Piper sarmentosum Roxb. Inhibits Angiotensin-Converting Enzyme Activity in Phorbol 12-Myristate-13-Acetate-Induced Endothelial Cells.

Angiotensin-converting enzyme (ACE) plays a crucial role in the pathogenesis of hypertension. Piper sarmentosum Roxb., an herb known for its antihypertensive effect, lacks a comprehensive understanding of the mechanism underlying its antihypertensive action. This study aimed to elucidate the antihypertensive mechanism of aqueous extract of P. sarmentosum leaves (AEPS) via its modulation of the ACE pathway in phorbol 12-myristate-13-acetate (PMA)-induced human umbilical vein endothelial cells (HUVECs). HUVECs were divided into five groups: control, treatment with 200 µg/mL AEPS, induction 200 nM PMA, concomitant treatment with 200 nM PMA and 200 µg/mL AEPS, and treatment with 200 nM PMA and 0.06 µM captopril. Subsequently, ACE mRNA expression, protein level and activity, angiotensin II (Ang II) levels, and angiotensin II type 1 receptor (AT1R) and angiotensin II type 2 receptor (AT2R) mRNA expression in HUVECs were determined. AEPS successfully inhibited ACE mRNA expression, protein and activity, and angiotensin II levels in PMA-induced HUVECs. Additionally, AT1R expression was downregulated, whereas AT2R expression was upregulated. In conclusion, AEPS reduces the levels of ACE mRNA, protein and activity, Ang II, and AT1R expression in PMA-induced HUVECs. Thus, AEPS has the potential to be developed as an ACE inhibitor in the future.

Synthesis and anti-HIV activities of phorbol derivatives.

In this study, 37 derivatives of phorbol esters were synthesized and their anti-HIV-1 activities evaluated, building upon our previous synthesis of 51 phorbol derivatives. 12-Para-electron-acceptor-trans-cinnamoyl-13-decanoyl phorbol derivatives stood out, demonstrating remarkable anti-HIV-1 activities and inhibitory effects on syncytia formation. These derivatives exhibited a higher safety index compared with the positive control drug. Among them, 12-(trans-4-fluorocinnamoyl)-13-decanoyl phorbol, designated as compound 3c, exhibited the most potent anti-HIV-1 activity (EC50 2.9 nmol·L-1, CC50/EC50 11 117.24) and significantly inhibited the formation of syncytium (EC50 7.0 nmol·L-1, CC50/EC50 4891.43). Moreover, compound 3c is hypothesized to act both as an HIV-1 entry inhibitor and as an HIV-1 reverse transcriptase inhibitor. Isothermal titration calorimetry and molecular docking studies indicated that compound 3c may also function as a natural activator of protein kinase C (PKC). Therefore, compound 3c emerges as a potential candidate for developing new anti-HIV drugs.

Role of Protein Kinase C in Metabolic Regulation of Coronary Endothelial Small Conductance Calcium-Activated Potassium Channels.

BACKGROUND: Small conductance calcium-activated potassium (SK) channels are largely responsible for endothelium-dependent coronary arteriolar relaxation. Endothelial SK channels are downregulated by the reduced form of nicotinamide adenine dinucleotide (NADH), which is increased in the setting of diabetes, yet the mechanisms of these changes are unclear. PKC (protein kinase C) is an important mediator of diabetes-induced coronary endothelial dysfunction. Thus, we aimed to determine whether NADH signaling downregulates endothelial SK channel function via PKC. METHODS AND RESULTS: SK channel currents of human coronary artery endothelial cells were measured by whole cell patch clamp method in the presence/absence of NADH, PKC activator phorbol 12-myristate 13-acetate, PKC inhibitors, or endothelial PKCα/PKCß knockdown by using small interfering RNA. Human coronary arteriolar reactivity in response to the selective SK activator NS309 was measured by vessel myography in the presence of NADH and PKCß inhibitor LY333531. NADH (30-300 µmol/L) or PKC activator phorbol 12-myristate 13-acetate (30-300 nmol/L) reduced endothelial SK current density, whereas the selective PKCᵦ inhibitor LY333531 significantly reversed the NADH-induced SK channel inhibition. PKCß small interfering RNA, but not PKCα small interfering RNA, significantly prevented the NADH- and phorbol 12-myristate 13-acetate-induced SK inhibition. Incubation of human coronary artery endothelial cells with NADH significantly increased endothelial PKC activity and PKCß expression and activation. Treating vessels with NADH decreased coronary arteriolar relaxation in response to the selective SK activator NS309, and this inhibitive effect was blocked by coadministration with PKCß inhibitor LY333531. CONCLUSIONS: NADH-induced inhibition of endothelial SK channel function is mediated via PKCß. These findings may provide insight into novel therapeutic strategies to preserve coronary microvascular function in patients with metabolic syndrome and coronary disease.

Isolation, Synthesis, and Structure-Activity Relationship Study on Daphnane and Tigliane Diterpenes as HIV Latency-Reversing Agents.

Three new diterpenes, stellejasmins A (1) and B (2) and 12-O-benzoylphorbol-13-heptanoate (3), were isolated from the roots of Stellera chamaejasme L. The structures of 1-3 were elucidated by extensive NMR and mass spectroscopic analyses. Compounds 1 and 2 are the first derivatives containing a hydroxy group at C-2 in the family of daphnane and tigliane diterpenes. The presence of a chlorine atom in 1 is unique in the plant metabolite. Compound 3 has an odd-number acyl group, which is biosynthetically notable. Human immunodeficiency virus (HIV) LTR-driven transcription activity was tested with 1-3 and 17 known diterpenes isolated from S. chamaejasme L. and Wikstroemia retusa A.Gray. Among these, gnidimacrin (4), stelleralide A (5), and wikstroelide A (20) were highly potent, with EC50 values of 0.14, 0.33, and 0.39 nM, respectively. The structure-activity relationship (SAR) was investigated using 20 natural and eight synthetic diterpenes. This is the first SAR study on natural daphnane and tigliane diterpenes.

LC-MS Identification, Isolation, and Structural Elucidation of Anti-HIV Tigliane Diterpenoids from Wikstroemia lamatsoensis.

Structurally diverse tigliane diterpenoids have drawn significant research interest for drug discovery over many decades. Using LC-MS-guided fractionation and separation, the first phytochemical investigation on Wikstroemia lamatsoensis led to the isolation of eight tiglianes (1-8), including two new compounds, wikstrocin D (1) and wikstrocin E (2). The new structures were elucidated based on extensive physicochemical and spectroscopic analyses. The characteristic ESIMS/MS fragmentations of tiglianes 1-8 were also summarized. Among the isolated tiglianes, three compounds (8, 5, and 7) showed the most potent anti-HIV activity, with IC50 values of 0.18, 3.8, and 12.8 nM, respectively.

Anti-HIV Tigliane Diterpenoids from Wikstroemia scytophylla.

During a chemical investigation of Wikstroemia scytophylla, three new [wikstrocins A-C (1-3)] and three known tigliane diterpenoids (4-6) were isolated. The structures of the new compounds were elucidated from extensive physiochemical and spectroscopic analysis. The correlations between the ECD Cotton effects and B ring structures of tiglianes were also evaluated. The isolated compounds were assessed for their anti-HIV activity against HIV-1 infection of MT4 cells, and two compounds (4 and 6) showed potent anti-HIV activity with IC50 values of 3.8 and 12.8 nM, respectively.

Novel epoxy-tiglianes stimulate skin keratinocyte wound healing responses and re-epithelialization via protein kinase C activation.

Epoxy-tiglianes are a novel class of diterpene esters. The prototype epoxy-tigliane, EBC-46 (tigilanol tiglate), possesses potent anti-cancer properties and is currently in clinical development as a local treatment for human and veterinary cutaneous tumors. EBC-46 rapidly destroys treated tumors and consistently promotes wound re-epithelialization at sites of tumor destruction. However, the mechanisms underlying these keratinocyte wound healing responses are not completely understood. Here, we investigated the effects of EBC-46 and an analogue (EBC-211) at 1.51 nM-151 µM concentrations, on wound healing responses in immortalized human skin keratinocytes (HaCaTs). Both EBC-46 and EBC-211 (1.51 nM-15.1 µM) accelerated G0/G1-S and S-G2/M cell cycle transitions and HaCaT proliferation. EBC-46 (1.51-151 nM) and EBC-211 (1.51 nM-15.1 µM) further induced significant HaCaT migration and scratch wound repopulation. Stimulated migration/wound repopulation responses were even induced by EBC-46 (1.51 nM) and EBC-211 (1.51-151 nM) with proliferation inhibitor, mitomycin C (1 µM), suggesting that epoxy-tiglianes can promote migration and wound repopulation independently of proliferation. Expression profiling analyses showed that epoxy-tiglianes modulated keratin, DNA synthesis/replication, cell cycle/proliferation, motility/migration, differentiation, matrix metalloproteinase (MMP) and cytokine/chemokine gene expression, to facilitate enhanced responses. Although epoxy-tiglianes down-regulated established cytokine and chemokine agonists of keratinocyte proliferation and migration, enhanced HaCaT responses were demonstrated to be mediated via protein kinase C (PKC) phosphorylation and significantly abrogated by pan-PKC inhibitor, bisindolylmaleimide-1 (BIM-1, 1 µM). By identifying how epoxy-tiglianes stimulate keratinocyte healing responses and re-epithelialization in treated skin, our findings support the further development of this class of small molecules as potential therapeutics for other clinical situations associated with impaired re-epithelialization, such as non-healing skin wounds.

Recent advances in TRPV4 agonists and antagonists.

TRPV4 is a ubiquitously expressed, non-selective cation channel activated by a range of stimuli including hypotonicity, temperature, pH, stretch and endogenous ligands. Agents that modulate TRPV4 are sought as potential therapeutics for the treatment of many diseases including osteoarthritis, respiratory illnesses, gastrointestinal disorders, pain and congestive heart failure. In recent years, significant advances in TRPV4 drug discovery have been realized as at least seven novel TRPV4 agonist or antagonist templates were reported and the first selective TRPV4 antagonist was evaluated in early clinical trials.

A Potential Nutraceutical Candidate Lactucin Inhibits Adipogenesis through Downregulation of JAK2/STAT3 Signaling Pathway-Mediated Mitotic Clonal Expansion.

The prevalence of obesity has increased dramatically worldwide in the past ~50 years. Searching for safe and effective anti-obesity strategies are urgently needed. Lactucin, a plant-derived natural small molecule, is known for anti-malaria and anti-hyperalgesia. The study is to investigate whether lactucin plays a key role in adipogenesis. To this end, in vivo male C57BL/6 mice fed a high-fat diet (HFD) were treated with 20 mg/kg/day of lactucin or vehicle by gavage for seven weeks. Compared with vehicle-treated controls, Lactucin-treated mice showed lower body mass and mass of adipose tissue. Consistently, in vitro 3T3-L1 cells were treated with 20 µM of lactucin. Compared to controls, lactucin-treated cells showed significantly less lipid accumulation during adipocyte differentiation and lower levels of lipid synthesis markers. Mechanistically, we showed the anti-adipogenic property of lactucin was largely limited to the early stage of adipogenesis. Lactucin-treated cells fail to undergo mitotic clonal expansion (MCE). Further studies demonstrate that lactucin-induced MCE arrests might result from reduced phosphorylation of JAK2 and STAT3. We then asked whether activation of JAK2/STAT3 would restore the inhibitory effect of lactucin on adipogenesis with pharmacological STAT3 activator colivelin. Our results revealed similar levels of lipid accumulation between lactucin-treated cells and controls in the presence of colivelin, indicating that inactivation of STAT3 is the limiting factor for the anti-adipogenesis of lactucin in these cells. Together, our results provide the indication that lactucin exerts an anti-adipogenesis effect, which may open new therapeutic options for obesity.

Effectiveness of the Sleep Enhancement by Green Romaine Lettuce (Lactuca sativa) in a Rodent Model.

This study was conducted to investigate the effects of the extracts of green romaine lettuce (GRE) on sleep enhancement. GRE contains 1071.7 and 199.2 µg/g of extracts of lactucin and lactucopicrin, respectively, known as sleep enhancement substances. When 100 mg/kg of GRE was administered orally, sleep latency and duration time were significantly increased compared to controls (p < 0.05). Rapid eye movement (REM) sleep decreased with 100 mg/kg of GRE administration and non-REM (NREM) sleep also increased. There was no significant difference between REM and NREM among the oral GRE administration groups receiving 100, 120, and 160 mg/kg GRE. In the caffeine-induced insomnia model, total sleep time was significantly increased by 100 mg/kg GRE administration compared to the caffeine-treated group (p < 0.05). In addition, GRE inhibited the binding of [3H]-flumazenil in a concentration-dependent manner, and affinity of both lactucin and lactucopicrin to gamma-aminobutyric acid (GABA)A-benzodiazepine (BDZ) receptor was 80.7% and 55.9%, respectively. Finally, in the pentobarbital-induced sleep mouse model, the sleep enhancement effect of GRE was inhibited by flumazenil, an antagonist of BDZ. Thus, these results demonstrate that GRE acts via a GABAergic mechanism to promote sleep in a rodent model.

Tigliane Diterpenoids as a New Type of Antiadipogenic Agents Inhibit GRα-Dexras1 Axis in Adipocytes.

The phytochemical study of Euphorbia prolifera led to the isolation of two tiglianes (1 and 2) and 23 mysrinanes (3-25). Most of these isolates showed significant antiadipogenic activity in 3T3-L1 adipocyte without apparent cytotoxicity. Subsequent structural modification yielded 10 derivatives, among which 1a, the 5- O-acetyl derivative of 1, turned out to be the most active compound with improved triglyceride-lowering activity (EC50 for 1 and 1a: 0.61 and 0.32 µM, respectively) and reduced cytotoxicity (selectivity index for 1 and 1a: 28 and 312, respectively). The structure-activity relationship study revealed that the trans-fused 5/7/6 ring system in an angular shape was important to the activity. A mechanistic study indicated that 1 and 1a could inhibit the glucocorticoid receptor α-Dexras1 axis in adipocyte, leading to the retardation of cell differentiation at the early stage. These findings may provide a new type of lipid-lowering agents for future antiobesity drug development.

Downregulation of endothelial transient receptor potential vanilloid type 4 channel underlines impaired endothelial nitric oxide-mediated relaxation in the mesenteric arteries of hypertensive rats.

The endothelium contributes to the maintenance of vasodilator tone by releasing endothelium-derived relaxing factors, including nitric oxide (NO). In hypertension, endothelial nitric oxide synthase (eNOS) produces less NO and could be one of the contributing factors to the increased peripheral vascular resistance. Agonist-induced Ca(2+) entry is essential for the activation of eNOS. The transient receptor potential vanilloid type 4 (TRPV4) channel, a Ca(2+)-permeant cation channel, is expressed in the endothelial cells and involved in the regulation of vascular tone. The present study aimed to investigate the role of TRPV4 channel in endothelium-dependent NO-mediated relaxation of the resistance artery in hypertensive rats. Using a wire myograph, relaxation response to the TRPV4 activator, 4alpha-phorbol-12,13-didecanoate (4alphaPDD) was assessed in mesenteric arteries obtained from Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHRs). Compared to WKY, SHR demonstrated a significantly attenuated 4alphaPDD-induced endothelium-dependent NO-mediated relaxation. Immunohistochemical analysis revealed positive staining for TRPV4 in the endothelium of mesenteric artery sections in both WKY and SHR. Furthermore, TRPV4 mRNA and protein expressions in SHR were significantly lower than their expression levels in WKY rats. We conclude that 4alphaPDD-induced endothelium-dependent NO-mediated vasorelaxation is reduced in SHR and downregulation of TRPV4 could be one of the contributing mechanisms.

Insights Into the Different Effects of Food on Intestinal Secretion Using Magnetic Resonance Imaging.

BACKGROUND: Plant foods may stimulate intestinal secretion through chemicals designed to deter herbivores, including lactucins in lettuce and rhein in rhubarb. This may increase ileostomy output and induce diarrhoea in people with intact bowels. OBJECTIVE: We aimed to determine the effect of food on intestinal water content using Magnetic Resonance Imaging (MRI). DESIGN: A three period crossover trial of isocaloric meals in adults without bowel disorders. Meals: 2 slices white bread with 10 g butter; 300 g rhubarb with 60 mL lactose free cream; 300 g lettuce with 30 mL mayonnaise. PRIMARY OUTCOME: Area under curve (AUC) small bowel water content (SBWC) using MRI. SECONDARY OUTCOMES: ascending colon water content; T1 relaxation time of ascending colon (T1AC); gastric volume; visual analogue scales of bloating and satiety (0-100). MRI analysts were blinded. Scanned fasting and hourly to 180 min postprandial. Symptoms scored half-hourly. RESULTS: 9 female and 6 male subjects completed the study. AUC SBWC fell after bread but rose after lettuce and even more after rhubarb, difference from baseline being (Bread AUC -5662 (1209) ml.min vs Lettuce 3194 (1574) ml.min and Rhubarb 10586 (1629) ml.min (P < 0.01). Rhubarb induced a rise in T1AC but differences at 3 hours were not significant (P = 0.06). Gastric volume at T = 0 significantly was higher for both lettuce and rhubarb (571 ± 92 and 558 ± 89 mls) respectively compared to bread (314 ± 108 mls) (p < 0.0001). Symptom scores were higher for lettuce > rhubarb > bread. CONCLUSION: Lettuce and rhubarb meals increased intestinal water content, demonstrating how different foods can alter ileal flow and stool consistency.

Omega-3 Fatty Acids Modulate TRPV4 Function through Plasma Membrane Remodeling.

Dietary consumption of ω-3 polyunsaturated fatty acids (PUFAs), present in fish oils, is known to improve the vascular response, but their molecular targets remain largely unknown. Activation of the TRPV4 channel has been implicated in endothelium-dependent vasorelaxation. Here, we studied the contribution of ω-3 PUFAs to TRPV4 function by precisely manipulating the fatty acid content in Caenorhabditis elegans. By genetically depriving the worms of PUFAs, we determined that the metabolism of ω-3 fatty acids is required for TRPV4 activity. Functional, lipid metabolome, and biophysical analyses demonstrated that ω-3 PUFAs enhance TRPV4 function in human endothelial cells and support the hypothesis that lipid metabolism and membrane remodeling regulate cell reactivity. We propose a model whereby the eicosanoid's epoxide group location increases membrane fluidity and influences the endothelial cell response by increasing TRPV4 channel activity. ω-3 PUFA-like molecules might be viable antihypertensive agents for targeting TRPV4 to reduce systemic blood pressure.

Identification of proximal biomarkers of PKC agonism and evaluation of their role in HIV reactivation.

DESIGN: The HIV latent CD4+ T cell reservoir is broadly recognized as a barrier to HIV cure. Induction of HIV expression using protein kinase C (PKC) agonists is one approach under investigation for reactivation of latently infected CD4+ T cells (Beans et al., 2013; Abreu et al., 2014; Jiang et al., 2014; Jiang and Dandekar, 2015). We proposed that an increased understanding of the molecular mechanisms of action of PKC agonists was necessary to inform on biological signaling and pharmacodynamic biomarkers. RNA sequencing (RNA Seq) was applied to identify genes and pathways modulated by PKC agonists. METHODS: Human CD4+ T cells were treated ex vivo with Phorbol 12-myristate 13-acetate, prostatin or ingenol-3-angelate. At 3 h and 24 h post-treatment, cells were harvested and RNA-Seq was performed on RNA isolated from cell lysates. The genes differentially expressed across the PKC agonists were validated by quantitative RT-PCR (qPCR). A subset of genes was evaluated for their role in HIV reactivation using siRNA and CRISPR approaches in the Jurkat latency cell model. RESULTS: Treatment of primary human CD4+ T cells with PKC agonists resulted in alterations in gene expression. qPCR of RNA Seq data confirmed upregulation of 24 genes, including CD69, Egr1, Egr2, Egr3, CSF2, DUSP5, and NR4A1. Gene knockdown of Egr1 and Egr3 resulted in reduced expression and decreased HIV reactivation in response to PKC agonist treatment, indicating a potential role for Egr family members in latency reversal. CONCLUSION: Overall, our results offer new insights into the mechanism of action of PKC agonists, biomarkers of pathway engagement, and the potential role of EGR family in HIV reactivation.

Functional Expression of an Osmosensitive Cation Channel, Transient Receptor Potential Vanilloid 4, in Rat Vestibular Ganglia.

Transient receptor potential vanilloid (TRPV) 4 is a nonselective cation channel expressed in sensory neurons such as those in the dorsal root and trigeminal ganglia, kidney, and inner ear. TRPV4 is activated by mechanical stress, heat, low osmotic pressure, low pH, and phorbol derivatives such as 4α-phorbol 12,13-didecanoate (4α-PDD). We investigated the expression of TRPV4 in rat vestibular ganglion (VG) neurons. The TRPV4 gene was successfully amplified from VG neuron mRNA using reverse-transcription polymerase chain reaction. Furthermore, immunoblotting showed positive expression of TRPV4 protein in VG neurons. Immunohistochemistry indicated that TRPV4 was localized predominantly on the plasma membrane of VG neurons. Calcium (Ca2+) imaging of VG neurons showed that 4α-PDD and/or hypotonic stimuli caused an increase in intracellular Ca2+ concentration ([Ca2+]i) that was almost completely inhibited by ruthenium red, a selective antagonist of TRPV channels. Interestingly, a [Ca2+]i increase was evoked by both hypotonic stimuli and 4α-PDD in approximately 38% of VG neurons. These data indicate that TRPV4 is functionally expressed in VG neurons as an ion channel and that TRPV4 likely participates in VG neurons for vestibular neurotransmission as an osmoreceptor and/or mechanoreceptor.

Ca(2+) influx mediates the TRPV4-NO pathway in neuropathic hyperalgesia following chronic compression of the dorsal root ganglion.

Chronic compression of the dorsal root ganglion (DRG) (CCD) in rats is a typical model of neuropathic pain. TRPV4 contributed to mechanical allodynia induced by the CCD model. Our previous study demonstrated that TRPV4 enhances neuropathic hyperalgesia through a NO-cGMP-PKG cascade. However, the underlying mechanism(s) is still largely unknown. Therefore, the aim of the present study was to test whether TRPV4-mediated Ca(2+) influx is involved in the TRPV4-NO pathway. Regulation of intracellular calcium concentration by intrathecal injection of TRPV4-targeted siRNA significantly decreased the behavioural hyperalgesia, NF-κB activity, and NO content in CCD rats. Intraperitoneal (i.p.) injection of mibefradil significantly induced dose-dependent increases in the paw withdrawal latency (PWL) and mechanical withdrawal thresholds (MWT), as well as decreases in NF-κB activity and NO content in DRG of CCD rats. Moreover, pre-treatment with 4α-PDD attenuated the suppressive effects of mibefradil on CCD-induced neuropathic hyperalgesia, NF-κB activity, and NO production. The data showed that TRPV4-mediated Ca(2+) influx might be engaged in the TRPV4-NO pathway in neuropathic hyperalgesia in the CCD model.

Hypotonic stress induces RANKL via transient receptor potential melastatin 3 (TRPM3) and vaniloid 4 (TRPV4) in human PDL cells.

Bone remodeling occurs in response to various types of mechanical stress. The periodontal ligament (PDL) plays an important role in mechanical stress-mediated alveolar bone remodeling. However, the underlying mechanism at the cellular level has not been extensively studied. In this study, we investigated the effect of shear stress on the expression of bone remodeling factors, including receptor activator of nuclear factor-kappa B (NF-κB) ligand (RANKL) and osteoprotegerin (OPG), as well as its upstream signaling pathway in primary human PDL cells. We applied hypotonic stress to reproduce shear stress to PDL cells. Hypotonic stress induced the messenger RNA (mRNA) and protein expression of RANKL but not OPG. It also increased intracellular Ca(2+) concentration ([Ca(2+)]i). Extracellular Ca(2+) depletion and nonspecific plasma membrane Ca(2+) channel blockers completely inhibited the increase in both [Ca(2+)]i and RANKL mRNA expression. We identified the expression and activation of transient receptor potential melastatin 3 (TRPM3) and vaniloid 4 (TRPV4) channels in PDL cells. Pregnenolone sulfate (PS) and 4α-phorbol 12, 13-didecanoate (4α-PDD), which are agonists of TRPM3 and TRPV4, augmented Ca(2+) influx and RANKL mRNA expression. Both pharmacological (2-aminoethoxydiphenyl borate [2-APB], ruthenium red [RR], ononetin [Ono], and HC 067047 [HC]) and genetic (small interfering RNA [siRNA]) inhibitors of TRPM3 and TRPV4 reduced the hypotonic stress-mediated increase in [Ca(2+)]i and RANKL mRNA expression. Our study shows that hypotonic stress induced RANKL mRNA expression via TRPM3- and TRPV4-mediated extracellular Ca(2+) influx and RANKL expression. This signaling pathway in PDL cells may play a critical role in mechanical stress-mediated alveolar bone remodeling.

Synthesis of a des-B-ring bryostatin analogue leads to an unexpected ring expansion of the bryolactone core.

A convergent synthesis of a des-B-ring bryostatin analogue is described. This analogue was found to undergo an unexpected ring expansion of the bryolactone core to generate the corresponding 21-membered macrocycle. The parent analogue and the ring-expanded product both displayed nanomolar binding affinity for PKC. Despite containing A-ring substitution identical to that of bryostatin 1 and displaying bryostatin-like biological function, the des-B-ring analogues displayed a phorbol-like biological function in cells. These studies shed new light on the role of the bryostatin B-ring in conferring bryo-like biological function to bryostatin analogues.

A novel subtype of astrocytes expressing TRPV4 (transient receptor potential vanilloid 4) regulates neuronal excitability via release of gliotransmitters.

Astrocytes play active roles in the regulation of synaptic transmission. Neuronal excitation can evoke Ca(2+) transients in astrocytes, and these Ca(2+) transients can modulate neuronal excitability. Although only a subset of astrocytes appears to communicate with neurons, the types of astrocytes that can regulate neuronal excitability are poorly characterized. We found that ∼30% of astrocytes in the brain express transient receptor potential vanilloid 4 (TRPV4), indicating that astrocytic subtypes can be classified on the basis of their expression patterns. When TRPV4(+) astrocytes are activated by ligands such as arachidonic acid, the activation propagates to neighboring astrocytes through gap junctions and by ATP release from the TRPV4(+) astrocytes. After activation, both TRPV4(+) and TRPV4(-) astrocytes release glutamate, which acts as an excitatory gliotransmitter to increase synaptic transmission through type 1 metabotropic glutamate receptor (mGluR). Our results indicate that TRPV4(+) astrocytes constitute a novel subtype of the population and are solely responsible for initiating excitatory gliotransmitter release to enhance synaptic transmission. We propose that TRPV4(+) astrocytes form a core of excitatory glial assembly in the brain and function to efficiently increase neuronal excitation in response to endogenous TRPV4 ligands.