Zhengyu Cao

The protective effects of Ribes diacanthum Pall on cisplatin-induced nephrotoxicity in mice.

ETHNOPHARMACOLOGICAL RELEVANCE Ribes diacanthum Pall. (Saxifragaceae), a Mongolian folk medicinal plant, was used to treat urinary system diseases. The present work aims to investigate the protective effects of Ribes diacanthum Pall (RDP) against cisplatin-induced nephrotoxicity. METHODS The renal injury was modeled by intraperitoneal injection of cisplatin for 5 consecutive days (5 mg/kg). Nephroprotection of RDP was investigated by oral administration of RDP aqueous extract at a daily dose of 40 mg/kg for 14 consecutive days, starting 7 days prior to cisplatin administration. RESULTS We demonstrated that pretreatment with RDP aqueous extract protected the mice from death induced by cisplatin administration. RDP treatment also significantly reduced blood urea nitrogen (BUN) and serum creatinine (Cr) levels observed in cisplatin-administrated mice. Histopathological analysis demonstrated that RDP administration protected cisplatin-induced renal tubular cell apoptosis. Further western blotting analysis revealed that RDP significantly reversed cisplatin-increased expression levels of cleaved-Caspase-3, Bax and cisplatin-decreased expression level of Bcl-2 in renal tissue. Finally, RDP markedly enhanced enzyme activities of reduced superoxide dismutase (SOD), Heme oxygenase 1 (HO-1) and catalase (CAT), suppressed lipid peroxidation as well as reactive oxygen species (ROS) production. CONCLUSION We concluded that RDP displayed nephroprotective effects against cisplatin-induced renal tubular cell apoptosis, possibly associated with both enhanced antioxidase activity and suppressed ROS generation. Given the major nephrotoxicity of cisplatin cancer chemotherapy, RDP might be a potential candidate for neoadjuvant chemotherapy.

Development of a Rapid Throughput Assay for Identification of hNav1.7 Antagonist Using Unique Efficacious Sodium Channel Agonist, Antillatoxin.

Voltage-gated sodium channels (VGSCs) are responsible for the generation of the action potential. Among nine classified VGSC subtypes (Nav1.1–Nav1.9), Nav1.7 is primarily expressed in the sensory neurons, contributing to the nociception transmission. Therefore Nav1.7 becomes a promising target for analgesic drug development. In this study, we compared the influence of an array of VGSC agonists including veratridine, BmK NT1, brevetoxin-2, deltamethrin and antillatoxin (ATX) on membrane depolarization which was detected by Fluorescence Imaging Plate Reader (FLIPR) membrane potential (FMP) blue dye. In HEK-293 cells heterologously expressing hNav1.7 α-subunit, ATX produced a robust membrane depolarization with an EC50 value of 7.8 ± 2.9 nM whereas veratridine, BmK NT1, and deltamethrin produced marginal response. Brevetoxin-2 was without effect on membrane potential change. The ATX response was completely inhibited by tetrodotoxin suggesting that the ATX response was solely derived from hNav1.7 activation, which was consistent with the results where ATX produced a negligible response in null HEK-293 cells. Six VGSC antagonists including lidocaine, lamotrigine, phenytoin, carbamazepine, riluzole, and 2-amino-6-trifluoromethylthiobenzothiazole all concentration-dependently inhibited ATX response with IC50 values comparable to that reported from patch-clamp experiments. Considered together, we demonstrate that ATX is a unique efficacious hNav1.7 activator which offers a useful probe to develop a rapid throughput screening assay to identify hNav1.7 antagonists.

Polycycloiridals with a Cyclopentane Ring from Iris tectorum

Six new iridal-type triterpenoids containing an unprecedented cyclopentane ring, polycycloiridals E-J (1-6), were isolated from a large-scale re-extraction of Iris tectorum. A possible biosynthesis pathway is postulated. The known spirioiridotectal D (7) was also obtained in the current investigation, and its structure was unequivocally defined using X-ray diffraction data. Compound 7 suppressed LPS-activated NO production in the BV2 cell line with an IC50 value of 0.54 μM.

Selective Voltage-Gated Sodium Channel Peptide Toxins from Animal Venom: Pharmacological Probes and Analgesic Drug Development

Voltage-gated sodium channels (Navs) play critical roles in action potential generation and propagation. Nav channelopathy as well as pathological sensitization contribute to allodynia and hyperalgesia. Recent evidence has demonstrated the significant roles of Nav subtypes (Nav1.3, 1.7, 1.8, and 1.9) in nociceptive transduction, and therefore these Navs may represent attractive targets for analgesic drug discovery. Animal toxins are structurally diverse peptides that are highly potent yet selective on ion channel subtypes and therefore represent valuable probes to elucidate the structures, gating properties, and cellular functions of ion channels. In this review, we summarize recent advances on peptide toxins from animal venom that selectively target Nav1.3, 1.7, 1.8, and 1.9, along with their potential in analgesic drug discovery.

Modification of distinct ion channels differentially modulates Ca 2+ dynamics in primary cultured rat ventricular cardiomyocytes

Primary cultured cardiomyocytes show spontaneous Ca2+ oscillations (SCOs) which not only govern contractile events, but undergo derangements that promote arrhythmogenesis through Ca2+ -dependent mechanism. We systematically examined influence on SCOs of an array of ion channel modifiers by recording intracellular Ca2+ dynamics in rat ventricular cardiomyocytes using Ca2+ specific fluorescence dye, Fluo-8/AM. Voltage-gated sodium channels (VGSCs) activation elongates SCO duration and reduces SCO frequency while inhibition of VGSCs decreases SCO frequency without affecting amplitude and duration. Inhibition of voltage-gated potassium channel increases SCO duration. Direct activation of L-type Ca2+ channels (LTCCs) induces SCO bursts while suppressing LTCCs decreases SCO amplitude and slightly increases SCO frequency. Activation of ryanodine receptors (RyRs) increases SCO duration and decreases both SCO amplitude and frequency while inhibiting RyRs decreases SCO frequency without affecting amplitude and duration. The potencies of these ion channel modifiers on SCO responses are generally consistent with their affinities in respective targets demonstrating that modification of distinct targets produces different SCO profiles. We further demonstrate that clinically-used drugs that produce Long-QT syndrome including cisapride, dofetilide, sotalol, and quinidine all induce SCO bursts while verapamil has no effect. Therefore, occurrence of SCO bursts may have a translational value to predict cardiotoxicants causing Long-QT syndrome.

Activation of sodium channel by a novel α-scorpion toxin, BmK NT2, stimulates ERK1/2 and CERB phosphorylation through a Ca2+ dependent pathway in neocortical neurons

Neuronal excitability controls the expression of a variety of genes and proteins and therefore regulates neurite outgrowth and synapse formation, fundamental physiological processes controlling learning and memory. Scorpion venom contains many neurotoxins which alter ion channel activities that influence neuronal excitability. In this study, a novel scorpion peptide termed BmK NT2 was purified from venom of Chinese scorpion Buthus martensii Karsch by combining mass spectrum mapping and intracellular Ca2+ concentration measurement in primary cultured neocortical neurons. Electrophysiological experiments demonstrated that BmK NT2 concentration-dependently delayed inactivation of voltage-gated sodium channels (VGSCs) with an EC50 value of 0.91μM, and shifted the steady-state activation and inactivation of VGSCs to hyperpolarized direction. The effects of BmK NT2 on electrophysiological characteristics of VGSCs were similar to that of α-scorpion toxins. BmK NT2 altered Ca2+ dynamics and increased phosphorylation of extracellular-regulated protein kinases (ERK) 1/2 and cAMP-response element binding (CREB) proteins, which were eliminated by the VGSC blocker, tetrodotoxin. These data demonstrate that BmK NT2 is a novel VGSC α-scorpion toxin which is sufficient to increase the phosphorylation of ERK1/2 and CREB proteins, suggesting that modulation of VGSC function by α-scorpion toxin exerts neurotrophic effect in primary cultured neocortical neurons.

Ribemansides A and B, TRPC6 Inhibitors from Ribes manshuricum That Suppress TGF-β1-Induced Fibrogenesis in HK-2 Cells

Two new acylated β-hydroxynitrile glycosides, ribemansides A (1) and B (2), were isolated from the aerial parts of Ribes manshuricum. Their structures were elucidated by comprehensive spectroscopic analysis. Ribemansides A and B inhibited transforming growth factor β1 (TGF-β1)-induced expression of α-smooth muscle actin, fibronectin release, and changes in cell morphology in the human proximal tubular epithelial cell line (human kidney-2, HK-2). Further biological evaluation demonstrated that both 1 and 2 inhibit the activity of canonical transient receptor potential cation channel 6 (TRPC6), with IC50 values of 24.5 and 25.6 μM, respectively. The antifibrogenic effect of these compounds appears to be mediated through TRPC6 inhibition, since the TRPC6 inhibitor, SAR7334, also suppressed TGF-β1-induced fibrogenesis in HK-2 cells.

Ribes diacanthum Pall (RDP) ameliorates UUO-induced renal fibrosis via both canonical and non-canonical TGF-β signaling pathways in mice

ETHNOPHARMACOLOGICAL RELEVANCE Ribes diacanthum Pall (RDP), a folk medicine, has been widely used in Mongolia to treat urinary system diseases. AIM OF THE STUDY To investigate the effectiveness of RDP on unilateral ureteral obstruction (UUO)-induced renal interstitial fibrosis and the underlying mechanisms. MATERIALS AND METHODS A total of 60 mice were randomly divided into six groups: sham group, sham plus RDP (40 mg/kg) group, UUO model group, and UUO model plus RDP (10, 20 or 40 mg/kg) groups. After surgery, aqueous extract of RDP were administrated intragastrically (i.g) daily for a week and ipsilateral kidneys were collected seven days after surgery. Levels of blood urea nitrogen (BUN) and serum creatinine (Scr) were detected to reflect the kidney injury. Hematoxylin & eosin and Massons trichrome staining were used to evaluate the kidney morphological changes and fibrosis, respectively. ELISA was used to examine the levels of pro-inflammatory cytokines. Immunohistochemistry, western blot and PCR were used to examine the expression levels of key proteins involved in transforming growth factor (TGF-β)/Smad and mitogen-activated protein kinase (MAPK) signaling pathways. RESULTS RDP treatment attenuates the level of BUN and kidney fibrosis in UUO mice, decreases the expressions of interleukin-6, tumor necrosis factor-α, Interleukin-1α, TGF-β1, monocyte chemotactic protein-1, α-smooth muscle actin, collagen I, fibronectin, and vimentin, while increases the expressions of E-cadherin and hepatocyte growth factor. Moreover, RDP administration significantly decreases the levels of p-Smad2/3, p-ERK1/2, p-p38 and p-JNK, while increases the expression level of Smad7 in UUO models. CONCLUSION These data demonstrate that RDP ameliorates renal fibrosis through TGF-β/Smad and MAPK pathways in a UUO mouse model.

Iritectol G, a novel iridal-type triterpenoid from Iris tectorum displays anti-epileptic activity in vitro through inhibition of sodium channels

Iritectol G, a novel iridal-type triterpenoid containing an uncommon tetrahydrofuran moiety, was isolated from the rhizomes of Iris tectorum. The structure was elucidated by comprehensive spectroscopic analysis. Iritectol G inhibited spontaneous and 4-aminopyridine-evoked calcium oscillations in primary cultured neocortical neurons with IC50 values of 8.2μM and 12.5μM, respectively. Further electrophysiological study demonstrated that iritectol G preferred to interact with inactivated state of voltage-gated sodium channel with an IC50 value of 7.0μM. These data demonstrated that iritectol G was a novel sodium channel inhibitor.