Jinlong Qi

Design, synthesis and biological activity of pyrazolo(1,5-a)pyrimidin-7(4H)-ones as novel Kv7/KCNQ potassium channel activators

Voltage-gated Kv7/KCNQ/M-potassium channels play a pivotal role in controlling neuronal excitability. Genetic reduction of KCNQ channel activity as a result of mutations causes various human diseases such as epilepsy and arrhythmia. Therefore, discovery of small molecules that activate KCNQ channels is an important strategy for clinical intervention of membrane excitability related disorders. In this study, a series of pyrazolo[1,5-a]pyrimidin-7(4H)-ones (PPOs) have been found to be novel activators (openers) of KCNQ2/3 potassium channels through high-throughput screening by using atomic absorption rubidium efflux assay. Based on structure-activity relationship (SAR), the substituted PPOs have been optimized. The 5-(2,6-dichloro-5-fluoropyridin-3-yl)-3-phenyl-2-(trifluoromethyl) pyrazolo[1,5-a]pyrimidin-7(4H)-one (17) was identified as a novel, potent, and selective KCNQ2/3 potassium channel opener by patch-clamp recording assay.

Local GABAergic signaling within sensory ganglia controls peripheral nociceptive transmission

The integration of somatosensory information is generally assumed to be a function of the central nervous system (CNS). Here we describe fully functional GABAergic communication within rodent peripheral sensory ganglia and show that it can modulate transmission of pain-related signals from the peripheral sensory nerves to the CNS. We found that sensory neurons express major proteins necessary for GABA synthesis and release and that sensory neurons released GABA in response to depolarization. In vivo focal infusion of GABA or GABA reuptake inhibitor to sensory ganglia dramatically reduced acute peripherally induced nociception and alleviated neuropathic and inflammatory pain. In addition, focal application of GABA receptor antagonists to sensory ganglia triggered or exacerbated peripherally induced nociception. We also demonstrated that chemogenetic or optogenetic depolarization of GABAergic dorsal root ganglion neurons in vivo reduced acute and chronic peripherally induced nociception. Mechanistically, GABA depolarized the majority of sensory neuron somata, yet produced a net inhibitory effect on the nociceptive transmission due to the filtering effect at nociceptive fiber T-junctions. Our findings indicate that peripheral somatosensory ganglia represent a hitherto underappreciated site of somatosensory signal integration and offer a potential target for therapeutic intervention.

Differentiation of genuine Inula britannica L. and substitute specimens based on the determination of 15 components using LC-MS/MS and principal components analysis.

The aim of this study was to investigate the chemical differences between genuine Inula britannica L. (I. britannica) and substitute specimens. A linear ion trap LC-MS/MS analytical method has been developed for the identification and quantification of 15 major components from I. britannica. Data acquisition was performed in multiple-reaction-monitoring transitions mode followed by an information-dependent acquisition using the enhanced product ion (EPI) scan in one run. The target compounds were further identified and confirmed using an EPI spectral library. The determination results of 45 batches of samples were then analysed and classified by principal component analysis (PCA). The content of 11 components could be used to distinguish the two official Flos Inulae species (I. britannica and Inula japonica) from unofficial species (Inula hupehensis), and the content of 3 components could be used to differentiate the two official species.

The Role of Potassium Channel Activation in Celecoxib-Induced Analgesic Action

Background and Purpose Celecoxib (CXB) is a widely prescribed COX-2 inhibitor used clinically to treat pain and inflammation. Recently, COX-2 independent mechanisms have been described to be the targets of CXB. For instance, ion channels such as the voltage-gated sodium channel, L-type calcium channel, Kv2.1, Kv1.5, Kv4.3 and HERG potassium channel were all reported to be inhibited by CXB. Our recent study revealed that CXB is a potent activator of Kv7/M channels. M currents expressed in dorsal root ganglia play an important role in nociception. Our study was aimed at establishing the role of COX-2 independent M current activation in the analgesic action of CXB. Methods and Results We compared the effects of CXB and its two structural analogues, unmethylated CXB (UMC) and 2,5-dimethyl-CXB (DMC), on Kv7/M currents and pain behavior in animal models. UMC is a more potent inhibitor of COX-2 than CXB while DMC has no COX-2 inhibiting activity. We found that CXB, UMC and DMC concentration-dependently activated Kv7.2/7.3 channels expressed in HEK293 cells and the M-type current in dorsal root ganglia neurons, negatively shifted I–V curve of Kv7.2/7.3 channels, with a potency and efficiency inverse to their COX-2 inhibitory potential. Furthermore, CXB, UMC and DMC greatly reduced inflammatory pain behavior induced by bradykinin, mechanical pain behavior induced by stimulation with von Frey filaments and thermal pain behavior in the Hargreaves test. CXB and DMC also significantly attenuated hyperalgesia in chronic constriction injury neuropathic pain. Conclusion CXB, DMC and UMC are openers of Kv7/M K+ channels with effects independent of COX-2 inhibition. The analgesic effects of CXBs on pain behaviors, especially those of DMC, suggest that activation of Kv7/M K+ channels may play an important role in the analgesic action of CXB. This study strengthens the notion that Kv7/M K+ channels are a potential target for pain treatment.

Activation of KCNQ2/3 Potassium Channels by Novel Pyrazolo[1,5-a]pyrimidin-7(4H)-One Derivatives

The voltage-gated M-type potassium channel, encoded mainly by the KCNQ2/3 genes, plays an important role in the control of neuronal excitability. Mutations in the KCNQ2 gene lead to a form of neonatal epilepsy in humans termed ‘benign familial neonatal convulsions’, which is characterized by hyperexcitability of neurons. KCNQ openers or activators are expected to decrease the firing of overactive neurons and are thus conducive to the treatment of epilepsy and pain. Here, we report that four novel synthesized derivatives of pyrazolo[1,5-a]pyrimidin-7(4H)-one (PPO) named QO-26, QO-28, QO-40 and QO-41 potently augmented KCNQ2/3 channels expressed in Chinese hamster ovary cells and shifted the half-maximal activation voltage (V1/2) in the hyperpolarizing direction. The V1/2 was negatively shifted in a concentration-dependent manner. The compounds markedly slowed both KCNQ2/3 channel activation and deactivation kinetics. Structure-activity relationship studies suggest that trifluoromethyl at the C-2 position, phenyl or naphthyl at the C-3 position, and trifluoromethyl or chloromethyl at the C-5 position are essential for the activity. These results suggest the four PPO derivatives act as KCNQ2/3 channel openers, providing a new dimension for the design and development of more potent channel openers.

Redox-Dependent Modulation of T-Type Ca2+ Channels in Sensory Neurons Contributes to Acute Anti-Nociceptive Effect of Substance P

Abstract Aims: Neuropeptide substance P (SP) is produced and released by a subset of peripheral sensory neurons that respond to tissue damage (nociceptors). SP exerts excitatory effects in the central nervous system, but peripheral SP actions are still poorly understood; therefore, here, we aimed at investigating these peripheral mechanisms. Results: SP acutely inhibited T-type voltage-gated Ca2+ channels in nociceptors. The effect was mediated by neurokinin 1 (NK1) receptor-induced stimulation of intracellular release of reactive oxygen species (ROS), as it can be prevented or reversed by the reducing agent dithiothreitol and mimicked by exogenous or endogenous ROS. This redox-mediated T-type Ca2+ channel inhibition operated through the modulation of CaV3.2 channel sensitivity to ambient zinc, as it can be prevented or reversed by zinc chelation and mimicked by exogenous zinc. Elimination of the zinc-binding site in CaV3.2 rendered the channel insensitive to SP-mediated inhibition. Importantly, peripherally applied SP significantly reduced bradykinin-induced nociception in rats in vivo; knock-down of CaV3.2 significantly reduced this anti-nociceptive effect. This atypical signaling cascade shared the initial steps with the SP-mediated augmentation of M-type K+ channels described earlier. Innovation: Our study established a mechanism underlying the peripheral anti-nociceptive effect of SP whereby this neuropeptide produces ROS-dependent inhibition of pro-algesic T-type Ca2+ current and concurrent enhancement of anti-algesic M-type K+ current. These findings will lead to a better understanding of mechanisms of endogenous analgesia. Conclusion: SP modulates T-type channel activity in nociceptors by a redox-dependent tuning of channel sensitivity to zinc; this novel modulatory pathway contributes to the peripheral anti-nociceptive effect of SP. Antioxid. Redox Signal. 25, 233–251.

A New Limonoid from Xylocarpus granatum

A new limonoid, named xylocartin C (1), was isolated from the seeds of Xylocarpus granatum and its structure was elucidated on the basis of one- and two-dimensional NMR (including 1H, 13C NMR, DEPT, 1H–1H COSY, HSQC, HMBC, and NOESY).

Chemical Constituents of Xylocarpus granatum

Xylocarpus granatum K. D. Koenig, a marine mangrove plant distributed mainly along the seashore along the Indian Ocean and in Southeast Asia, is used in folk medicine in Southeast Asia for the treatment of diarrhea, cholera, and fever diseases such as malaria, and also as an antifeedant [1, 2]. Since the first limonoid, gedunin, was reported from this plant [3], the unique structural patterns of limonoids have attracted considerable attention from medicinal chemists as well as chemical biologists because of their fascinating structural diversity and important biological activities. As a result, more than 50 limonoid derivatives have been isolated from X. granatum, and they have been classified into phragmalin, mexicanolide, obacunol, and andirobin types [4–9]. In our effort to study the biological activity of natural products used as the lead molecule of drugs from Chinese medicinal plants, nine limonoid compounds and two steroids were isolated from a dichloromethane extract of the seed of Xylocarpus granatum. We report herein the isolation and structural elucidation of all these compounds. From a dichloromethane extract of the seed of X. granatum, xylomexicanin A (1) [10], xylogranatin D (2) [7], hainangranatumin A (3) [11], xylogranatin C (4) [7], hainangranatumin C (5) [11], xylocarpin H (6) [9], xyloccensin K (7) [12], piscidinol G (8) [13], xylocarpin G (9) [9], hydroxydammarenone-II (10), and stigmasterol (11) were isolated and purified by repeated chromatography over a silica gel column. The structure of every compound was postulated on the basis of spectroscopic analysis. Hydroxydammarenone-II (10) from this genus is reported for the first time here.

Granaxylocartin A, New Limonoid from the Seeds of Xylocarpus granatum

A new limonoid, named granaxylocartin A (1), was isolated from the seeds of Xylocarpus granatum, and the structure was elucidated on the basis of one- and two-dimensional NMR (including 1H, 13C NMR, DEPT, 1H–1H COSY, HSQC, HMBC, and NOESY).