phorbol-12-13-didecanoate and Disease-Models--Animal

 Inadequate neovascularization is a major risk factor that can lead to subsequent necrosis of prefabricated flaps. Recent evidence indicates that transient receptor potential cation channel, subfamily V, member 4 (TRPV4) activates growth and remodeling of collateral arteries in ischemia tissues by responding to elevated fluid shear stress (FSS). Therefore, we evaluated whether TRPV4 could increase neovascularization in prefabricated flaps in a rat model..  Rat prefabricated skin flaps were created by ligating the right femoral vascular pedicle and implanting it underneath abdominal flaps. Thirty-six male Sprague-Dawley rats were randomly assigned to three groups with different solutions injected subcutaneously in the implantation site around the pedicle: injected with normal saline as the control group; injected with 4α-Phorbol 12,13-didecanoate (4αPDD), a specific TRPV4 activator, as the 4αPDD group; or injected with ruthenium red (RR), a TRPV-blocker, as the RR group. Neovascularization was evaluated by laser speckle contrast imaging (FLPI), histological staining, and enzyme-linked immunosorbent assay (ELISA) within two weeks. Afterwards, the abdominal island flaps were completely elevated and sutured back. The flap viability and survival area were examined on day 7..  A larger area of flap survival, higher capillary densities, and higher von Willebrand factor (vWF) expression were observed in the 4αPDD group in comparison to those in the other two groups. The secretion of vascular endothelial growth factor (VEGF), but not basic fibroblast growth factor (bFGF), was significantly elevated in the 4αPDD group..  Activation of TRPV4 using 4αPDD can significantly increase the survival of prefabricated flaps via neovascularization inducement, possibly through VEGF secretion enhancement. TRPV4 serves as a potential therapeutic neovascularization target in prefabricated flaps.

Topics: Animals; Disease Models, Animal; Femoral Artery; Free Tissue Flaps; Graft Survival; Male; Neovascularization, Physiologic; Phorbol Esters; Plastic Surgery Procedures; Rats; Rats, Sprague-Dawley; TRPV Cation Channels

In polycystic liver diseases, cyst formation involves cholangiocyte hyperproliferation. In polycystic kidney (PCK) rats, an animal model of autosomal-recessive polycystic kidney disease (ARPKD), decreased intracellular calcium [Ca(2+)](i) in cholangiocytes is associated with hyperproliferation. We recently showed transient receptor potential vanilloid 4 (Trpv4), a calcium-entry channel, is expressed in normal cholangiocytes and its activation leads to [Ca(2+)](i) increase. Thus, we hypothesized that pharmacologic activation of Trpv4 might reverse the hyperproliferative phenotype of PCK cholangiocytes.. Trpv4 expression was examined in liver of normal and PCK rats, normal human beings, and patients with autosomal-dominant polycystic kidney disease or ARPKD. Trpv4 activation effect on cell proliferation and cyst formation was assessed in cholangiocytes derived from normal and PCK rats. The in vivo effects of Trpv4 activation on kidney and liver cysts was analyzed in PCK rats.. Trpv4 was overexpressed both at messenger RNA (8-fold) and protein (3-fold) levels in PCK cholangiocytes. Confocal and immunogold electron microscopy supported Trpv4 overexpression in the livers of PCK rats and ARPKD or autosomal-dominant polycystic kidney disease patients. Trpv4 activation in PCK cholangiocytes increased [Ca(2+)](i) by 30%, inhibiting cell proliferation by approximately 25%-50% and cyst growth in 3-dimensional culture (3-fold). Trpv4-small interfering RNA silencing blocked effects of Trpv4 activators by 70%. Trpv4 activation was associated with Akt phosphorylation and beta-Raf and Erk1/2 inhibition. In vivo, Trpv4 activation induced a significant decrease in renal cystic area and a nonsignificant decrease in liver cysts.. Taken together, our in vitro and in vivo data suggest that increasing intracellular calcium by Trpv4 activation may represent a potential therapeutic approach in PKD.

Topics: Animals; Bile Ducts; Calcium; Cell Proliferation; Disease Models, Animal; Extracellular Signal-Regulated MAP Kinases; Humans; Leucine; Phenotype; Phorbol Esters; Polycystic Kidney, Autosomal Recessive; Proto-Oncogene Proteins B-raf; Proto-Oncogene Proteins c-akt; Rats; Rats, Sprague-Dawley; Signal Transduction; Sulfonamides; TRPV Cation Channels

To test the hypothesis that activation of the transient receptor potential vanilloid 4 (TRPV4) channel conveys a hypotensive effect that is enhanced during salt load, male Wistar rats fed a normal-sodium (0.5%) or high-sodium (HS; 4%) diet for 3 weeks were given 4 alpha-phorbol 12,13-didecanoate (4 alpha-PDD), a specific TRPV4 activator, in the presence or absence of capsazepine, a selective TRPV1 blocker, ruthenium red, a TRPV4 blocker, or TRPV4 small hairpin RNA that selectively knockdowns TRPV4. 4 alpha-PDD (1, 2.5, or 5 mg/kg IV) dose-dependently decreased mean arterial pressure (P<0.05). HS enhanced 4 alpha-PDD-induced depressor effects as well as 4 alpha-PDD-mediated release of calcitonin gene-related peptide and substance P (P<0.001). Ruthenium red markedly blunted (P<0.001), whereas capsazepine slightly attenuated (P<0.05) 4 alpha-PDD-induced depressor effects in HS and normal-sodium diet rats. Ruthenium red alone increased baseline mean arterial pressure in both HS and normal-sodium diet rats with a greater magnitude in the former (P<0.05). Western blot analysis showed that HS increased TRPV4 expression in dorsal root ganglia and mesenteric arteries (P<0.05) but not the renal cortex and medulla. Gene-silencing approach revealed that TRPV4 small hairpin RNA downregulated TRPV4 expression leading to blunted 4 alpha-PDD-induced hypotension (P<0.05). Thus, TRPV4 activation decreases blood pressure in rats given a normal-sodium diet. HS enhances TRPV4 expression in sensory nerves/mesenteric arteries and TRPV4-mediated depressor effects and calcitonin gene-related peptide/substance P release such that HS causes a greater increase in blood pressure when TRPV4 is blocked. Our data indicate that TRPV4 activation may constitute a compensatory mechanism in preventing salt-induced increases in blood pressure.

Topics: Animals; Blood Pressure; Calcitonin Gene-Related Peptide; Capsaicin; Disease Models, Animal; Dose-Response Relationship, Drug; Ganglia, Spinal; Hypertension; Hypotension; Kidney; Male; Mesenteric Arteries; Phorbol Esters; Rats; Rats, Wistar; Ruthenium Red; Salt Tolerance; Sodium Chloride, Dietary; Substance P; TRPV Cation Channels

In acute respiratory distress syndrome, pulmonary vascular permeability increases, causing intravascular fluid and protein to move into the lung's interstitium. The classic model describing the formation of pulmonary edema suggests that fluid crossing the capillary endothelium is drawn by negative interstitial pressure into the potential space surrounding extra-alveolar vessels and, as interstitial pressure builds, is forced into the alveolar air space. However, the validity of this model is challenged by animal models of acute lung injury in which extra-alveolar vessels are more permeable than capillaries under a variety of conditions. In the current study, we sought to determine whether extravascular fluid accumulation can be produced because of increased permeability of either the capillary or extra-alveolar endothelium, and whether different pathophysiology results from such site-specific increases in permeability.. We perfused isolated lungs with either the plant alkaloid thapsigargin, which increases extra-alveolar endothelial permeability, or with 4alpha-phorbol 12, 13-didecanoate, which increases capillary endothelial permeability.. Both treatments produced equal increases in whole lung vascular permeability, but caused fluid accumulations in separate anatomical compartments. Light microscopy of isolated lungs showed that thapsigargin caused fluid cuffing of large vessels, while 4alpha-phorbol 12, 13-didecanoate caused alveolar flooding. Dynamic compliance was reduced in lungs with cuffing of large vessels, but not in lungs with alveolar flooding.. Phenotypic differences between vascular segments resulted in site-specific increases in permeability, which have different pathophysiological outcomes. Our findings suggest that insults leading to acute respiratory distress syndrome may increase permeability in extra-alveolar or capillary vascular segments, resulting in different pathophysiological sequela.

Topics: Animals; Carcinogens; Cell Membrane Permeability; Disease Models, Animal; Endothelial Cells; Enzyme Inhibitors; Extravascular Lung Water; Lung; Lung Compliance; Male; Phorbol Esters; Pulmonary Alveoli; Pulmonary Edema; Rats; Rats, Sprague-Dawley; Respiratory Distress Syndrome; Respiratory Mechanics; Thapsigargin