Ca2+ entry via TRPC channels is necessary for thrombin-induced NF-kappaB activation in endothelial cells through AMP-activated protein kinase and protein kinase Cdelta

Naringenin: its chemistry and roles in neuroprotection

According to epidemiological research, as the population ages, neurological illnesses are becoming a bigger issue. Despite improvements in the treatment of these diseases, there are still widespread worries about how to find a long-lasting remedy. Several neurological diseases can be successfully treated with natural substances. As a result, current research has been concentrated on finding effective neuroprotective drugs with improved efficacy and fewer side effects. Naringenin is one potential treatment for neurodegenerative diseases. Many citrus fruits, tomatoes, bergamots, and other fruits are rich in naringenin, a flavonoid. This phytochemical is linked to a variety of biological functions. Naringenin has attracted a lot of interest for its ability to exhibit neuroprotection through several mechanisms. In the current article, we present evidence from the literature that naringenin reduces neurotoxicity and oxidative stress in brain tissues. Also, the literatures that are currently accessible shows that naringenin reduces neuroinflammation and other neurological anomalies. Additionally, we found several studies that touted naringenin as a promising anti-amyloidogenic, antidepressant, and neurotrophic treatment option. This review's major goal is to reflect on advancements in knowledge of the molecular processes that underlie naringenin's possible neuroprotective effects. Furthermore, this article also provides highlights of Naringenin with respect to its chemistry and pharmacokinetics.

Electroacupuncture Improves Neuronal Damage and Mitochondrial Dysfunction Through the TRPC1 and SIRT1/AMPK Signaling Pathways to Alleviate Parkinson's Disease in Mice

Parkinson's disease (PD) is a neurodegenerative disease that mainly manifests as cognitive decline and motor dysfunction, the treatment of which is still a major challenge in the clinical field. Acupuncture therapy has been shown in many studies to enhance the body's own immunity and disease resistance. This study mainly discusses the specific mechanism underlying electroacupuncture intervention in improving PD. Male C57BL/6 mice were intraperitoneally injected with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to induce a mouse PD model, and the chorea trembling control area of the head of PD mice was treated by electroacupuncture. Western blotting was used to detect the expression of related proteins in mouse pathological samples; TUNEL measured neuronal apoptosis levels; Nissl staining observed neuronal damage; immunofluorescence and immunohistochemistry were used to detect the expression of Iba-1, TH, and α-syn in substantia nigra denser (SN). The expression levels of oxidative stress factors and inflammatory factors were measured by kits. Flow cytometry measured mitochondrial membrane potential and Ca2+ levels. MPTP intraperitoneal injection induced an increase in inflammatory factors in PD mice and promoted the oxidative stress response, and the inflammatory response was alleviated after electroacupuncture treatment. Electroacupuncture intervention effectively alters the decrease in oxidative stress levels and alleviates neuronal damage in PD mice. Electroacupuncture improves mitochondrial dysfunction induced by MPTP in PD mice by activating the SIRT1/AMPK signaling pathway. We also confirmed that knocking down TRPC1 can inhibit the SIRT1/AMPK signaling pathway, weaken the Ca2+ content in mouse neuronal tissue, and promote cell apoptosis. Electroacupuncture improves neuronal damage and alleviates PD in mice through the TRPC1 and SIRT1/AMPK signaling pathways. In addition, electroacupuncture therapy can improve MPTP-induced mitochondrial dysfunction in PD mice and alleviate the PD process.

Cracking the Endothelial Calcium (Ca2+) Code: A Matter of Timing and Spacing

A monolayer of endothelial cells lines the innermost surface of all blood vessels, thereby coming into close contact with every region of the body and perceiving signals deriving from both the bloodstream and parenchymal tissues. An increase in intracellular Ca2+ concentration ([Ca2+]i) is the main mechanism whereby vascular endothelial cells integrate the information conveyed by local and circulating cues. Herein, we describe the dynamics and spatial distribution of endothelial Ca2+ signals to understand how an array of spatially restricted (at both the subcellular and cellular levels) Ca2+ signals is exploited by the vascular intima to fulfill this complex task. We then illustrate how local endothelial Ca2+ signals affect the most appropriate vascular function and are integrated to transmit this information to more distant sites to maintain cardiovascular homeostasis. Vasorelaxation and sprouting angiogenesis were selected as an example of functions that are finely tuned by the variable spatio-temporal profile endothelial Ca2+ signals. We further highlighted how distinct Ca2+ signatures regulate the different phases of vasculogenesis, i.e., proliferation and migration, in circulating endothelial precursors.

TRP (transient receptor potential) ion channel family: structures, biological functions and therapeutic interventions for diseases

Transient receptor potential (TRP) channels are sensors for a variety of cellular and environmental signals. Mammals express a total of 28 different TRP channel proteins, which can be divided into seven subfamilies based on amino acid sequence homology: TRPA (Ankyrin), TRPC (Canonical), TRPM (Melastatin), TRPML (Mucolipin), TRPN (NO-mechano-potential, NOMP), TRPP (Polycystin), TRPV (Vanilloid). They are a class of ion channels found in numerous tissues and cell types and are permeable to a wide range of cations such as Ca²⁺, Mg²⁺, Na⁺, K⁺, and others. TRP channels are responsible for various sensory responses including heat, cold, pain, stress, vision and taste and can be activated by a number of stimuli. Their predominantly location on the cell surface, their interaction with numerous physiological signaling pathways, and the unique crystal structure of TRP channels make TRPs attractive drug targets and implicate them in the treatment of a wide range of diseases. Here, we review the history of TRP channel discovery, summarize the structures and functions of the TRP ion channel family, and highlight the current understanding of the role of TRP channels in the pathogenesis of human disease. Most importantly, we describe TRP channel-related drug discovery, therapeutic interventions for diseases and the limitations of targeting TRP channels in potential clinical applications.

TRPV4 channel is involved in HSV-2 infection in human vaginal epithelial cells through triggering Ca2+ oscillation

Herpes simplex virus (HSV) infection induces a rapid and transient increase in intracellular calcium concentration ([Ca2+]i), which plays a critical role in facilitating viral entry. T-type calcium channel blockers and EGTA, a chelate of extracellular Ca2+, suppress HSV-2 infection. But the cellular mechanisms mediating HSV infection-activated Ca2+ signaling have not been completely defined. In this study we investigated whether the TRPV4 channel was involved in HSV-2 infection in human vaginal epithelial cells. We showed that the TRPV4 channel was expressed in human vaginal epithelial cells (VK2/E6E7). Using distinct pharmacological tools, we demonstrated that activation of the TRPV4 channel induced Ca2+ influx, and the TRPV4 channel worked as a Ca2+-permeable channel in VK2/E6E7 cells. We detected a direct interaction between the TRPV4 channel protein and HSV-2 glycoprotein D in the plasma membrane of VK2/E6E7 cells and the vaginal tissues of HSV-2-infected mice as well as in phallic biopsies from genital herpes patients. Pretreatment with specific TRPV4 channel inhibitors, GSK2193874 (1-4 μM) and HC067047 (100 nM), or gene silence of the TRPV4 channel not only suppressed HSV-2 infectivity but also reduced HSV-2-induced cytokine and chemokine generation in VK2/E6E7 cells by blocking Ca2+ influx through TRPV4 channel. These results reveal that the TRPV4 channel works as a Ca2+-permeable channel to facilitate HSV-2 infection in host epithelial cells and suggest that the design and development of novel TRPV4 channel inhibitors may help to treat HSV-2 infections.

The Molecular Heterogeneity of Store-Operated Ca2+ Entry in Vascular Endothelial Cells: The Different roles of Orai1 and TRPC1/TRPC4 Channels in the Transition from Ca2+-Selective to Non-Selective Cation Currents

Store-operated Ca²⁺ entry (SOCE) is activated in response to the inositol-1,4,5-trisphosphate (InsP₃)-dependent depletion of the endoplasmic reticulum (ER) Ca²⁺ store and represents a ubiquitous mode of Ca²⁺ influx. In vascular endothelial cells, SOCE regulates a plethora of functions that maintain cardiovascular homeostasis, such as angiogenesis, vascular tone, vascular permeability, platelet aggregation, and monocyte adhesion. The molecular mechanisms responsible for SOCE activation in vascular endothelial cells have engendered a long-lasting controversy. Traditionally, it has been assumed that the endothelial SOCE is mediated by two distinct ion channel signalplexes, i.e., STIM1/Orai1 and STIM1/Transient Receptor Potential Canonical 1(TRPC1)/TRPC4. However, recent evidence has shown that Orai1 can assemble with TRPC1 and TRPC4 to form a non-selective cation channel with intermediate electrophysiological features. Herein, we aim at bringing order to the distinct mechanisms that mediate endothelial SOCE in the vascular tree from multiple species (e.g., human, mouse, rat, and bovine). We propose that three distinct currents can mediate SOCE in vascular endothelial cells: (1) the Ca²⁺-selective Ca²⁺-release activated Ca²⁺ current (I_CRAC), which is mediated by STIM1 and Orai1; (2) the store-operated non-selective current (I_SOC), which is mediated by STIM1, TRPC1, and TRPC4; and (3) the moderately Ca²⁺-selective, I_CRAC-like current, which is mediated by STIM1, TRPC1, TRPC4, and Orai1.

Arbitrary Ca2+ regulation for endothelial nitric oxide, NFAT and NF-κB activities by an optogenetic approach

Modern western dietary habits and low physical activity cause metabolic abnormalities and abnormally elevated levels of metabolites such as low-density lipoprotein, which can lead to immune cell activation, and inflammatory reactions, and atherosclerosis. Appropriate stimulation of vascular endothelial cells can confer protective responses against inflammatory reactions and atherosclerotic conditions. This study aims to determine whether a designed optogenetic approach is capable of affecting functional changes in vascular endothelial cells and to evaluate its potential for therapeutic regulation of vascular inflammatory responses in vitro. We employed a genetically engineered, blue light-activated Ca²⁺ channel switch molecule that utilizes an endogenous store-operated calcium entry system and induces intracellular Ca²⁺ influx through blue light irradiation and observed an increase in intracellular Ca²⁺ in vascular endothelial cells. Ca²⁺-dependent activation of the nuclear factor of activated T cells and nitric oxide production were also detected. Microarray analysis of Ca²⁺-induced changes in vascular endothelial cells explored several genes involved in cellular contractility and inflammatory responses. Indeed, there was an increase in the gene expression of molecules related to anti-inflammatory and vasorelaxant effects. Thus, a combination of human blue light-activated Ca²⁺ channel switch 2 (hBACCS2) and blue light possibly attenuates TNFα-induced inflammatory NF-κB activity. We propose that extrinsic cellular Ca²⁺ regulation could be a novel approach against vascular inflammation.

Macrophage P2Y6 Receptor Signaling Selectively Activates NFATC2 and Suppresses Allergic Lung Inflammation

Innate immune responses to innocuous Ags can either prevent or facilitate adaptive type 2 allergic inflammation, but the mechanisms are incompletely understood. We now demonstrate that macrophage UDP-specific type 6 purinergic (P2Y6) receptors selectively activate NFATC2, a member of the NFAT family, to drive an innate IL-12/IFN-γ axis that prevents type 2 allergic inflammation. UDP priming potentiated IL-12p40 production in bone marrow-derived macrophages (BMMs) stimulated by the house dust mite Dermatophagoides farinae (Df) in a P2Y6-dependent manner. Inhibitions of phospholipase C, calcium increase, and calcineurin eliminated UDP-potentiated Df-induced IL-12p40 production. UDP specifically induced nuclear translocation of NFATC2, but not NFATC1 and NFATC3, in BMMs in a P2Y6-dependent manner. UDP-potentiated IL-12p40 production by BMMs and Df-induced IL-12p40 gene expression by alveolar macrophages were abrogated in cells from Nfatc2 knockout mice. Pulmonary transplantation of wild-type but not Nfatc2 knockout macrophages increased Df-induced IL-12 production and IFN-γ expression in P2ry6 fl/fl/Cre/+ recipient mice. Finally, Nfatc2 knockout mice showed significantly increased indices of type 2 immunopathology in response to Df challenge, similar to P2ry6 fl/fl/Cre/+ mice. Thus, macrophage P2Y6 receptor signaling selectively utilizes NFATC2 to potentiate an innate IL-12/IFN-γ axis, a potential mechanism that protects against inappropriate type 2 immune responses.

Therapeutic Targeting of NF-κB in Acute Lung Injury: A Double-Edged Sword

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a devastating disease that can be caused by a variety of conditions including pneumonia, sepsis, trauma, and most recently, COVID-19. Although our understanding of the mechanisms of ALI/ARDS pathogenesis and resolution has considerably increased in recent years, the mortality rate remains unacceptably high (~40%), primarily due to the lack of effective therapies for ALI/ARDS. Dysregulated inflammation, as characterized by massive infiltration of polymorphonuclear leukocytes (PMNs) into the airspace and the associated damage of the capillary-alveolar barrier leading to pulmonary edema and hypoxemia, is a major hallmark of ALI/ARDS. Endothelial cells (ECs), the inner lining of blood vessels, are important cellular orchestrators of PMN infiltration in the lung. Nuclear factor-kappa B (NF-κB) plays an essential role in rendering the endothelium permissive for PMN adhesion and transmigration to reach the inflammatory site. Thus, targeting NF-κB in the endothelium provides an attractive approach to mitigate PMN-mediated vascular injury, not only in ALI/ARDS, but in other inflammatory diseases as well in which EC dysfunction is a major pathogenic mechanism. This review discusses the role and regulation of NF-κB in the context of EC inflammation and evaluates the potential and problems of targeting it as a therapy for ALI/ARDS.

Deciphering the Role of the Coagulation Cascade and Autophagy in Cancer-Related Thrombosis and Metastasis

Thrombotic complications are the second leading cause of death among oncology patients worldwide. Enhanced thrombogenesis has multiple origins and may result from a deregulation of megakaryocyte platelet production in the bone marrow, the synthesis of coagulation factors in the liver, and coagulation factor signaling upon cancer and the tumor microenvironment (TME). While a hypercoagulable state has been attributed to factors such as thrombocytosis, enhanced platelet aggregation and Tissue Factor (TF) expression on cancer cells, further reports have suggested that coagulation factors can enhance metastasis through increased endothelial-cancer cell adhesion and enhanced endothelial cell activation. Autophagy is highly associated with cancer survival as a double-edged sword, as can both inhibit and promote cancer progression. In this review, we shall dissect the crosstalk between the coagulation cascade and autophagic pathway and its possible role in metastasis and cancer-associated thrombosis formation. The signaling of the coagulation cascade through the autophagic pathway within the hematopoietic stem cells, the endothelial cell and the cancer cell are discussed. Relevant to the coagulation cascade, we also examine the role of autophagy-related pathways in cancer treatment. In this review, we aim to bring to light possible new areas of cancer investigation and elucidate strategies for future therapeutic intervention.

Cryptotanshinone-Induced p53-Dependent Sensitization of Colon Cancer Cells to Apoptotic Drive by Regulation of Calpain and Calcium Homeostasis

Over-expression of calpains in tumor tissues can be associated with cancer progression. Thus, inhibition of calpain activity using specific inhibitors has become a novel approach to control tumor growth. In this study, the anticancer potential of cryptotanshinone in combination with calpain inhibitor had been investigated in colon cancer cells and tumor xenograft. Cryptotanshinone elicited an initial endoplasmic reticular (ER) stress response, whereas prolonged stress would result in the promotion of apoptosis. It was then discovered that cryptotanshinone could cause rapid and sustained increase in cytosolic calcium in colon cancer cells accompanied by early GRP78 overexpression, which could be attenuated by pre-treatment of the calcium chelator BAPTA-AM. Cryptotanshinone also facilitated an early increase in calpain activity, which could be blocked by BAPTA-AM or the calpain inhibitor PD150606. A dynamic interaction between GRP78 and calpain during the action of cryptotanshinone was unveiled. This together with the altered NF-[Formula: see text]B signaling could be abolished by calpain inhibitor. GRP78 knockdown increased the sensitivity of cancer cells to cryptotanshinone-evoked apoptosis and reduction of cancer cell colony formation. Such sensitization of drug action had been confirmed to be p53-dependent by using p53-mutated (HT-29) and p53-deficient (HCT116 p53^-∕-) cells. The synergistic antitumor effect of cryptotanshinone and calpain inhibitor was further exhibited in vivo. Taken together, findings in this study exemplify a new chemotherapeutic regimen comprising cryptotanshinone and calpain inhibitor by regulation of calpain and calcium homeostasis. This has provided us with new insights in the search of a potential target-specific neoadjuvant therapy against colon cancer.

CaMK4-dependent phosphorylation of Akt/mTOR underlies Th17 excessive activation in experimental autoimmune prostatitis

Chronic prostatitis and chronic pelvic pain syndrome (CP/CPPS) is a complicated syndrome characterized by genitourinary pain in the absence of bacterial infection. Th17 cell-driven autoimmunity has been proposed as a cause of CP/CPPS. However, the factors that promote Th17-driven autoimmunity in experimental autoimmune prostatitis (EAP) and the molecular mechanisms are still largely unknown. Here, we showed that Th17 cells were excessively activated, and blockade of IL-17A could effectively ameliorate various symptoms in EAP. Furthermore, we revealed that calcium/calmodulin-dependent kinase Ⅳ (CaMK4), especially Thr196 p-CaMK4 was increased in the Th17 cells of the EAP group, which were activated by intracellular cytosolic Ca2+ . Pharmacologic and genetic inhibition of CaMK4 decreased the proportion of Th17 cells, and the protein and mRNA level of IL-17A, IL-22, and RORγt. The phosphorylation of CaMK4 was dependent on the increase in intracellular cytosolic Ca2+ concentration in Th17 cells. A mechanistic study demonstrated that inhibition of CaMK4 reduced IL-17A production by decreasing the phosphorylation of Akt-mTOR, which was well accepted to positively regulate Th17 differentiation. Collectively, our results demonstrated that Ca2+ -CaMK4-Akt/mTOR-IL-17A axis inhibition may serve as a promising therapeutic strategy for CP/CPPS.

Macrophage TLR4 and PAR2 Signaling: Role in Regulating Vascular Inflammatory Injury and Repair

Macrophages play a central role in dictating the tissue response to infection and orchestrating subsequent repair of the damage. In this context, macrophages residing in the lungs continuously sense and discriminate among a wide range of insults to initiate the immune responses important to host-defense. Inflammatory tissue injury also leads to activation of proteases, and thereby the coagulation pathway, to optimize injury and repair post-infection. However, long-lasting inflammatory triggers from macrophages can impair the lung's ability to recover from severe injury, leading to increased lung vascular permeability and neutrophilic injury, hallmarks of Acute Lung Injury (ALI). In this review, we discuss the roles of toll-like receptor 4 (TLR4) and protease activating receptor 2 (PAR2) expressed on the macrophage cell-surface in regulating lung vascular inflammatory signaling.

Chromogranin A (CGA)-derived polypeptide (CGA47-66) inhibits TNF-α-induced vascular endothelial hyper-permeability through SOC-related Ca2+ signaling

CGA_1-78 (Vasostatin-1, VS-1) a N-terminal Chromogranin A (CGA)-derived peptide, has been shown to have a protective effect against TNF-α-induced impairment of endothelial cell integrity. However, the mechanisms of this effect have not yet been clarified. CGA_47-66 (Chromofungin, CHR) is an important bioactive fragment of CGA_1-78. The present study aims to explore the protective effects of CHR on the vascular endothelial cell barrier response to TNF-α and its related Ca²⁺ signaling mechanisms. EA.hy926 cells were used as a vascular endothelial culture model. The synthetic peptides CHR and CGA_4-16 were assessed for their ability to suppress TNF-α-induced EA.hy926 cells hyper-permeability through Transwell® and TEER assays. Changes in [Ca²⁺]_i were measured through confocal laser scanning microscopy. SOC channel currents (Isoc) were measured via patch-clamp analysis. RT-PCR and western blot were used to analyze mRNA and protein expression of the transient receptor potential channels TRPC1 and TRPC4, respectively. FITC and rhodamine-phalloidin fluorescence were used to assess cell morphology and the distribution of MyPT-1 and F-actin. Compared to untreated cells, TNF-α increased the permeability of EA.hy926 cells that was inhibited by pre-treatment with CHR (10-1000 nM) in concentration-dependent manner, and the effect was most obvious at 100 nM, but CGA_4-16 (100 nM) had no effect. TNF-α treatment increased the phosphorylation of MyPT-1 and stress fiber formation. CHR (10-1000 nM) pretreatment inhibited the cytoskeletal rearrangements and increased [Ca²⁺]_i in response to TNF-α treatment. CHR also reduced TRPC1 expression following TNF-α induction. Similar to SOC inhibitor 2-APB, CHR suppressed IP₃ mediated SOC activation. These findings suggest that CHR inhibits TNF-α-induced Ca²⁺ influx and protects the barrier function of vascular endothelial cells, and that these effects are related to the inhibition of SOC and Ca²⁺ signaling by CHR.

PAR2-Mediated cAMP Generation Suppresses TRPV4-Dependent Ca2+ Signaling in Alveolar Macrophages to Resolve TLR4-Induced Inflammation

Alveolar macrophages (AMs), upon sensing pathogens, trigger host defense by activating toll-like receptor 4 (TLR4), but the counterbalancing mechanisms that deactivate AM inflammatory signaling and prevent lethal edema, the hallmark of acute lung injury (ALI), remain unknown. Here, we demonstrate the essential role of AM protease-activating receptor 2 (PAR2) in rapidly suppressing inflammation to prevent long-lasting injury. We show that thrombin, released during TLR4-induced lung injury, directly activates PAR2 to generate cAMP, which abolishes Ca²⁺ entry through the TRPV4 channel. Deletion of PAR2 and thus the accompanying cAMP generation augments Ca²⁺ entry via TRPV4, causing sustained activation of the transcription factor NFAT to produce long-lasting TLR4-mediated inflammatory lung injury. Rescuing thrombin-sensitive PAR2 expression or blocking TRPV4 activity in PAR2-null AMs restores their capacity to resolve inflammation and reverse lung injury. Thus, activation of the thrombin-induced PAR2-cAMP cascade in AMs suppresses TLR4 inflammatory signaling to reinstate tissue integrity.

On the Neuroprotective Effects of Naringenin: Pharmacological Targets, Signaling Pathways, Molecular Mechanisms, and Clinical Perspective

As a group of progressive, chronic, and disabling disorders, neurodegenerative diseases (NDs) affect millions of people worldwide, and are on the rise. NDs are known as the gradual loss of neurons; however, their pathophysiological mechanisms have not been precisely revealed. Due to the complex pathophysiological mechanisms behind the neurodegeneration, investigating effective and multi-target treatments has remained a clinical challenge. Besides, appropriate neuroprotective agents are still lacking, which raises the need for new therapeutic agents. In recent years, several reports have introduced naturally-derived compounds as promising alternative treatments for NDs. Among natural entities, flavonoids are multi-target alternatives affecting different pathogenesis mechanisms in neurodegeneration. Naringenin is a natural flavonoid possessing neuroprotective activities. Increasing evidence has attained special attention on the variety of therapeutic targets along with complex signaling pathways for naringenin, which suggest its possible therapeutic applications in several NDs. Here, in this review, the neuroprotective effects of naringenin, as well as its related pharmacological targets, signaling pathways, molecular mechanisms, and clinical perspective, are described. Moreover, the need to develop novel naringenin delivery systems is also discussed to solve its widespread pharmacokinetic limitation.

Passing the Vascular Barrier: Endothelial Signaling Processes Controlling Extravasation

A central function of the vascular endothelium is to serve as a barrier between the blood and the surrounding tissue of the body. At the same time, solutes and cells have to pass the endothelium to leave or to enter the bloodstream to maintain homeostasis. Under pathological conditions, for example, inflammation, permeability for fluid and cells is largely increased in the affected area, thereby facilitating host defense. To appropriately function as a regulated permeability filter, the endothelium uses various mechanisms to allow solutes and cells to pass the endothelial layer. These include transcellular and paracellular pathways of which the latter requires remodeling of intercellular junctions for its regulation. This review provides an overview on endothelial barrier regulation and focuses on the endothelial signaling mechanisms controlling the opening and closing of paracellular pathways for solutes and cells such as leukocytes and metastasizing tumor cells.

Anti-GRP78 autoantibodies induce endothelial cell activation and accelerate the development of atherosclerotic lesions

The 78-kDa glucose-regulated protein (GRP78) is an ER molecular chaperone that aids in protein folding and secretion. However, pathological conditions that cause ER stress can promote the relocalization of GRP78 to the cell surface (csGRP78), where it acts as a signaling receptor to promote cancer progression. csGRP78 also possesses antigenic properties, leading to the production of anti-GRP78 autoantibodies, which contribute to tumor growth. In contrast, the presence and role of anti-GRP78 autoantibodies in atherosclerosis is unknown. Here, we show that atherosclerotic-prone ApoE-/- mice develop circulating anti-GRP78 autoantibodies that bind to csGRP78 on lesion-resident endothelial cells. Moreover, GRP78-immunized ApoE-/- mice exhibit a marked increase in circulating anti-GRP78 autoantibody titers that correlated with accelerated lesion growth. Mechanistically, engagement of anti-GRP78 autoantibodies with csGRP78 on human endothelial cells activated NF-κB, thereby inducing the expression of ICAM-1 and VCAM-1, a process blocked by NF-κB inhibitors. Disrupting the autoantibody/csGRP78 complex with enoxaparin, a low-molecular-weight heparin, reduced the expression of adhesion molecules and attenuated lesion growth. In conclusion, anti-GRP78 autoantibodies play a crucial role in atherosclerosis development, and disruption of the interaction between anti-GRP78 autoantibodies and csGRP78 represents a therapeutic strategy.

BP-1T, an antiangiogenic benzophenone-thiazole pharmacophore, counteracts HIF-1 signalling through p53/MDM2-mediated HIF-1α proteasomal degradation

Hypoxia is a feature of all solid tumours, contributing to tumour progression. Activation of HIF-1α plays a critical role in promoting tumour angiogenesis and metastasis. Since its expression is positively correlated with poor prognosis for cancer patients, HIF-1α is one of the most convincing anticancer targets. BP-1T is a novel antiproliferative agent with promising antiangiogenic effects. In the present study, the molecular mechanism underlying cytotoxic/antiangiogenic effects of BP-1T on tumour/non-tumour angiogenesis was evaluated. Evidences show that BP-1T exhibits potent cytotoxicity with prolonged activity and effectively regressed neovessel formation both in reliable non-tumour and tumour angiogenic models. The expression of CoCl₂-induced HIF-1α was inhibited by BP-1T in various p53 (WT)-expressing cancer cells, including A549, MCF-7 and DLA, but not in mutant p53-expressing SCC-9 cells. Mechanistically, BP-1T mediates the HIF-1α proteasomal degradation by activating p53/MDM2 pathway and thereby downregulated HIF-1α-dependent angiogenic genes such as VEGF-A, Flt-1, MMP-2 and MMP-9 under hypoxic condition of in vitro and in vivo solid tumour, eventually leading to abolition of migration and invasion. Based on these observations, we conclude that BP-1T acts on HIF-1α degradation through p53/MDM2 proteasome pathway.

Mitochondrial uncoupler carbonyl cyanide m-chlorophenylhydrazone induces vasorelaxation without involving KATP channel activation in smooth muscle cells of arteries

BACKGROUND AND PURPOSE

The effects and mechanisms of chemical mitochondrial uncouplers on vascular function have never been identified. Here, we characterized the effects of the typical mitochondrial uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) on vascular function in rat mesenteric arteries and aorta and elucidated the potential mechanisms.

EXPERIMENTAL APPROACH

Isometric tension of mesenteric artery and thoracic aorta was recorded by using a multiwire myograph system. Protein levels were measured by western blot analyses. Cytosolic [Ca²⁺ ]_i , mitochondrial ROS (mitoROS) and mitochondrial membrane potential of smooth muscle cells (A10) were measured by laser scanning confocal microscopy.

KEY RESULTS

Acute treatment with CCCP relaxed phenylephrine (PE)- and high K⁺ (KPSS)-induced constriction of rat mesenteric arteries with intact and denuded endothelium. Pretreatment with CCCP prevented PE- and KPSS-induced constriction of rat mesenteric arteries with intact and denuded endothelium. Similarly, CCCP prevented PE- and KPSS-induced constriction of rat thoracic aorta. CCCP increased the cellular ADP/ATP ratio in vascular smooth muscle cells (A10) and activated AMPK in A10 cells and rat thoracic aorta tissues. CCCP-induced aorta relaxation was attenuated in AMPK α1 knockout (-/-) mice. SERCA inhibitors thapsigargin and cyclopiazonic acid (CPA) but not the K_ATP channel blocker glibenclamide partially inhibited CCCP-induced vasorelaxation in endothelium-denuded rat mesenteric arteries. CCCP increased cytosolic [Ca²⁺ ]_i , mitoROS production and depolarized mitochondrial membrane potential in A10 cells. FCCP, the analogue of CCCP, had similar vasoactivity as CCCP in rat mesenteric arteries.

CONCLUSIONS AND IMPLICATIONS

CCCP induces vasorelaxation by a mechanism that does not involve K_ATP channel activation in smooth muscle cells of arteries.

Transient Receptor Potential Vanilloid 4 Inhibits γ-Aminobutyric Acid-Activated Current in Hippocampal Pyramidal Neurons

The balance between excitatory and inhibitory neurotransmitter systems is crucial for the modulation of neuronal excitability in the central nervous system (CNS). The activation of transient receptor potential vanilloid 4 (TRPV4) is reported to enhance the response of hippocampal glutamate receptors, but whether the inhibitory neurotransmitter system can be regulated by TRPV4 remains unknown. γ-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the CNS. Here, we show that application of transient receptor potential vanilloid 4 (TRPV4) synthetic (GSK1016790A or 4α-PDD) or endogenous agonist (5,6-EET) inhibited GABA-activated current (I_GABA) in hippocampal CA1 pyramidal neurons, which was blocked by specific antagonists of TRPV4 and of GABA_A receptors. GSK1016790A increased the phosphorylated AMP-activated protein kinase (p-AMPK) and decreased the phosphorylated protein kinase B (p-Akt) protein levels, which was attenuated by removing extracellular calcium or by a calcium/calmodulin-dependent protein kinase kinase-β antagonist. GSK1016790A-induced decrease of p-Akt protein level was sensitive to an AMPK antagonist. GSK1016790A-inhibited I_GABA was blocked by an AMPK antagonist or a phosphatidyl inositol 3 kinase (PI3K) agonist. GSK1016790A-induced inhibition of I_GABA was also significantly attenuated by a protein kinase C (PKC) antagonist but was unaffected by protein kinase A or calcium/calmodulin-dependent protein kinase II antagonist. We conclude that activation of TRPV4 inhibits GABA_A receptor, which may be mediated by activation of AMPK and subsequent down-regulation of PI3K/Akt signaling and activation of PKC signaling. Inhibition of GABA_A receptors may account for the neuronal hyperexcitability caused by TRPV4 activation.

Gene expression profiling of DMU-212-induced apoptosis and anti-angiogenesis in vascular endothelial cells

CONTEXT

trans-3,4,5,4'-Tetramethoxystilbene (DMU-212), an derivative of resveratrol, shows strong antiproliferative activities against many cancer cells. In our previous study, we demonstrated that DMU-212 possesses potent proapoptosis and antiangiogenesis effects on vascular endothelial cells (VECs), which made it a promising agent for the treatment of angiogenesis-related diseases.

OBJECTIVE

We studied the gene expression profile of DMU-212-treated VECs to gain further insight into the mechanisms by which DMU-212 exerts its potent pro-apoptosis and antiangiogenesis effects.

MATERIALS AND METHODS

The potential changes in the gene expression of VECs incubated with DMU-212 were identified and analyzed using the Affymetrix HG-U133 Plus 1.0 array. In addition, the gene expression profile was validated by quantitative real-time PCR (qRT-PCR) analysis for seven of those altered genes.

RESULTS AND CONCLUSION

DMU-212 was found to regulate a diverse range of genes, including cytokines (IL8, selectin E, MPZL2, EGR1, CCL20, ITGB8, CXCL1, VCAM1, KITLG, and AREG), transport proteins (TRPC4, SLC41A2, SLC17A5, and CREB5), metabolism (CYP1B1, CYP1A1, PDK4, CSNK1G1, MVK, TCEB3C, and CDKN3), enzymes (RAB23, SPHK1, CHSY3, PLAU, PLA2G4C, and MMP10), and genes involved in signal transduction (TMEM217, DUSP8, and SPRY4), chromosome organization (HIST1H2BH and GEM), cell migration and angiogenesis (ERRFI1, HBEGF, and NEDD9), and apoptosis (TNFSF15, TNFRSF9, CD274, BCL2L11, BIRC3, TNFAIP3, and TIFA), as well as other genes with unknown function (PGM5P2, SNORD1142, LOC151760, KRTAP5-2, C1orf110, SNORA14A, MIR31, C2CD4B, SCARNA4, C2orf66, SC4MOL, LOC644714, and LOC283392). This is the first application of microarray technique to investigate and analyze the profile of genes regulated by DMU-212 in VECs. Our results lead to an increased understanding of the signaling pathways involved in DMU-212-induced apoptosis and antiangiogenesis.

Canonical transient receptor potential 3 channels activate NF-κB to mediate allergic airway disease via PKC-α/IκB-α and calcineurin/IκB-β pathways

The purpose of this study was to determine the role of canonical transient receptor potential 3 (TRPC3) channel in allergen-induced airway disease (AIAD) and its underlying signaling mechanisms. The procedures included (1) intravenous injection of lentiviral TRPC3 channel or nonsilencing short hairpin ribonucleic acid (shRNA) to make the channel knockdown (KD) or control mice, (2) allergen sensitization/challenge to induce AIAD, (3) patch-clamp recording and Ca(2+) imaging to examine the channel activity, and (4) gene manipulations and other methods to determine the underlying signaling mechanisms. The findings are that (1) intravenous or intranasal delivery of TRPC3 channel lentiviral shRNAs or blocker 1-[4-[(2,3,3-trichloro-1-oxo-2-propen-1-yl)amino]phenyl]-5-(trifluoromethyl)-1H-pyrazole-4-carboxylic acid prevents AIAD in mice, (2) TRPC3 channel KD and overexpression, respectively, blocks and augments protein kinase C-α/nuclear factor of κ light polypeptide gene enhancer in B-cell inhibitor-α (PKC-α/IκB-α)-mediated or calcineurin/IκB-β-dependent, NF-κB-dependent allergen-induced airway smooth muscle cell (ASMC) hyperproliferation and cyclin D1 (an important cell proliferation molecule) induction, and (3) the changes of the major molecules of the PKC-α/IκBα- and calcineurin/IκB-β-dependent NF-κB signaling pathways are also observed in asthmatic human ASMCs. The conclusions are that TRPC3 channels plays an essential role in AIAD via the PKC-α/IκB-α- and calcineurin/IκB-β-dependent NF-κB signaling pathways, and lentiviral shRNA or inhibitor of TRPC3 channels may become novel and effective treatments for AIAD.

Impact of AMP-Activated Protein Kinase α1 Deficiency on Tissue Injury following Unilateral Ureteral Obstruction

Background

AMP-activated protein kinase (Ampk) is a sensor of the cellular energy status and a powerful regulator of metabolism. Activation of Ampk was previously shown to participate in monocyte-to-fibroblast transition and matrix protein production in renal tissue. Thus, the present study explored whether the catalytic Ampkα1 isoform participates in the regulation of the renal fibrotic response following unilateral ureteral obstruction (UUO).

Methods

UUO was induced in gene-targeted mice lacking functional Ampkα1 (Ampkα1^-/-) and in corresponding wild-type mice (Ampkα1^+/+). In the obstructed kidney and, for comparison, in the non-obstructed control kidney, quantitative RT-PCR, Western blotting and immunostaining were employed to determine transcript levels and protein abundance, respectively.

Results

In Ampkα1^+/+ mice, UUO significantly up-regulated the protein abundance of the Ampkα1 isoform, but significantly down-regulated the Ampkα2 isoform in renal tissue. Phosphorylated Ampkα protein levels were significantly increased in obstructed kidney tissue of Ampkα1^+/+ mice but not of Ampkα1^-/- mice. Renal expression of α-smooth muscle actin was increased following UUO, an effect again less pronounced in Ampkα1^-/- mice than in Ampkα1^+/+ mice. Histological analysis did not reveal a profound effect of Ampkα1 deficiency on collagen 1 protein deposition. UUO significantly increased phosphorylated and total Tgf-ß-activated kinase 1 (Tak1) protein, as well as transcript levels of Tak1-downstream targets c-Fos, Il6, Pai1 and Snai1 in Ampkα1^+/+ mice, effects again significantly ameliorated in Ampkα1^-/- mice. Moreover, Ampkα1 deficiency inhibited the UUO-induced mRNA expression of Cd206, a marker of M2 macrophages and of Cxcl16, a pro-fibrotic chemokine associated with myeloid fibroblast formation. The effects of Ampkα1 deficiency during UUO were, however, paralleled by increased tubular injury and apoptosis.

Conclusions

Renal obstruction induces an isoform shift from Ampkα2 towards Ampkα1, which contributes to the signaling involved in cell survival and fibrosis.

Regulatory effects of caffeic acid phenethyl ester on neuroinflammation in microglial cells

Microglial activation has been widely demonstrated to mediate inflammatory processes that are crucial in several neurodegenerative disorders. Pharmaceuticals that can deliver direct inhibitory effects on microglia are therefore considered as a potential strategy to counter balance neurodegenerative progression. Caffeic acid phenethyl ester (CAPE), a natural phenol in honeybee propolis, is known to possess antioxidant, anti-inflammatory and anti-microbial properties. Accordingly, the current study intended to probe the effects of CAPE on microglia activation by using in vitro and in vivo models. Western blot and Griess reaction assay revealed CAPE significantly inhibited the expressions of inducible nitric oxide synthase (NOS), cyclooxygenase (COX)-2 and the production of nitric oxide (NO). Administration of CAPE resulted in increased expressions of hemeoxygenase (HO)-1and erythropoietin (EPO) in microglia. The phosphorylated adenosine monophosphate-activated protein kinase (AMPK)-α was further found to regulate the anti-inflammatory effects of caffeic acid. In vivo results from immunohistochemistry along with rotarod test also revealed the anti-neuroinflammatory effects of CAPE in microglia activation. The current study has evidenced several possible molecular determinants, AMPKα, EPO, and HO-1, in mediating anti-neuroinflammatory responses in microglial cells.

Naringenin Suppresses Neuroinflammatory Responses Through Inducing Suppressor of Cytokine Signaling 3 Expression

Accumulating evidence suggests that neuroinflammation is closely associated with the pathogenesis of neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. The hallmark of neuroinflammation is considered to be microglial activation in the central nervous system (CNS). Activated microglia release pro-inflammatory cytokines which cause neuroinflammation and progressive neuronal cell death. Therefore, inhibition of microglial activation is considered an important strategy in the development of neuroprotective strategy. Naringenin, a flavonoid found in citrus fruits and tomatoes, has been reported to have anti-oxidant, anti-cancer, and anti-inflammatory properties. However, the mechanism of its beneficial anti-inflammatory effects in the CNS is poorly understood. In this study, we demonstrated that naringenin inhibites the release of nitric oxide (NO), the expression of inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2), as well as pro-inflammatory cytokines in microglial cells. Treatment of naringenin also induced suppressors of cytokine signaling (SOCS)-3 expression in microglia. The SOCS-3 expression and anti-inflammatory effects of naringenin were found to be regulated by adenosine monophosphate-activated protein kinase α (AMPKα) and protein kinase C δ (PKCδ). Besides, naringenin exerted protective property against neurotoxicity caused by LPS-induced microglial activation. Our findings suggest that naringenin-inhibited iNOS and COX-2 expression is mediated by SOCS-3 activation through AMPKα and PKCδ signaling pathways. In a mouse model, naringenin also showed significant protective effects on microglial activation and improved motor coordination function as well. Therefore, naringenin that involves in anti-neuroinflammatory responses and neuroprotection might be a potential agent for treatment of inflammation-associated disorders.

The osteogenic or adipogenic lineage commitment of human mesenchymal stem cells is determined by protein kinase C delta

BACKGROUND

Mesenchymal stem cells (MSCs) have the potential to differentiate into specialized cell lineages such as osteoblasts and adipocytes in vitro. There exists a reciprocal relationship between osteogenic and adipogenic differentiation of MSCs that an osteogenic phenotype occurs at the expense of an adipogenic phenotype and vice versa, which in turn influence one another's phenotype through negative feedback loops. Thus, it is important to understand what signaling molecules modulate the lineage commitment of MSCs. Protein kinase C (PKC) plays a central role in cellular signal transduction for mediating diverse biological functions, and dysregulation of PKC activity is involved in various metabolic diseases including cancer, diabetes, and heart disease. Although the role of individual PKC isoforms has been investigated in various fields, the potential role of PKC in bone metabolism is not completely understood. In this study, we investigated the potential role of PKCδ in osteogenic lineage commitment of human bone marrow-derived mesenchymal stem cells (hBMSCs).

RESULTS

We observed that expression and phosphorylation of PKCδ were increased during osteogenic differentiation of hBMSCs. Pharmacological inhibition and genetic ablation of PKCδ in hBMSCs resulted in a significant attenuation of osteogenic differentiation as evidenced by reduced ALP activity and ECM mineralization, as well as down-regulation of the expression of osteoblast-specific genes. These effects were also accompanied by induction of adipogenic differentiation and up-regulation of the expression of adipocyte-specific genes involved in lipid synthesis in osteogenic induction of hBMSCs. Additionally, the activation of AMPK, which is a key cellular energy sensor, induced osteogenesis of hBMSCs. However, the inhibition of AMPK activity by compound C did not affect the activation of PKCδ at all, indicating that there is no direct correlation between AMPK and PKCδ in osteogenesis of hBMSCs.

CONCLUSIONS

These results suggest that PKCδ is a critical regulator for the balance between osteogenesis and adipogenesis of hBMSCs and thus has a potential novel therapeutic target for the treatment of metabolic bone diseases.

Preconditioning with endoplasmic reticulum stress ameliorates endothelial cell inflammation

Endoplasmic Reticulum (ER) stress, caused by disturbance in ER homeostasis, has been implicated in several pathological conditions such as ischemic injury, neurodegenerative disorders, metabolic diseases and more recently in inflammatory conditions. Our present study aims at understanding the role of ER stress in endothelial cell (EC) inflammation, a critical event in the pathogenesis of acute lung injury (ALI). We found that preconditioning human pulmonary artery endothelial cells (HPAEC) to ER stress either by depleting ER chaperone and signaling regulator BiP using siRNA, or specifically cleaving (inactivating) BiP using subtilase cytotoxin (SubAB), alleviates EC inflammation. The two approaches adopted to abrogate BiP function induced ATF4 protein expression and the phosphorylation of eIF2α, both markers of ER stress, which in turn resulted in blunting the activation of NF-κB, and restoring endothelial barrier integrity. Pretreatment of HPAEC with BiP siRNA inhibited thrombin-induced IκBα degradation and its resulting downstream signaling pathway involving NF-κB nuclear translocation, DNA binding, phosphorylation at serine536, transcriptional activation and subsequent expression of adhesion molecules. However, TNFα-mediated NF-κB signaling was unaffected upon BiP knockdown. In an alternative approach, SubAB-mediated inactivation of NF-κB was independent of IκBα degradation. Mechanistic analysis revealed that pretreatment of EC with SubAB interfered with the binding of the liberated NF-κB to the DNA, thereby resulting in reduced expression of adhesion molecules, cytokines and chemokines. In addition, both knockdown and inactivation of BiP stimulated actin cytoskeletal reorganization resulting in restoration of endothelial permeability. Together our studies indicate that BiP plays a central role in EC inflammation and injury via its action on NF-κB activation and regulation of vascular permeability.

MiR-135a promotes renal fibrosis in diabetic nephropathy by regulating TRPC1

AIMS/HYPOTHESIS

The contribution of aberrantly expressed microRNAs (miRNAs) to diabetic nephropathy in vivo is poorly understood.

METHODS

Integrated comparative miRNA array profiling was used to examine the expression of serum miRNAs in patients with diabetic nephropathy. The abundance of miRNA-135a (miR-135a) was measured by real-time quantitative PCR in the serum and kidney tissues of patients with diabetic nephropathy. The luciferase assay combined with mutation and immunoblotting was used to screen and verify the bioinformatically predicted miRNAs. Ca(2+) entry or intracellular Ca(2+) ([Ca(2+)]i) was performed by imaging Fura-2/AM-loaded cells using a fluorescence microscopy system. The role of miR-135a in vivo was explored with locked nucleic acid antisense oligonucleotides.

RESULTS

MiR-135a was markedly upregulated in serum and renal tissue from patients with diabetic nephropathy, as well from db/db mice, and this was associated with the development of microalbuminuria and renal fibrosis. Furthermore, we identified transient receptor potential cation channel, subfamily C, member 1 (TRPC1) as a target of miR-135a during renal injury. We demonstrated that overexpression of TRPC1 was able to reverse the pathological effects of miR-135a on promoting proliferation of mesangial cells and increasing synthesis of extracellular matrix proteins. Moreover, miR-135a attenuated store depletion-induced Ca(2+) entry into cells by regulating TRPC1. Importantly, knockdown of miR-135a in diabetic kidneys restored levels of TRPC1 and reduced synthesis of fibronectin and collagen I in vivo. Suppressing TRPC1 levels to prevent Ca(2+) entry into cells may be a mechanism whereby miR-135a promotes renal fibrosis in diabetic kidney injury.

CONCLUSIONS/INTERPRETATION

These findings suggest an important role for miR-135a in renal fibrosis and inhibition of miR-135a might be an effective therapy for diabetic nephropathy.

The transcription factor DREAM represses the deubiquitinase A20 and mediates inflammation

Here we show that the transcription-repressor DREAM binds to the A20 promoter to repress the expression of A20, the deubiquitinase suppressing inflammatory NF-κB signaling. DREAM-deficient (Dream^−/−) mice displayed persistent and unchecked A20 expression in response to endotoxin. DREAM functioned by transcriptionally repressing A20 through binding to downstream regulatory elements (DREs). In contrast, USF1 binding to the DRE-associated E-box domain activated A20 expression in response to inflammatory stimuli. These studies define the critical opposing functions of DREAM and USF1 in inhibiting and inducing A20 expression, respectively, and thereby the strength of NF-κB signaling. Targeting of DREAM to induce USF1-mediated A20 expression is therefore a potential anti-inflammatory strategy in diseases such as acute lung injury associated with unconstrained NF-κB activity.

The TRPC family of TRP channels: roles inferred (mostly) from knockout mice and relationship to ORAI proteins

Aside from entering into cells through voltage gated Ca channels and Na/Ca exchangers in those cells that express these proteins, for all cells be they excitable or non-excitable, Ca(2+) enters through channels that are activated downstream of phosphoinositide mobilization (activation of phospholipase C, PLC) and through channels that are activated secondary to depletion of internal stores. Depletion of internal stores activates plasma membrane channels known as ORAIs. Activation of PLCs activates the canonical class of transient receptor potential channels (TRPCs), and, because this activation also causes depletion of Ca(2+) stores, also ORAI based channels. Whereas the activation of ORAI is a well-accepted phenomenon, it appears that TRPC channels also participate in Ca(2+) entry triggered by store depletion with or without participation of ORAI molecules. Regardless of molecular makeup of TRPC containing channels, a plethora of studies have shown TRPCs to be important both in physiologic systems as well as in pathophysiologic phenomena. Particularly important in defining roles of TRPCs, have been studies with mice with targeted disruption of their genes, i.e., with TRPC KO mice. In this chapter we first focus on TRPCs as regulators of body functions in health and disease, and then focus on the possible make-up of the channels of which they participate. A hypothesis is set forth, whereby ORAI dimers are proposed to be regulatory subunits of tetrameric TRPC channels and serve as structural units that form ORAI channels either as dimers of dimers or trimers of dimers.

TRPC4- and TRPC4-containing channels

TRPC4 proteins comprise six transmembrane domains, a putative pore-forming region, and an intracellularly located amino- and carboxy-terminus. Among eleven splice variants identified so far, TRPC4α and TRPC4β are the most abundantly expressed and functionally characterized. TRPC4 is expressed in various organs and cell types including the soma and dendrites of numerous types of neurons; the cardiovascular system including endothelial, smooth muscle, and cardiac cells; myometrial and skeletal muscle cells; kidney; and immune cells such as mast cells. Both recombinant and native TRPC4-containing channels differ tremendously in their permeability and other biophysical properties, pharmacological modulation, and mode of activation depending on the cellular environment. They vary from inwardly rectifying store-operated channels with a high Ca(2+) selectivity to non-store-operated channels predominantly carrying Na(+) and activated by Gαq- and/or Gαi-coupled receptors with a complex U-shaped current-voltage relationship. Thus, individual TRPC4-containing channels contribute to agonist-induced Ca(2+) entry directly or indirectly via depolarization and activation of voltage-gated Ca(2+) channels. The differences in channel properties may arise from variations in the composition of the channel complexes, in the specific regulatory pathways in the corresponding cell system, and/or in the expression pattern of interaction partners which comprise other TRPC proteins to form heteromultimeric channels. Additional interaction partners of TRPC4 that can mediate the activity of TRPC4-containing channels include (1) scaffolding proteins (e.g., NHERF) that may mediate interactions with signaling molecules in or in close vicinity to the plasma membrane such as Gα proteins or phospholipase C and with the cytoskeleton, (2) proteins in specific membrane microdomains (e.g., caveolin-1), or (3) proteins on cellular organelles (e.g., Stim1). The diversity of TRPC4-containing channels hampers the development of specific agonists or antagonists, but recently, ML204 was identified as a blocker of both recombinant and endogenous TRPC4-containing channels with an IC50 in the lower micromolar range that lacks activity on most voltage-gated channels and other TRPs except TRPC5 and TRPC3. Lanthanides are specific activators of heterologously expressed TRPC4- and TRPC5-containing channels but can block individual native TRPC4-containing channels. The biological relevance of TRPC4-containing channels was demonstrated by knockdown of TRPC4 expression in numerous native systems including gene expression, cell differentiation and proliferation, formation of myotubes, and axonal regeneration. Studies of TRPC4 single and TRPC compound knockout mice uncovered their role for the regulation of vascular tone, endothelial permeability, gastrointestinal contractility and motility, neurotransmitter release, and social exploratory behavior as well as for excitotoxicity and epileptogenesis. Recently, a single-nucleotide polymorphism (SNP) in the Trpc4 gene was associated with a reduced risk for experience of myocardial infarction.

Regulation of ion channels and transporters by AMP-activated kinase (AMPK)

The energy-sensing AMP-activated kinase AMPK ensures survival of energy-depleted cells by stimulating ATP production and limiting ATP utilization. Both energy production and energy consumption are profoundly influenced by transport processes across the cell membane including channels, carriers and pumps. Accordingly, AMPK is a powerful regulator of transport across the cell membrane. AMPK regulates diverse K(+) channels, Na(+) channels, Ca(2+) release activated Ca(2+) channels, Cl(-) channels, gap junctional channels, glucose carriers, Na(+)/H(+)-exchanger, monocarboxylate-, phosphate-, creatine-, amino acid-, peptide- and osmolyte-transporters, Na(+)/Ca(2+)-exchanger, H(+)-ATPase and Na(+)/K(+)-ATPase. AMPK activates ubiquitin ligase Nedd4-2, which labels several plasma membrane proteins for degradation. AMPK further regulates transport proteins by inhibition of Rab GTPase activating protein (GAP) TBC1D1. It stimulates phosphatidylinositol 3-phosphate 5-kinase PIKfyve and inhibits phosphatase and tensin homolog (PTEN) via glycogen synthase kinase 3β (GSK3β). Moreover, it stabilizes F-actin as well as downregulates transcription factor NF-κB. All those cellular effects serve to regulate transport proteins.

Thrombin selectively engages LIM kinase 1 and slingshot-1L phosphatase to regulate NF-κB activation and endothelial cell inflammation

Endothelial cell (EC) inflammation is a central event in the pathogenesis of many pulmonary diseases such as acute lung injury and its more severe form acute respiratory distress syndrome. Alterations in actin cytoskeleton are shown to be crucial for NF-κB regulation and EC inflammation. Previously, we have described a role of actin binding protein cofilin in mediating cytoskeletal alterations essential for NF-κB activation and EC inflammation. The present study describes a dynamic mechanism in which LIM kinase 1 (LIMK1), a cofilin kinase, and slingshot-1Long (SSH-1L), a cofilin phosphatase, are engaged by procoagulant and proinflammatory mediator thrombin to regulate these responses. Our data show that knockdown of LIMK1 destabilizes whereas knockdown of SSH-1L stabilizes the actin filaments through modulation of cofilin phosphorylation; however, in either case thrombin-induced NF-κB activity and expression of its target genes (ICAM-1 and VCAM-1) is inhibited. Further mechanistic analyses reveal that knockdown of LIMK1 or SSH-1L each attenuates nuclear translocation and thereby DNA binding of RelA/p65. In addition, LIMK1 or SSH-1L depletion inhibited RelA/p65 phosphorylation at Ser(536), a critical event conferring transcriptional competency to the bound NF-κB. However, unlike SSH-1L, LIMK1 knockdown also impairs the release of RelA/p65 by blocking IKKβ-dependent phosphorylation/degradation of IκBα. Interestingly, LIMK1 or SSH-1L depletion failed to inhibit TNF-α-induced RelA/p65 nuclear translocation and proinflammatory gene expression. Thus this study provides evidence for a novel role of LIMK1 and SSH-1L in selectively regulating EC inflammation associated with intravascular coagulation.

Store-operated Ca2+ entry (SOCE) induced by protease-activated receptor-1 mediates STIM1 protein phosphorylation to inhibit SOCE in endothelial cells through AMP-activated protein kinase and p38β mitogen-activated protein kinase

The Ca(2+) sensor STIM1 is crucial for activation of store-operated Ca(2+) entry (SOCE) through transient receptor potential canonical and Orai channels. STIM1 phosphorylation serves as an "off switch" for SOCE. However, the signaling pathway for STIM1 phosphorylation is unknown. Here, we show that SOCE activates AMP-activated protein kinase (AMPK); its effector p38β mitogen-activated protein kinase (p38β MAPK) phosphorylates STIM1, thus inhibiting SOCE in human lung microvascular endothelial cells. Activation of AMPK using 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR) resulted in STIM1 phosphorylation on serine residues and prevented protease-activated receptor-1 (PAR-1)-induced Ca(2+) entry. Furthermore, AICAR pretreatment blocked PAR-1-induced increase in the permeability of mouse lung microvessels. Activation of SOCE with thrombin caused phosphorylation of isoform α1 but not α2 of the AMPK catalytic subunit. Moreover, knockdown of AMPKα1 augmented SOCE induced by thrombin. Interestingly, SB203580, a selective inhibitor of p38 MAPK, blocked STIM1 phosphorylation and led to sustained STIM1-puncta formation and Ca(2+) entry. Of the three p38 MAPK isoforms expressed in endothelial cells, p38β knockdown prevented PAR-1-mediated STIM1 phosphorylation and potentiated SOCE. In addition, inhibition of the SOCE downstream target CaM kinase kinase β (CaMKKβ) or knockdown of AMPKα1 suppressed PAR-1-mediated phosphorylation of p38β and hence STIM1. Thus, our findings demonstrate that SOCE activates CaMKKβ-AMPKα1-p38β MAPK signaling to phosphorylate STIM1, thereby suppressing endothelial SOCE and permeability responses.

Genetic disruption of protein kinase Cδ reduces endotoxin-induced lung injury

The pathogenesis of acute lung injury and acute respiratory distress syndrome is characterized by sequestration of leukocytes in lung tissue, disruption of capillary integrity, and pulmonary edema. PKCδ plays a critical role in RhoA-mediated endothelial barrier function and inflammatory responses. We used mice with genetic deletion of PKCδ (PKCδ(-/-)) to assess the role of PKCδ in susceptibility to LPS-induced lung injury and pulmonary edema. Under baseline conditions or in settings of increased capillary hydrostatic pressures, no differences were noted in the filtration coefficients (k(f)) or wet-to-dry weight ratios between PKCδ(+/+) and PKCδ(-/-) mice. However, at 24 h after exposure to LPS, the k(f) values were significantly higher in lungs isolated from PKCδ(+/+) than PKCδ(-/-) mice. In addition, bronchoalveolar lavage fluid obtained from LPS-exposed PKCδ(+/+) mice displayed increased protein and cell content compared with LPS-exposed PKCδ(-/-) mice, but similar changes in inflammatory cytokines were measured. Histology indicated elevated LPS-induced cellularity and inflammation within PKCδ(+/+) mouse lung parenchyma relative to PKCδ(-/-) mouse lungs. Transient overexpression of catalytically inactive PKCδ cDNA in the endothelium significantly attenuated LPS-induced endothelial barrier dysfunction in vitro and increased k(f) lung values in PKCδ(+/+) mice. However, transient overexpression of wild-type PKCδ cDNA in PKCδ(-/-) mouse lung vasculature did not alter the protective effects of PKCδ deficiency against LPS-induced acute lung injury. We conclude that PKCδ plays a role in the pathological progression of endotoxin-induced lung injury, likely mediated through modulation of inflammatory signaling and pulmonary vascular barrier function.

On the role of endothelial TRPC3 channels in endothelial dysfunction and cardiovascular disease

In endothelium, calcium (Ca(2+)) influx through plasma membrane Ca(2+)-permeable channels plays a fundamental role in several physiological functions and in the pathogenesis of cardiovascular disease. Current knowledge on the influence of Ca(2+) influx in signaling events associated to endothelial dysfunction has grown significantly over recent years, particularly after identification of members of the Transient Receptor Potential Canonical (TRPC) family of channel forming proteins as prominent mediators of Ca(2+) entry in endothelial cells. Among TRPC members TRPC3 has been at the center of many of these physiopathological processes. Progress in elucidating the mechanism/s underlying regulation of endothelial TRPC3 and characterization of signaling events downstream TRPC3 activation are of most importance to fully appreciate the role of this peculiar cation channel in cardiovascular disease and its potential use as a therapeutic target. In this updated review we focus on TRPC3 channels, revising and discussing current knowledge on channel expression and regulation in endothelium and the roles of TRPC3 in cardiovascular disease in relation to endothelial dysfunction.

Update on vascular endothelial Ca2+ signalling: A tale of ion channels, pumps and transporters

A monolayer of endothelial cells (ECs) lines the lumen of blood vessels and forms a multifunctional transducing organ that mediates a plethora of cardiovascular processes. The activation of ECs from as state of quiescence is, therefore, regarded among the early events leading to the onset and progression of potentially lethal diseases, such as hypertension, myocardial infarction, brain stroke, and tumor. Intracellular Ca²⁺ signals have long been know to play a central role in the complex network of signaling pathways regulating the endothelial functions. Notably, recent work has outlined how any change in the pattern of expression of endothelial channels, transporters and pumps involved in the modulation of intracellular Ca²⁺ levels may dramatically affect whole body homeostasis. Vascular ECs may react to both mechanical and chemical stimuli by generating a variety of intracellular Ca²⁺ signals, ranging from brief, localized Ca²⁺ pulses to prolonged Ca²⁺ oscillations engulfing the whole cytoplasm. The well-defined spatiotemporal profile of the subcellular Ca²⁺ signals elicited in ECs by specific extracellular inputs depends on the interaction between Ca²⁺ releasing channels, which are located both on the plasma membrane and in a number of intracellular organelles, and Ca²⁺ removing systems. The present article aims to summarize both the past and recent literature in the field to provide a clear-cut picture of our current knowledge on the molecular nature and the role played by the components of the Ca²⁺ machinery in vascular ECs under both physiological and pathological conditions.

Severely blunted allergen-induced pulmonary Th2 cell response and lung hyperresponsiveness in type 1 transient receptor potential channel-deficient mice

Transient receptor potential channels (TRPCs) are widely expressed and regulate Ca²⁺ entry in the cells that participate in the pathophysiology of airway hyperreactivity, inflammation, and remodeling. In vitro studies point to a role for TRPC1-mediated Ca²⁺ signaling in several of these cell types; however, physiological evidence is lacking. Here we identify TRPC1 signaling as proinflammatory and a regulator of lung hyperresponsiveness during allergen-induced pulmonary response. TRPC1-deficient (Trpc1(-/-)) mice are hyposensitive to methacholine challenge and have significantly reduced allergen-induced pulmonary leukocyte infiltration coupled with an attenuated T helper type 2 (Th2) cell response. Upon in vitro allergen exposure, Trpc1(-/-) splenocytes show impaired proliferation and T cell receptor-induced IL-2 production. A high number of germinal centers in spleens of Trpc1(-/-) mice and elevated levels of immunoglobulins in their serum are indicative of dysregulated B cell function and homeostasis. Thus we propose that TRPC1 signaling is necessary in lymphocyte biology and in regulation of allergen-induced lung hyperresponsiveness, making TRPC1 a potential target for treatment of immune diseases and asthma.

Regulation of Orai1/STIM1 by the kinases SGK1 and AMPK

STIM and Orai isoforms orchestrate store operated Ca2+ entry (SOCE) and thus cytosolic Ca2+ fluctuations following stimulation by hormones, growth factors and further mediators. Orai1 is a target of Nedd4-2, an ubiquitin ligase preparing several plasma membrane proteins for degradation. Phosphorylation of Nedd4-2 by the serum and glucocorticoid inducible kinase SGK1 leads to the binding of Nedd4-2 to the protein 14-3-3 thus preventing its interaction with Orai1. Nedd4-2 is activated by the energy sensing AMP activated kinase AMPK. Thus, SGK1 disrupts and AMPK fosters degradation of Orai1. New synthesis of both, Orai1 and STIM1, is stimulated by the transcription factor NF-κB (nuclear factor kappa B), which binds to the respective promoter regions of the genes encoding STIM1 and Orai1. SGK1 upregulates and AMPK presumably downregulates NF-κB and thus de novo synthesis of Orai1 and STIM1 proteins. The regulation by SGK1 links SOCE to the signaling of a wide variety of hormones and growth factors, the AMPK dependent regulation of Orai1 and STIM1 may serve to limit inadequate activation of SOCE following energy depletion, which is otherwise expected to activate SOCE by depletion of intracellular Ca2+ stores due to impairment of the ATP consuming sarco/endoplasmatic reticulum Ca2+ ATPase SERCA.

Enhanced Ca²⁺ entry and Na+/Ca²⁺ exchanger activity in dendritic cells from AMP-activated protein kinase-deficient mice

In dendritic cells (DCs), chemotactic chemokines, such as CXCL12, rapidly increase cytosolic Ca(2+)concentrations ([Ca(2+)](i)) by triggering Ca(2+) release from intracellular stores followed by store-operated Ca(2+) (SOC) entry. Increase of [Ca(2+)](i) is blunted and terminated by Ca(2+) extrusion, accomplished by K(+)-independent Na(+)/Ca(2+) exchangers (NCXs) and K(+)-dependent Na(+)/Ca(2+) exchangers (NCKXs). Increased [Ca(2+)](i) activates energy-sensing AMP-activated protein kinase (AMPK), which suppresses proinflammatory responses of DCs and macrophages. The present study explored whether AMPK participates in the regulation of DC [Ca(2+)](i) and migration. DCs were isolated from AMPKα1-deficient (ampk(-/-)) mice and, as control, from their wild-type (ampk(+/+)) littermates. AMPKα1, Orai1-2, STIM1-2, and mitochondrial calcium uniporter protein expression was determined by Western blotting, [Ca(2+)](i) by Fura-2 fluorescence, SOC entry by inhibition of endosomal Ca(2+) ATPase with thapsigargin (1 μM), Na(+)/Ca(2+) exchanger activity from increase of [Ca(2+)](i), and respective whole-cell current in patch clamp following removal of extracellular Na(+). Migration was quantified utilizing transwell chambers. AMPKα1 protein is expressed in ampk(+/+) DCs but not in ampk(-/-) DCs. CXCL12 (300 ng/ml)-induced increase of [Ca(2+)](i), SOC entry, Orai 1 protein abundance, NCX, and NCKX were all significantly higher in ampk(-/-) DCs than in ampk(+/+) DCs. NCX and NCKX currents were similarly increased in ampk(-/-) DCs. Moreover, CXCL12 (50 ng/ml)-induced DC migration was enhanced in ampk(-/-) DCs. AMPK thus inhibits SOC entry, Na(+)/Ca(2+) exchangers, and migration of DCs.

Down-regulation of CREB-binding protein expression blocks thrombin-mediated endothelial activation by inhibiting acetylation of NF-κB

OBJECTIVES

CREB-binding protein (CBP) belongs to a unique class of transcription co-activators possessing histone acetyltransferase (HAT) activity. The aim of the present study was to evaluate the role of CBP in thrombin-induced endothelial activation, and also explore the underlying mechanism.

METHODS

Leukocyte-endothelial adhesion was calculated as the proportion of the labeled-neutrophils that adhered to ECs relative to all neutrophils applied. Levels of adhesion molecules were analyzed by real-time RT-PCR and western blot. Electrophoretic mobility shift assay and NF-κB reporter assay were performed to evaluate NF-κB activation. Acetylation of NF-κB was measured with immunoprecipitation and western blot assay. To detect the CBP-HAT activity, acetyl residues on an acetylated histone H4 was analyzed.

RESULTS

Leukocyte-endothelial adhesion induced by thrombin was markedly attenuated in endothelial cells with CBP knockdown. The decreased adhesion was paralleled by the reduction of vascular cell adhesion molecule-1, intercellular adhesion molecule-1 and E-selectin. Furthermore, CBP silencing suppressed thrombin-mediated NF-κB activation, and this inhibitory effect was associated with decreased acetylation of NF-κB and CBP-HAT activity.

CONCLUSIONS

Our results indicate that CBP is involved in the regulation of endothelial activation via NF-κB-dependent pathway. Down-regulation of CBP may play a role in returning ECs from a pre-inflammatory status to a quiescent state in the pathogenesis of atherosclerosis.

The Ca(2+) sensor stromal interaction molecule 1 (STIM1) is necessary and sufficient for the store-operated Ca(2+) entry function of transient receptor potential canonical (TRPC) 1 and 4 channels in endothelial cells

We addressed the requirement for stromal interaction molecule 1 (STIM1), the endoplasmic reticulum (ER) Ca(2+)-sensor, and Orai1, a Ca(2+) selective channel, in regulating Ca(2+) entry through the store-operated channels mouse transient receptor potential canonical (TRPC) 4 or human TRPC1. Studies were made using murine and human lung endothelial cells (ECs) challenged with thrombin known to induce Ca(2+) entry via TRPC1/4. Deletion or knockdown of TRPC4 abolished Ca(2+) entry secondary to depletion of ER Ca(2+) stores, preventing the disruption of the endothelial barrier. Knockdown of STIM1 (but not of Orai1or Orai3) or expression of the dominant-negative STIM1(K684E-K685E) mutant in ECs also suppressed Ca(2+) entry secondary to store depletion. Ectopic expression of WT-STIM1 or WT-Orai1 in TRPC4(-/-)-ECs failed to rescue Ca(2+) entry; however, WT-TRPC4 expression in TRPC4(-/-)-ECs restored Ca(2+) entry indicating the requirement for TRPC4 in mediating store-operated Ca(2+) entry. Moreover, expression of the dominant-negative Orai1(R91W) mutant or Orai3(E81W) mutant in WT-ECs failed to prevent thrombin-induced Ca(2+) entry. In contrast, expression of the dominant-negative TRPC4(EE647-648KK) mutant in WT-ECs markedly reduced thrombin-induced Ca(2+) entry. In ECs expressing YFP-STIM1, ER-store Ca(2+) depletion induced formation of fluorescent membrane puncta in WT but not in TRPC4(-/-) cells, indicating that mobilization of STIM1 and engagement of its Ca(2+) sensing function required TRPC4 expression. Coimmunoprecipitation studies showed coupling of TRPC1 and TRPC4 with STIM1 on depletion of ER Ca(2+) stores. Thus, TRPC1 and TRPC4 can interact with STIM1 to form functional store-operated Ca(2+)-entry channels, which are essential for mediating Ca(2+) entry-dependent disruption of the endothelial barrier.

Blocking NF-κB: an inflammatory issue

The nuclear factor (NF)-κB is considered the master regulator of inflammatory responses. Studies in mouse models have established this transcription factor as an important mediator of many inflammatory disease states, including pulmonary diseases such as acute lung injury and acute respiratory distress syndrome. Endothelial cells provide the first barrier for leukocytes migrating to the inflamed sites and hence offer an attractive cellular context for targeting NF-κB for treatment of these diseases. However, recent studies showing that NF-κB also plays an important role in resolution phase of inflammation and in tissue repair and homeostasis have challenged the view of therapeutic inhibition of NF-κB. This article reviews the regulation of NF-κB in the context of endothelial cell signaling and provides a perspective on why "dampening" rather than "abolishing" NF-κB activation may be a safe and effective treatment strategy for inflammation-associated pulmonary and other inflammatory diseases.