced by GSK461364. We discovered that, by inhibiting the function of ABCB1, the reduced G2/M cell cycle arrest, apoptosis, and sensitivity to GSK461364 treatment in ABCB1-overexpressing cells can be significantly restored. In conclusion, in order to achieve a better therapeutic outcome, combination therapy of GSK461364 with a modulator of ABCB1 should be further investigated as a potential treatment approach.

Mechanism of Action of Acupotomy in Inhibiting Chondrocyte Apoptosis in Rabbits with KOA through the PI3K/Akt Signaling Pathway.

OBJECTIVE: We examined the effects of acupotomy on the PI3K/Akt signaling pathway to elucidate the mechanism of action of acupotomy on articular chondrocyte apoptosis among rabbits with knee osteoarthritis (KOA). METHODS: New Zealand rabbits were randomly assigned to a healthy control group, placebo group, acupotomy group, and drug group, with 10 rabbits in each group. Changes in chondrocytes were examined by hematoxylin and eosin staining, and articular chondrocyte apoptosis was measured by electron microscopy and immunofluorescence. The mRNA and protein expression levels of PI3K and Akt were measured by real-time quantitative PCR and Western blot. RESULTS: In contrast, less chromatin margination and clear and smooth nuclear envelope boundary were visible in the acupotomy group and drug group. The number of apoptotic chondrocytes in the knee joint of rabbits was significantly higher in the placebo group than that in the acupotomy group and drug group (P < 0.05). The acupotomy group had a nonsignificantly lower number of apoptotic chondrocytes than the drug group (P > 0.05). Furthermore, the mRNA and protein expression levels of PI3K and Akt were significantly higher in the acupotomy group and drug group than those in the placebo group (P < 0.05) and were closer to normal levels in the acupotomy group than those in the drug group (P < 0.05). PI3K and Akt expression levels were negatively correlated with chondrocyte apoptosis in the knee joint of rabbits in all groups. CONCLUSION: Inhibiting chondrocyte apoptosis in the knee joint of KOA rabbits by upregulating the PI3K/Akt signaling pathway may be a possible mechanism of acupotomy in treating KOA.

Molecular medicine of fragile X syndrome: based on known molecular mechanisms.

BACKGROUND: Extensive research on fragile X mental retardation gene knockout mice and mutant Drosophila models has largely expanded our knowledge on mechanism-based treatment of fragile X syndrome (FXS). In light of these findings, several clinical trials are now underway for therapeutic translation to humans. DATA SOURCES: Electronic literature searches were conducted using the PubMed database and ClinicalTrials.gov. The search terms included "fragile X syndrome", "FXS and medication", "FXS and therapeutics" and "FXS and treatment". Based on the publications identified in this search, we reviewed the neuroanatomical abnormalities in FXS patients and the potential pathogenic mechanisms to monitor the progress of FXS research, from basic studies to clinical trials. RESULTS: The pathological mechanisms of FXS were categorized on the basis of neuroanatomy, synaptic structure, synaptic transmission and fragile X mental retardation protein (FMRP) loss of function. The neuroanatomical abnormalities in FXS were described to motivate extensive research into the region-specific pathologies in the brain responsible for FXS behavioural manifestations. Mechanism-directed molecular medicines were classified according to their target pathological mechanisms, and the most recent progress in clinical trials was discussed. CONCLUSIONS: Current mechanism-based studies and clinical trials have greatly contributed to the development of FXS pharmacological therapeutics. Research examining the extent to which these treatments provided a rescue effect or FMRP compensation for the developmental impairments in FXS patients may help to improve the efficacy of treatments.

Human ATP-Binding Cassette transporters ABCB1 and ABCG2 confer resistance to CUDC-101, a multi-acting inhibitor of histone deacetylase, epidermal growth factor receptor and human epidermal growth factor receptor 2.

CUDC-101 is the first small-molecule inhibitor designed to simultaneously inhibit epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2) and histone deacetylase (HDAC) in cancer cells. Recently, in its first in human phase I study, CUDC-101 showed promising single agent activity against advanced solid tumors and favorable pharmacodynamic profile. However, the risk of developing drug resistance to CUDC-101 can still present a significant therapeutic challenge to clinicians in the future. One of the most common mechanisms of developing multidrug resistance (MDR) in cancer is associated with the overexpression of ATP-binding cassette (ABC) drug transporters ABCB1 and ABCG2. Together, they are able to reduce the efficacy and modify the pharmacological properties of anti-cancer agents, including many small molecule tyrosine kinase inhibitors (TKIs). Here, we have investigated the impact of ABCB1 and ABCG2 on the efficacy of CUDC-101 in human cancer cells. We revealed that although CUDC-101 has potent antiproliferative and proapoptotic activities against most cancer cell lines, the overexpression of ABCB1 or ABCG2 in cancer cells significantly reduced the activity of CUDC-101 against HDAC, EGFR and HER2, as well as its cytotoxicity and proapoptotic activity. Moreover, we showed that CUDC-101 modulated the function of both transporters without affecting the protein expression of either ABCB1 or ABCG2. More importantly, our study provides support for the rationale of combining CUDC-101 with modulators of ABC drug transporters to improve drug efficacy and overcome multidrug resistance associated with the overexpression of ABCB1 and ABCG2.

Human ABCB1 (P-glycoprotein) and ABCG2 mediate resistance to BI 2536, a potent and selective inhibitor of Polo-like kinase 1.

The overexpression of the serine/threonine specific Polo-like kinase 1 (Plk1) has been detected in various types of cancer, and thus has fast become an attractive therapeutic target for cancer therapy. BI 2536 is the first selective inhibitor of Plk1 that inhibits cancer cell proliferation by promoting G2/M cell cycle arrest at nanomolar concentrations. Unfortunately, alike most chemotherapeutic agents, the development of acquired resistance to BI 2536 is prone to present a significant therapeutic challenge. One of the most common mechanisms for acquired resistance in cancer chemotherapy is associated with the overexpression of ATP-binding cassette (ABC) transporters ABCB1, ABCC1 and ABCG2. Here, we discovered that overexpressing of either ABCB1 or ABCG2 is a novel mechanism of acquired resistance to BI 2536 in human cancer cells. Moreover, BI 2536 stimulates the ATPase activity of both ABCB1 and ABCG2 in a concentration-dependent manner, and inhibits the drug substrate transport mediated by these transporters. More significantly, the reduced chemosensitivity and BI 2536-mediated G2/M cell cycle arrest in cancer cells overexpressing either ABCB1 or ABCG2 can be significantly restored in the presence of selective inhibitor or other chemotherapeutic agents that also interact with ABCB1 and ABCG2, such as tyrosine kinase inhibitors nilotinib and lapatinib. Taken together, our findings indicate that in order to circumvent ABCB1 or ABCG2-mediated acquired resistance to BI 2536, a combined regimen of BI 2536 and inhibitors or clinically active drugs that potently inhibit the function of ABC drug transporters, should be considered as a potential treatment strategy in the clinic.