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Characterization of biosynthesis and modes of action of prostaglandin E2 and prostacyclin in guinea pig mesenteric lymphatic vessels.

ABSTRACT: Rhythmical transient constrictions of the lymphatic vessels provide the means for efficient lymph drainage and interstitial tissue fluid balance. This activity is critical during inflammation, to avoid or limit oedema resulting from increased vascular permeability, mediated by the release of various inflammatory mediators. In this study, we investigated the mechanisms by which prostaglandin E(2) (PGE(2)) and prostacyclin modulate lymphatic contractility in isolated guinea pig mesenteric lymphatic vessels.Quantitative RT-PCR was used to assess the expression of mRNA for enzymes and receptors involved in the production and action of PGE(2) and prostacyclin in mesenteric collecting lymphatic vessels. Frequency and amplitude of lymphatic vessel constriction were measured in the presence of these prostaglandins and the role of their respective EP and IP receptors assessed.Prostaglandin E(2) and prostacyclin decreased concentration-dependently the frequency, without affecting the amplitude, of lymphatic constriction. Data obtained in the presence of the EP(4) receptor antagonists, GW627368x (1 microM) and AH23848B (30 microM) and the IP receptor antagonist CAY10441 (0.1 microM) suggest that PGE(2) predominantly activates EP(4), whereas prostacyclin mainly stimulates IP receptors. Inhibition of responses to either prostaglandin with H89 (10 microM) or glibenclamide (1 microM) suggested a role for the activation of protein kinase A and ATP-sensitive K(+) channels.Our findings characterized the inhibition of lymphatic pumping induced by PGE(2) or prostacyclin in guinea pig mesenteric lymphatics. This action is likely to impair oedema resolution and to contribute to the pro-inflammatory actions of these prostaglandins.

SUBMITTER: Rehal S

PROVIDER: S-EPMC2807658 | biostudies-literature | 2009 Dec

REPOSITORIES: biostudies-literature

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Characterization of biosynthesis and modes of action of prostaglandin E2 and prostacyclin in guinea pig mesenteric lymphatic vessels.

Rehal Sonia S Blanckaert Pauline P Roizes Simon S von der Weid Pierre-Yves PY

British journal of pharmacology 20091201 8

<h4>Background and purpose</h4>Rhythmical transient constrictions of the lymphatic vessels provide the means for efficient lymph drainage and interstitial tissue fluid balance. This activity is critical during inflammation, to avoid or limit oedema resulting from increased vascular permeability, mediated by the release of various inflammatory mediators. In this study, we investigated the mechanisms by which prostaglandin E(2) (PGE(2)) and prostacyclin modulate lymphatic contractility in isolated ...[more]

PMID: 19922540

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Project description:In the current study, the potential contributions of ryanodine receptors (RyRs) to intrinsic pumping and responsiveness to substance P (SP) were investigated in isolated rat mesenteric collecting lymphatic vessels. Responses to SP were characterized in lymphatic vessels in the absence or presence of pretreatment with nifedipine to block L-type Ca2+ channels, caffeine to block normal release and uptake of Ca2+ from the sarcoplasmic reticulum, ryanodine to block all RyR isoforms, or dantrolene to more selectively block RyR1 and RyR3. RyR expression and localization in lymphatics was also assessed by quantitative PCR and immunofluorescence confocal microscopy. The results show that SP normally elicits a significant increase in contraction frequency and a decrease in end-diastolic diameter. In the presence of nifedipine, phasic contractions stop, yet subsequent SP treatment still elicits a strong tonic contraction. Caffeine treatment gradually relaxes lymphatics, causing a loss of phasic contractions, and prevents subsequent SP-induced tonic contraction. Ryanodine also gradually diminishes phasic contractions but without causing vessel relaxation and significantly inhibits the SP-induced tonic contraction. Dantrolene treatment did not significantly impair lymphatic contractions nor the response to SP. The mRNA for all RyR isoforms is detectable in isolated lymphatics. RyR2 and RyR3 proteins are found predominantly in the collecting lymphatic smooth muscle layer. Collectively, the data suggest that SP-induced tonic contraction requires both extracellular Ca2+ plus Ca2+ release from internal stores and that RyRs play a role in the normal contractions and responsiveness to SP of rat mesenteric collecting lymphatics.NEW & NOTEWORTHY The mechanisms that govern contractions of lymphatic vessels remain unclear. Tonic contraction of lymphatic vessels caused by substance P was blocked by caffeine, which prevents normal uptake and release of Ca2+ from internal stores, but not nifedipine, which blocks L-type channel-mediated Ca2+ entry. Ryanodine, which also disrupts normal sarcoplasmic reticulum Ca2+ release and reuptake, significantly inhibited substance P-induced tonic contraction. Ryanodine receptors 2 and 3 were detected within the smooth muscle layer of collecting lymphatic vessels.

Project description:Cough number and/or sound have been used to assess cough sensitivity/intensity and to discriminate cough patterns in clinical settings. However, to date, only manual counting of cough number in an offline manner is applied in animal cough studies, which diminishes the efficiency of cough identification and hinders the diagnostic discrimination of cough patterns, especially in animals with pulmonary diseases. This study aims to validate a novel recording/analysis system by which cough numbers are automatically counted and cough patterns are comprehensively differentiated in real time. The experiment was carried out in conscious guinea pigs exposed to aerosolized citric acid (CA, 150 mM) and prostaglandin E2 (PGE2, 0.43 mM). Animal body posture (video), respiratory flow, and cough acoustics (audio) were simultaneously monitored and recorded. Cough number was counted automatically, and cough sound parameters including waveform, duration, power spectral density, spectrogram, and intensity, were analyzed in real time. Our results showed that CA- and PGE2-evoked coughs had the same cough numbers but completely different patterns [individual coughs vs. bout(s) of coughs]. Compared to CA-evoked coughs, PGE2-evoked coughs possess a longer latency, higher cough rate (coughs/min), shorter cough sound duration, lower cough sound intensity, and distinct cough waveforms and spectrograms. A few mucus- and wheeze-like coughs were noted in response to CA but not to PGE2. In conclusion, our recording/analysis system is capable of automatically counting the cough number and successfully differentiating the cough pattern by using valuable cough sound indexes in real time. Our system enhances the objectivity, accuracy, and efficiency of cough identification and count, improves the intensity evaluation, and offers ability for pattern discrimination compared to traditional types of cough identification. Importantly, this approach is beneficial for assessing the efficacy of putative antitussive drugs in animals without or with pulmonary diseases, particularly in cases without significant change in cough number.

Project description:Study questionDoes the uterine vasculature play a localized role in promoting stromal cell decidualization in the human endometrium?Summary answerOur study demonstrated that hemodynamic forces induced secretion of specific endothelial cell-derived prostanoids that enhanced endometrial perivascular decidualization via a paracrine mechanism.What is known alreadyDifferentiation of stromal cell fibroblasts into the specialized decidua of the placenta is a progesterone-dependent process; however, histologically, it has long been noted that the first morphological signs of decidualization appear in the perivascular stroma. These observations suggest that the human endometrial vasculature plays an active role in promoting stromal differentiation.Study design, size, durationPrimary human endometrial stromal cells were co-cultured for 14 days with primary uterine microvascular endothelial cells within a microfluidic Organ-on-Chip model of the endometrium.Participants/materials, setting, methodsCultures were maintained with estradiol and a progestin, with or without continuous laminar perfusion to mimic hemodynamic forces derived from the blood flow. Some cultures additionally received exogenous agonist-mediated challenges. Decidualization in the microfluidic model was assessed morphologically and biochemically. ELISA was used to examine the culture effluent for expression of decidualization markers and prostaglandins. Immunofluorescence was used to monitor cyclooxygenase-2 expression in association with decidualization.Main results and the role of chanceA significantly enhanced stromal decidualization response was observed in the co-cultures when the endothelial cells were stimulated with hemodynamic forces (e.g. laminar shear stress) derived from controlled microfluidic perfusion (<0.001). Furthermore, the enhanced progestin-driven stromal differentiation was mediated via cyclooxygenase-2 and the paracrine action of prostaglandin E2 and prostacyclin. Altogether, these translational findings indicate that the vascular endothelium plays a key physiologic role during the early events of perivascular decidualization in the human endometrium.Large scale dataN/A.Limitations, reasons for cautionThis report is largely an in vitro study. Although we were able to experimentally mimic hemodynamic forces in our microfluidic model, we have not yet determined the contribution of additional cell types to the decidualization process or determined the precise physiological rates of shear stress that the microvasculature of the endometrium undergoes in vivo.Wider implications of the findingsIdentification of specific endothelial-derived prostaglandins and their role during endometrial reproductive processes may have clinical utility as therapeutic targets for reproductive disorders such as infertility, endometriosis, adenomyosis, pre-eclampsia and poor pregnancy outcomes.Study funding/competing interest(s)This work was supported by the Veterans Affairs (I01 BX002853), the Bill and Melinda Gates Foundation Grand Challenges Exploration (OPP1159411), the Environmental Toxicology Training Grant (NIH T32 ES007028) and the Environmental Protection Agency STAR Center Grant (83573601).Conflict of interestThe authors report no conflicts of interest.Trial registration numberN/A.

Project description:Hyperkalemia increases the organization of ventricular fibrillation (VF) and may also terminate it by mechanisms that remain unclear. We previously showed that the left-to-right heterogeneity of excitation and wave fragmentation present in fibrillating guinea pig hearts is mediated by chamber-specific outward conductance differences in the inward rectifier potassium current (I(K1)). We hypothesized that hyperkalemia-mediated depolarization of the reversal potential of I(K1) (E(K1)) would reduce excitability and thereby reduce VF excitation frequencies and left-to-right heterogeneity. We induced VF in Langendroff-perfused guinea pig hearts and increased the extracellular K(+) concentration ([K(+)](o)) from control (4 mM) to 7 mM (n = 5) or 10 mM (n = 7). Optical mapping enabled spatial characterization of excitation dominant frequencies (DFs) and wavebreaks, and identification of sustained rotors (>4 cycles). During VF, hyperkalemia reduced the maximum DF of the left ventricle (LV) from 31.5 +/- 4.7 Hz (control) to 23.0 +/- 4.7 Hz (7.0 mM) or 19.5 +/- 3.6 Hz (10.0 mM; p < 0.006), the left-to-right DF gradient from 14.7 +/- 3.6 Hz (control) to 4.4 +/- 1.3 Hz (7 mM) and 3.2 +/- 1.4 Hz (10 mM), the number of DF domains, and the incidence of wavebreak in the LV and interventricular regions. During 10 mM [K(+)](o), the rotation period and core area of sustained rotors in the LV increased, and VF often terminated. Two-dimensional computer simulations mimicking experimental VF predicted that clamping E(K1) to normokalemic values during simulated hyperkalemia prevented all of the hyperkalemia-induced VF changes. During hyperkalemia, despite the shortening of the action potential duration, depolarization of E(K1) increased refractoriness, leading to a slowing of VF, which effectively superseded the influence of I(K1) conductance differences on VF organization. This reduced the left-to-right excitation gradients and heterogeneous wavebreak formation. Overall, these results provide, to our knowledge, the first direct mechanistic insight into the organization and/or termination of VF by hyperkalemia.

Dataset Information

Characterization of biosynthesis and modes of action of prostaglandin E2 and prostacyclin in guinea pig mesenteric lymphatic vessels.

Publications

Characterization of biosynthesis and modes of action of prostaglandin E2 and prostacyclin in guinea pig mesenteric lymphatic vessels.

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