Peripheral antinociception of a chalcone, flavokawin B and possible involvement of the nitric oxide/cyclic guanosine monophosphate/potassium channels pathway

Signal transduction of the insulin secretion induced by the chalcone analogue, (E)-3-(phenyl)-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one, and its role in glucose and lipid metabolism

A chalcone analogue, (E)-3-(phenyl)-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one (DMU 101), was synthesized using classic base catalysis and Claisen-Schmidt condensation, and then screened for its antidiabetic properties. The compound's effects on glucose and lipid metabolism were assayed in rats that were treated acutely and for a short time to elucidate its mechanism of action, evaluating glucose tolerance and lactate dehydrogenase activity in response to chalcone analogue administration. The chalcone's in vitro and ex vivo effects on glycogen, glucose, lipid and lipolysis were also investigated, as well as the mechanism by which it induces 45Ca2+ influx-mediated insulin secretion. The analogue (10 mg/kg) diminished glycemia, without inducing acute cell damage, increased glycogen content in the skeletal muscle and reduced serum triacylglycerol and total cholesterol, but did not alter high-density lipoprotein or low-density lipoprotein. Chalcone (10 μM) stimulated glucose uptake in the soleus muscle and did not modulate in vitro or ex vivo lipolysis. This analogue also increased insulin secretion by triggering calcium influx and blocking ATP-sensitive K+ channels and voltage-dependent calcium channels. However, it also modulated stored calcium via sarco/endoplasmic reticulum calcium ATPase (SERCA) and ryanodine receptor (RYR) activity. These findings indicate that this chalcone may induce cellular repolarization via a mechanism mediated by calcium-dependent potassium channels.

Dimethyl Itaconate Attenuates CFA-Induced Inflammatory Pain via the NLRP3/ IL-1β Signaling Pathway

Itaconate plays a prominent role in anti-inflammatory effects and has gradually been ushered as a promising drug candidate for treating inflammatory diseases. However, its significance and underlying mechanism for inflammatory pain remain unexplored. In the current study, we investigated the effects and mechanisms of Dimethyl Itaconate (DI, a derivative of itaconate) on Complete Freund’s adjuvant (CFA)-induced inflammatory pain in a rodent model. Here, we demonstrated that DI significantly reduced mechanical allodynia and thermal hyperalgesia. The DI-attenuated neuroinflammation was evident with the amelioration of infiltrative macrophages in peripheral sites of the hind paw and the dorsal root ganglion. Concurrently, DI hindered the central microglia activation in the spinal cord. Mechanistically, DI inhibited the expression of pro-inflammatory factors interleukin (IL)-1β and tumor necrosis factor alpha (TNF-α) and upregulated anti-inflammatory factor IL-10. The analgesic mechanism of DI was related to the downregulation of the nod-like receptor protein 3 (NLRP3) inflammasome complex and IL-1β secretion. This study suggested possible novel evidence for prospective itaconate utilization in the management of inflammatory pain.

Melanogenic Inhibition and Toxicity Assessment of Flavokawain A and B on B16/F10 Melanoma Cells and Zebrafish (Danio rerio)

Excessive production of melanin implicates hyperpigmentation disorders. Flavokawain A (FLA) and flavokawain B (FLB) have been reported with anti-melanogenic activity, but their melanogenic inhibition and toxicity effects on the vertebrate model of zebrafish are still unknown. In the present study, cytotoxic as well as melanogenic effects of FLA and FLB on cellular melanin content and tyrosinase activity were evaluated in α-MSH-induced B16/F10 cells. Master regulator of microphthalmia-associated transcription factor (Mitf) and the other downstream melanogenic-related genes were verified via quantitative real time PCR (qPCR). Toxicity assessment and melanogenesis inhibition on zebrafish model was further observed. FLA and FLB significantly reduced the specific cellular melanin content by 4.3-fold and 9.6-fold decrement, respectively in α-MSH-induced B16/F10 cells. Concomitantly, FLA significantly reduced the specific cellular tyrosinase activity by 7-fold whilst FLB by 9-fold. The decrement of melanin production and tyrosinase activity were correlated with the mRNA suppression of Mitf which in turn down-regulate Tyr, Trp-1 and Trp-2. FLA and FLB exhibited non-toxic effects on the zebrafish model at 25 and 6.25 µM, respectively. Further experiments on the zebrafish model demonstrated successful phenotype-based depigmenting activity of FLA and FLB under induced melanogenesis. To sum up, our findings provide an important first key step for both of the chalcone derivatives to be further studied and developed as potent depigmenting agents.

Design, Synthesis and Docking Studies of Flavokawain B Type Chalcones and Their Cytotoxic Effects on MCF-7 and MDA-MB-231 Cell Lines

Flavokawain B (1) is a natural chalcone extracted from the roots of Piper methysticum, and has been proven to be a potential cytotoxic compound. Using the partial structure of flavokawain B (FKB), about 23 analogs have been synthesized. Among them, compounds 8, 13 and 23 were found in new FKB derivatives. All compounds were evaluated for their cytotoxic properties against two breast cancer cell lines, MCF-7 and MDA-MB-231, thus establishing the structure–activity relationship. The FKB derivatives 16 (IC₅₀ = 6.50 ± 0.40 and 4.12 ± 0.20 μg/mL), 15 (IC₅₀ = 5.50 ± 0.35 and 6.50 ± 1.40 μg/mL) and 13 (IC₅₀ = 7.12 ± 0.80 and 4.04 ± 0.30 μg/mL) exhibited potential cytotoxic effects on the MCF-7 and MDA-MB-231 cell lines. However, the methoxy group substituted in position three and four in compound 2 (IC₅₀ = 8.90 ± 0.60 and 6.80 ± 0.35 μg/mL) and 22 (IC₅₀ = 8.80 ± 0.35 and 14.16 ± 1.10 μg/mL) exhibited good cytotoxicity. The lead compound FKB (1) showed potential cytotoxicity (IC₅₀ = 7.70 ± 0.30 and 5.90 ± 0.30 μg/mL) against two proposed breast cancer cell lines. It is evident that the FKB skeleton is unique for anticancer agents, additionally, the presence of halogens (Cl and F) in position 2 and 3 also improved the cytotoxicity in FKB series. These findings could help to improve the future drug discovery process to treat breast cancer. A molecular dynamics study of active compounds revealed stable interactions within the active site of Janus kinase. The structures of all compounds were determined by ¹H-NMR, EI-MS, IR and UV and X-ray crystallographic spectroscopy techniques.

Zerumbone Alleviates Neuropathic Pain through the Involvement of l-Arginine-Nitric Oxide-cGMP-K⁺ ATP Channel Pathways in Chronic Constriction Injury in Mice Model

The present study investigates the involvement of the l-arginine-Nitric Oxide-cGMP-K⁺ ATP pathways responsible for the action of anti-allodynic and antihyperalgesic activities of zerumbone in chronic constriction injury (CCI) induced neuropathic pain in mice. The role of l-arginine-NO-cGMP-K⁺ was assessed by the von Frey and the Randall-Selitto tests. Both allodynia and hyperalgesia assessments were carried out on the 14th day post CCI, 30 min after treatments were given for each respective pathway. Anti-allodynic and antihyperalgesic effects of zerumbone (10 mg/kg, i.p) were significantly reversed by the pre-treatment of l-arginine (10 mg/kg), 1H [1,2,4]Oxadiazole[4,3a]quinoxalin-1-one (ODQ), a soluble guanosyl cyclase blocker (2 mg/kg i.p.) and glibenclamide (ATP-sensitive potassium channel blocker) (10 mg/kg i.p.) (p < 0.05). Taken together, these results indicate that systemic administration of zerumbone produces significant anti-allodynic and antihyperalgesic activities in neuropathic pain in mice possibly due to involvement of the l-arginine-NO-cGMP-PKG-K⁺ ATP channel pathways in CCI model.

Antinociceptive Effect of 3-(2,3-Dimethoxyphenyl)-1-(5-methylfuran-2-yl)prop-2-en-1-one in Mice Models of Induced Nociception

The antinociceptive effects produced by intraperitoneal administration of a novel synthetic chalcone, 3-(2,3-dimethoxyphenyl)-1-(5-methylfuran-2-yl)prop-2-en-1-one (DMFP), were investigated in several mouse models of induced nociception. The administration of DMFP (0.1, 0.5, 1.0 and 5.0 mg/kg) produced significant attenuation on the acetic acid-induced abdominal-writhing test. It also produced a significant increase in response latency time in the hot-plate test and a marked reduction in time spent licking the injected paw in both phases of the formalin-induced paw-licking test. In addition, it was also demonstrated that DMFP exhibited significant inhibition of the neurogenic nociceptive response induced by intraplantar injections of capsaicin and glutamate. Moreover, the antinociceptive effect of DMFP in the acetic acid-induced abdominal-writhing test and the hot-plate test was not antagonized by pretreatment with a non-selective opioid receptor antagonist, naloxone. Finally, DMFP did not show any toxic effects and/or mortality in a study of acute toxicity and did not interfere with motor coordination during the Rota-rod test. Our present results show that DMFP exhibits both peripheral and central antinociceptive effects. It was suggested that its peripheral antinociceptive activity is associated with attenuated production and/or release of NO and various pro-inflammatory mediators, while central antinociceptive activity seems to be unrelated to the opioidergic system, but could involve, at least in part, an interaction with the inhibition of capsaicin-sensitive fibers and the glutamatergic system.

Antinociceptive Effect of Vardenafil on Carrageenan-Induced Hyperalgesia in Rat: involvement of Nitric Oxide/Cyclic Guanosine Monophosphate/Calcium Channels Pathway

In this study, we aimed to investigate the peripheral antinociception effects of specific phosphodiesterase 5 (PDE-5) inhibitor vardenafil on carrageenan-induced nociception in rats, and the role of calcium besides the L-arginine- nitric oxide (NO)- cyclic guanosine monophophate (cGMP) pathway in these effects. Hyperalgesia was induced by the intraplantar injection of 0.1 mL fresh carrageenan solution to right hind-paw whereas, saline as a vehicle of carrageenan was injected to the left paw. This procedure was used for measuring mechanic nociception pressure via an analgesimeter. Pressure which produced nociception was measured before (0 minute) and after(15, 30, 60 and 120 minutes) carrageenan injection. Local administration of vardenafil produced a dose-dependent antinociceptive effect. Pretreatment with N(W)-nitro-L-arginine methyl ester (L-NAME, nitric oxide synthase inhibitor), oxadiazolo (4, 3, a) quinoxalin -1-one (ODQ, inhibitor of guanylyl cyclase) or A23187 (calcium ionophore) decreased the effect of vardenafil. In contrast, L-arginine (nitric oxide donor) seemed to potentiate the vardenafil-induced antinociception. Our results suggest that phosphodiesterase type-5 inhibitor vardenafil may offer a new therapeutic tool to treat pain. It's effect was probably result from L-arginine/NO-cGMP pathway activation and Ca + 2 channels are also involved.