Recent Research Advances in Nano-Based Drug Delivery Systems for Local Anesthetics.

From a clinical perspective, local anesthetics have rather widespread application in regional blockade for surgery, postoperative analgesia, acute/chronic pain control, and even cancer treatments. However, a number of disadvantages are associated with traditional local anesthetic agents as well as routine drug delivery administration ways, such as neurotoxicity, short half-time, and non-sustained release, thereby limiting their application in clinical practice. Successful characterization of drug delivery systems (DDSs) for individual local anesthetic agents can support to achieve more efficient drug release and prolonged duration of action with reduced systemic toxicity. Different types of DDSs involving various carriers have been examined, including micromaterials, nanomaterials, and cyclodextrin. Among them, nanotechnology-based delivery approaches have significantly developed in the last decade due to the low systemic toxicity and the greater efficacy of non-conventional local anesthetics. Multiple nanosized materials, including polymeric, lipid (solid lipid nanoparticles, nanostructured lipid carriers, and nanoemulsions), metallic, inorganic non-metallic, and hybrid nanoparticles, offer a safe, localized, and long-acting solution for pain management and tumor therapy. This review provides a brief synopsis of different nano-based DDSs for local anesthetics with variable sizes and structural morphology, such as nanocapsules and nanospheres. Recent original research utilizing nanotechnology-based delivery systems is particularly discussed, and the progress and strengths of these DDSs are highlighted. A specific focus of this review is the comparison of various nano-based DDSs for local anesthetics, which can offer additional indications for their further improvement. All in all, nano-based DDSs with unique advantages provide a novel direction for the development of safer and more effective local anesthetic formulations.

Highly Efficient Photosensitizers with Molecular Vibrational Torsion for Cancer Photodynamic Therapy.

The development of highly effective photosensitizers (PSs) for photodynamic therapy remains a great challenge at present. Most PSs rely on the heavy-atom effect or the spin-orbit charge-transfer intersystem crossing (SOCT-ISC) effect to promote ISC, which brings about additional cytotoxicity, and the latter is susceptible to the interference of solvent environment. Herein, an immanent universal property named photoinduced molecular vibrational torsion (PVT)-enhanced spin-orbit coupling (PVT-SOC) in PSs has been first revealed. PVT is verified to be a widespread intrinsic property of quinoid cyanine (QCy) dyes that occurs on an extremely short time scale (10-10 s) and can be captured by transient spectra. The PVT property can provide reinforced SOC as the occurrence of ISC predicted by the El Sayed rules (1ππ*-3nπ*), which ensures efficient photosensitization ability for QCy dyes. Hence, QTCy7-Ac exhibited the highest singlet oxygen yield (13-fold higher than that of TCy7) and lossless fluorescence quantum yield (ΦF) under near-infrared (NIR) irradiation. The preeminent photochemical properties accompanied by high biosecurity enable it to effectively perform photoablation in solid tumors. The revelation of this property supplies a new route for constructing high-performance PSs for achieving enhanced cancer phototherapy.

Photothermal "nano-dot" reactivate "immune-hot" for tumor treatment via reprogramming cancer cells metabolism.

Cancer immunotherapy, despite its enormous application prospect, is trapped in the abnormal lactic acid metabolism of tumor cells that usually causes an immunosuppressive tumor microenvironment (ITM). Inducing immunogenic cell death (ICD) not only sensitizes cancer cells to carcer immunity, but also leads to a great increase in tumor-specific antigens. It improves tumor condition from "immune-cold" to "immune-hot". Herein, a near-infrared photothermal agent NR840 was developed and encapsulated into tumor-targeted polymer DSPE-PEG-cRGD and carried lactate oxidase (LOX) by electrostatic interaction, forming self-assembling "nano-dot" PLNR840 with high loading capacity for synergistic antitumor photo-immunotherapy. In this strategy, PLNR840 was swallowed by cancer cells, then dye NR840 was excited at 808 nm to generate heat inducing tumor cell necrosis, which further caused ICD. LOX could serve as a catalyst, reducing lactic acid efflux via regulation of cell metabolism. More importantly, the consumption of intratumoral lactic acid could substantially reverse ITM, including promoting the polarization of tumor-associated macrophages from M2 to M1 type, inhibiting the viability of regulatory T cells for sensitizing photothermal therapy (PTT). After the combination of αPD-L1 (programmed cell death protein ligand 1), PLNR840 restored CD8+ T-cell activity that thoroughly cleaned the pulmonary metastasis of breast cancer in 4T1 mouse model and cured hepatocellular carcinoma in Hepa1-6 mouse model. This study provided an effective PTT strategy to boost "immune-hot" and reprogrammed tumor metabolism for antitumor immunotherapy.

New Cy5 photosensitizers for cancer phototherapy: a low singlet-triplet gap provides high quantum yield of singlet oxygen.

Highly efficient triplet photosensitizers (PSs) have attracted increasing attention in cancer photodynamic therapy where photo-induced reactive oxygen species (ROSs, such as singlet oxygen) are produced via singlet-triplet intersystem crossing (ISC) of the excited photosensitizer to kill cancer cells. However, most PSs exhibit the fatal defect of a generally less-than-1% efficiency of ISC and low yield of ROSs, and this defect strongly impedes their clinical application. In the current work, a new strategy to enhance the ISC and high phototherapy efficiency has been developed, based on the molecular design of a thio-pentamethine cyanine dye (TCy5) as a photosensitizer. The introduction of an electron-withdrawing group at the meso-position of TCy5 could dramatically reduce the singlet-triplet energy gap (ΔE st) value (from 0.63 eV to as low as 0.14 eV), speed up the ISC process (τ ISC = 1.7 ps), prolong the lifetime of the triplet state (τ T = 319 µs) and improve singlet oxygen (1O2) quantum yield to as high as 99%, a value much higher than those of most reported triplet PSs. Further in vitro and in vivo experiments have shown that TCy5-CHO, with its efficient 1O2 generation and good biocompatibility, causes an intense tumor ablation in mice. This provides a new strategy for designing ideal PSs for cancer photo-therapy.

Selenium nanoparticles inhibit tumor metastasis in prostate cancer through upregulated miR-155-5p-related pathway.

Prostate cancer are the most common, malignant and lethal tumors in men, and the complexity of prostate cancer (CaP) is also due to the diverse metastasis profile. Selenium nanoparticles (SeNPs) have been reported to have potent antitumor activity, but whether it impacted the tumor metastasis is not fully clear. Here, we confirmed that SeNPs could inhibit the CaP cell migrations and invasions. Combined with our previous findings, we identified a series of microRNAs that could be upregulated significantly under SeNP treatment, among which miR-155-5p acts as a key component in mediating the SeNP-inhibited migration and invasion of CaP cells, through directly targeting IκB kinase ɛ and Sma- and Mad-related protein 2. The cell-based results were proved in xenograft mice modeling. These results have evidently signified the antitumor potential of SeNPs in the treatment of prostate cancer.

The Inhibitory Effect of Propylene Glycol Alginate Sodium Sulfate on Fibroblast Growth Factor 2-Mediated Angiogenesis and Invasion in Murine Melanoma B16-F10 Cells In Vitro.

Melanoma is one of the most malignant and aggressive types of cancer worldwide. Fibroblast growth factor 2 (FGF2) is one of the critical regulators of melanoma angiogenesis and metastasis; thus, it might be an effective anti-cancer strategy to explore FGF2-targeting drug candidates from existing drugs. In this study, we evaluate the effect of the marine drug propylene glycol alginate sodium sulfate (PSS) on FGF2-mediated angiogenesis and invasion. The data shows that FGF2 selectively bound to PSS with high affinity. PSS inhibited FGF2-mediated angiogenesis in a rat aortic ring model and suppressed FGF2-mediated invasion, but not the migration of murine melanoma B16-F10 cells. The further mechanism study indicates that PSS decreased the expression of activated matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9), and also suppressed their activity. In addition, PSS was found to decrease the level of Vimentin in B16-F10 cells, which is known to participate in the epithelial-mesenchymal transition. Notably, PSS did not elicit any changes in cancer cell viability. Based on the results above, we conclude that PSS might be a potential drug to regulate the tumor microenvironment in order to facilitate the recovery of melanoma patients.

Licochalcone A Protects the Blood-Milk Barrier Integrity and Relieves the Inflammatory Response in LPS-Induced Mastitis.

Background/Aims: Mastitis is an acute clinical inflammatory response. The occurrence and development of mastitis seriously disturb women's physical and mental health. Licochalcone A, a phenolic compound in Glycyrrhiza uralensis, has anti-inflammatory properties. Here, we examined the effect of licochalcone A on blood-milk barrier and inflammatory response in LPS-induced mice mastitis. Methods:In vivo, we firstly established mice models of mastitis by canal injection of LPS to mammary gland, and then detected the effect of licochalcone A on pathological indexes, inflammatory responses and blood-milk barrier in this model. In vivo, Mouse mammary epithelial cells (mMECs) were treated with licochalcone A prior to the incubation of LPS, and then the inflammatory responses, tight junction which is the basic structure of blood-milk barrier were analyzed. Last, we elucidated the anti-inflammatory mechanism by examining the activation of mitogen-activated protein kinase (MAPK) and AKT/NF-κB signaling pathways in vivo and in vitro. Result: The in vivo results showed that licochalcone A significantly decreased the histopathological impairment and the inflammatory responses, and improved integrity of blood-milk barrier. The in vitro results demonstrated that licochalcone A inhibited LPS-induced inflammatory responses and increase the protein levels of ZO-1, occludin, and claudin3 in mMECs. The in vivo and in vitro mechanistic study found that the anti-inflammatory effect of licochalcone A in LPS-induced mice mastitis was mediated by MAPK and AKT/NF-κB signaling pathways. Conclusions and Implications: Our experiments collectively indicate that licochalcone A protected against LPS-induced mice mastitis via improving the blood-milk barrier integrity and inhibits the inflammatory response by MAPK and AKT/NF-κB signaling pathways.

Hawthorn Extract Alleviates Atherosclerosis through Regulating Inflammation and Apoptosis Related Factors: An Experimental Study.

OBJECTIVE: To determine the effects of hawthorn extract on serum lipid levels, pathological changes in aortic atherosclerosis plaque, inflammatory factors, and apoptosis-related protein and mRNA expression in apolipoprotein E gene knockout (ApoE-/-) mice. METHODS: Thirty-six ApoE-/- mice were fed with a high-fat diet starting at the age of 8 weeks. Mice were randomly divided into 3 groups by a random number table including model group, hawthorn extract group, and simvastatin group, 12 mice in each group. Twelve 8-week-old C57BL/6 mice were fed a basic diet and served as control. The mice in the control and model groups were administered 0.2 mL saline daily, the mice in the hawthorn extract and simvastatin groups were administered with 50 mg/kg hawthorn extract or 5 mg/kg simvastatin daily for 16 weeks. After 16 weeks, plasma lipids including total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) were determined by an enzymatic assay. Aortic atherosclerotic lesions were observed by light microscopy, scanning and transmission electron microscopy, respectively. Plasma levels of monocyte chemoattractant protein-1 (MCP-1), interleukin-1ß (IL-1ß), adiponectin (APN), and hypersensitive C-reactive protein (hs-CRP) were measured by enzyme-linked immunosorbent assay (ELISA). Protein and mRNA expressions of Bax and Bcl-2 in the aorta were assessed by Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. RESULTS: Compared to the control group, the plasma levels of TC, TG and LDL-C were significantly increased and HDL-C were significantly decreased in the model group (P<0.01). Compared to the model group, treatment with hawthorn extract significantly decreased the plasma levels of TC, TG, and LDL-C and increased the plasma level of HDL-C in ApoE-/- mice (P<0.01). The levels of MCP-1, IL-1ß, and hs-CRP in the model group were significantly increased and APN was significantly decreased compared with the control group (P<0.01). Compared to the model group, treatment with hawthorn extract decreased the levels of MCP-1, IL-1ß, and hs-CRP and increased the APN level (P<0.01). Compared to the control group, the protein and mRNA expression of Bax in the model group were significantly increased and the expression of Bcl-2 was significantly decreased (P<0.01). Hawthorn extract also reduced the protein and mRNA expression of Bax and increased the Bcl-2 expression in the aorta (P<0.01). CONCLUSION: Hawthorn extract has anti-atherosclerosis and stabilizing unstable plaque effects. The mechanism may be related to the inflflammation and apoptosis signaling pathways.

Autologous and Nonautologous Blood Transfusion in Patients with Ruptured Ectopic Pregnancy and Severe Blood Loss.

BACKGROUND: There are some theoretical concerns for the use of intraoperative cell salvage (ICS) in patients with ectopic pregnancy. This study aimed to observe the impact of ICS on the coagulation function and clinical outcomes of patients with ruptured ectopic pregnancy and severe blood loss. METHODS: This was a retrospective study of 225 patients with ruptured ectopic pregnancy and severe blood loss treated at the Third Affiliated Hospital of Guangxi Medical University between January 2012 and May 2016. Patients were grouped according to ICS (n = 116) and controls (n = 109, allogenic transfusion and no transfusion). RESULTS: Compared with controls, patients with ICS had shorter hospitalization (P = 0.007), lower requirement for allogenic blood products (P < 0.001), and higher hemoglobin levels at discharge (P < 0.001). There were no complications/ adverse reactions. In the ICS group, hemoglobin at discharge (-6.5%, P = 0.002) and thrombin time (-3.7%, P = 0.002) were decreased 24 h after surgery, while 24 h APTT was increased (+4.6%, P < 0.001). In the control group, hemoglobin at discharge (-16.8%, P < 0.001) was decreased after surgery and 24 h APTT was increased (+2.4%, P = 0.045). At discharge, hemoglobin levels were higher in the ICS group (P < 0.001). CONCLUSION: ICS was associated with good clinical outcomes in patients with ruptured ectopic pregnancy and severe blood loss.

Molecular mechanisms of Bombyx batryticatus ethanol extract inducing gastric cancer SGC-7901 cells apoptosis.

Bombyx batryticatus is a traditional Chinese medicine. To understand apoptotic effect of B. batryticatus ethanol extract (BBE), we investigated the role of BBE in inducing apoptosis of human gastric cancer cells SGC-7901. Cells treated with BBE and apoptosis was assessed by methyl thiazolyl tetrazolium (MTT) assay, morphological changes, DNA fragmentation and flow cytometry assays. The expression of Bcl-2, Bax and P21 were evaluated by western blot analysis and real time polymerase chain reaction. MTT assay showed that the cytotoxicity of BBE extract on SGC-7901 cells was correlated with treatment time and concentration. After treatment with 6 mg/mL of BBE the microscopy showed that, the majority of SGC-7901 cells were obviously reduced, distorted and grew slowly. Annexin-V/propidium iodide double-staining assay emerge the early apoptosis and the late apoptosis after treatment with different times by laser confocal fluorescence microscopy and flow cytometer. Cell cycle analysis of SGC 79 cells showed that BBE induced cell cycle arrest in the G1 and G2 phases. DNA fragmentation indicated the trend of BBE inducing apoptosis on SGC-7901 cells. The qRT-PCR and western blot analysis indicated that the mRNA and protein expressions of Bax and P21 were significantly up-regulated whereas that of Bc1-2 was down-regulated after treatment with BBE for 24 h. Our results revealed a correlation between gene regulation and BBE-induced apoptosis, which might indicate the potential of BBE in cancer therapy.

Isolation and characterization of diterpene glycosides from Siegesbeckia pubescens.

Five new diterpenoid glycosides, siegesides A-E (1-5), along with the known compound darutoside (6) were isolated and characterized from the ethanol extract of Siegesbeckia pubescens. The structural elucidation of the isolates was accomplished by extensive HRESIMS and NMR analysis. Compounds 1 and 2 are epimers of 6. All isolates were evaluated for their inhibition on the migration of MB-MDA-231 breast cancer cells induced by the chemokine epithelial growth factor, and compound 2 showed superior inhibitory activities in comparison with the positive control drug with IC50 value of 0.27µM.

The efficiency of magnetic hyperthermia and in vivo histocompatibility for human-like collagen protein-coated magnetic nanoparticles.

Magnetic hyperthermia is a promising technique for the minimally invasive elimination of solid tumors. In this study, uniform magnetite nanoparticles (MNPs) with different particle sizes were used as a model system to investigate the size and surface effects of human-like collagen protein-coated MNPs (HLC-MNPs) on specific absorption rate and biocompatibility. It was found that these HLC-MNPs possess rapid heating capacity upon alternating magnetic field exposure compared to that of MNPs without HLC coating, irrespective of the size of MNPs. The significant enhancement of specific absorption rate is favorable for larger sized nanoparticles. Such behavior is attributed to the reduced aggregation and increased stability of the HLC-MNPs. By coating HLC on the surface of certain sized MNPs, a significant increase in cell viability (up to 2.5-fold) can be achieved. After subcutaneous injection of HLC-MNPs into the back of Kunming mice, it was observed that the inflammatory reaction hardly occurred in the injection site. However, there was a significant presence of phagocytes and endocytosis after the injection of nonconjugated counterparts. The overall strategy to fabricate HLC-MNPs can serve as a general guideline to address the current challenges in clinical magnetic hyperthermia, improved biocompatibility, and enhanced heating characteristics through protein coating.

Polydatin Attenuates H2O2-Induced Oxidative Stress via PKC Pathway.

Oxidative stress plays an important role in the pathogenesis of endothelial dysfunction, which is found to precede the development of diverse cardiovascular diseases (CVDs). The aim of this study was to observe the protective effects of PD against H2O2-induced oxidative stress injury (OSI) in human umbilical vein endothelial cells (HUVECs) and the possible mechanism of PD in OSI treatment. HUVECs were subjected to H2O2 in the absence or presence of PD. It turned out that PD improved cell viability and adhesive and migratory abilities, inhibited the release of lactate dehydrogenase (LDH) and reactive oxygen species (ROS), and elevated the content of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD). TUNEL, fluorometric assays, and Western blotting showed that OSI upregulated the apoptosis ratio, the activity of caspase-3 and the level of proapoptotic protein Bax and decreased the level of antiapoptotic protein Bcl-2. However, PD treatment partially reversed these damage effects and Protein Kinase C (PKC) activation by thymeleatoxin (THX) in turn eliminated the antiapoptotic effect of PD. Furthermore, PD attenuated the H2O2-induced phosphorylation of PKCs α and δ and increased the phosphorylation of PKC ε. Our results indicated that PD might exert protective effects against OSI through various interactions with PKC pathway.

Rituximab inhibits Kv1.3 channels in human B lymphoma cells via activation of FcγRIIB receptors.

Kv1.3 channels play an important role in modulating lymphocyte proliferation and apoptosis. We hypothesized that Kv1.3 channels in B lymphocytes might be regulated by rituximab, an antibody to CD20, a drug for treatments of B-cell lymphomas and autoimmune diseases. Using both whole-cell and cell-attached patch-clamp techniques, we found that rituximab inhibited Kv1.3 channels in Daudi human B lymphoma cells by promoting the channel inactivation at a concentration which was much greater than that required for activation of CD20. The effect of rituximab on Kv1.3 channels was abolished after selective blockade of FcγRIIB receptors with anti-FcγRIIB antibody. Western blot experiments showed that Daudi B cells expressed both Kv1.3 channel and the low affinity Fc receptor, FcγRIIB, which could be activated by the Fc region of rituximab. In contrast, normal lymphocytes expressed less Kv1.3 channels with faster inactivation. Confocal microscopy and flow cytometry data showed that rituximab induced apoptosis of Daudi B cells and that the effect was attenuated by blockade of FcγRIIB receptors and partially mimicked by inhibition of Kv1.3 channels. These results suggest that in addition to previously described complement-dependent cytotoxicity, rituximab also induces apoptosis of malignant B lymphocyte by stimulating FcγRIIB receptors and inhibiting Kv1.3 channels.

[Synergic effects of Danggui Buxue Decoction in reducing toxicity of cytoxan in tumor-bearing mice].

OBJECTIVE: To study the inhibitory effect of Danggui Buxue Tang (DBT), a compound traditional Chinese herbal medicine for supplementing blood, on tumor growth in tumor-bearing mice after inoculation of EL-4 cells, and its immune mechanism as well as its synergic effect in reducing toxicity of cytoxan (CTX). METHODS: Experiment was carried out in tumor-bearing mice after inoculation of EL-4 cells. The mice were randomly divided into four groups after 7 days of the inoculation: untreated group, DBT-treated group [24 g/(kg x d)], CTX-treated group [7.5 mg/(kg x d)] and DBT plus CTX-treated group, with another ten normal mice as control. Inhibitory rate of tumor growth, survival time, immune function and variability of blood cells were measured in the mice during the experiment. RESULTS: After treatment of relevant interventions for 15 days, the tumor in the DBT-treated group, CTX-treated group and DBT plus CTX-treated group grew slower than the untreated group (P<0.05). Murine survival time in the DBT-treated group, CTX-treated group and DBT plus CTX-treated group was lengthened as compared with that in the untreated group (P<0.05). Compared with the untreated group, all kinds of immune indexes in the DBT-treated group and DBT plus CTX-treated group were significantly improved (P<0.05), while the immune indexes in the CTX-treated group were decreased (P<0.05). Compared with the CTX-treated group, all kinds of immune indexes in the DBT plus CTX-treated group were significantly improved (P<0.05). CONCLUSIONS: DBT can enhance the immune function in tumor-bearing mice and the inhibitory effect of DBT on tumor growth is related to the enhanced immune response. DBT can also increase the therapeutic effects and reduce the side effects of CTX.

Regulation of the epithelial Na+ channel (ENaC) by phosphatidylinositides.

The epithelial Na(+) channel (ENaC) is an end-effector of diverse cellular signaling cascades, including those with phosphatidylinositide second messengers. Recent evidence also suggests that in some instances, phospatidylinositides can directly interact with ENaC to increase channel activity by increasing channel open probability and/or membrane localization. We review here findings relevant to regulation of ENaC by phosphatidylinositol 4,5-bisphosphate (PIP(2)) and phosphatidylinositol 3,4,5-triphosphate (PIP(3)). Similar to its actions on other ion channels, PIP(2) is permissive for ENaC openings having a direct effect on gating. The PIP(2) binding site in ENaC involved in this regulation is most likely localized to the NH(2) terminus of beta-ENaC. PIP(3) also affects ENaC gating but, rather than being permissive, augments open probability. The PIP(3) binding site in ENaC involved in this regulation is localized to the proximal region of the COOH terminus of gamma-ENaC just following the second transmembrane domain. In complementary pathways, PIP(3) also impacts ENaC membrane levels through both direct actions on the channel and via a signaling cascade involving phosphoinositide 3-OH kinase (PI3-K) and the aldosterone-induced gene product serum and glucocorticoid-inducible kinase. The putative PIP(3) binding site in ENaC involved in direct regulation of channel membrane levels has not yet been identified.

[Observation on effect of compound danshen droplet-pill combined with trimetazidine in treating senile unstable angina pectoris].

OBJECTIVE: To investigate the effect of compound Danshen Droplet-pill (DS) combined with trimetazidine (TMZ) in treating senile unstable angina pectoris (SUAP). METHODS: One hundred and twenty patients with SUAP were eaually and randomly divided into 2 groups, the treated group and the control group. Changes of angina, occurrence of arrhythmia, myocardial infarction and sudden death, myocardial ischemia in ECG and partial indexes of heart function were observed. RESULTS: The total effective rate in the treated group was 78.3%, while that in the control group was 53.3%, comparison of the two groups showed significant difference (P < 0.05). The incidence rate of arrhythmia in the two groups was 18.2% and 30.0% respectively and that of acute myocardial infarction and sudden death was 0 and 5.0% respectively, also showed significant difference between them (P < 0.05). Condition of myocardial ischemia revealed in ECG and partial indexes of heart function in the treated group were all improved to certain extent. Conclusion DS combined with TMZ is superior in treating SUAP.

Anionic phospholipids regulate native and expressed epithelial sodium channel (ENaC).

Using patch clamp techniques, we found that the epithelial sodium channel (ENaC) activity in the apical membrane of A6 distal nephron cells showed a sudden rundown beginning at 4 min after forming the inside-out configuration. This sudden rundown was prevented by addition of anionic phospholipids such as phosphatidylinositol 4,5-bisphosphate (PIP(2)), phosphatidylinositol 3,4,5-trisphosphate (PIP(3)), and phosphatidylserine (PS) to the "cytoplasmic" bath. Conversely, chelation of endogenous PIP(2) with anti-PIP(2) antibody, hydrolysis of PIP(2) with either exogenous phospholipase C (PLC) or activation of endogenous PLC by extracellular ATP, or application of the positively charged molecule, poly-L-lysine, accelerated channel rundown. However, neutral phosphatidylcholine had no effect on ENaC activity. By two-electrode voltage clamp recordings, we demonstrated that PIP(2) and PIP(3) significantly increased amiloride-sensitive current in Xenopus oocytes injected with cRNAs of rat alpha-, beta-, and gamma-ENaC. However, PIP(2) and PIP(3) did not affect surface expression of ENaC, indicating that PIP(2) and PIP(3) regulate ENaC at the level of the inner plasma membrane through a mechanism that is independent of ENaC trafficking. These data suggest that anionic phospholipids may mediate the regulation of ENaC by PLC- or phosphoinositide 3-kinase-coupled receptors.