Uncovering the dominant role of root metabolism in shaping rhizosphere metabolome under drought in tropical rainforest plants

Plant-soil-microbe interactions are crucial for driving rhizosphere processes that contribute to metabolite turnover and nutrient cycling. With the increasing frequency and severity of water scarcity due to climate warming, understanding how plant-mediated processes, such as root exudation, influence soil organic matter turnover in the rhizosphere is essential. In this study, we used 16S rRNA gene amplicon sequencing, rhizosphere metabolomics, and position-specific 13C-pyruvate labeling to examine the effects of three different plant species (Piper auritum, Hibiscus rosa sinensis, and Clitoria fairchildiana) and their associated microbial communities on soil organic carbon turnover in the rhizosphere. Our findings indicate that in these tropical plants, the rhizosphere metabolome is primarily shaped by the response of roots to drought rather than direct shifts in the rhizosphere bacterial community composition. Specifically, the reduced exudation of plant roots had a notable effect on the metabolome of the rhizosphere of P. auritum, with less reliance on neighboring microbes. Contrary to P. auritum, H. rosa sinensis and C. fairchildiana experienced changes in their exudate composition during drought, causing alterations to the bacterial communities in the rhizosphere. This, in turn, had a collective impact on the rhizosphere's metabolome. Furthermore, the exclusion of phylogenetically distant microbes from the rhizosphere led to shifts in its metabolome. Additionally, C. fairchildiana appeared to be associated with only a subset of symbiotic bacteria under drought conditions. These results indicate that plant species-specific microbial interactions systematically change with the root metabolome. As roots respond to drought, their associated microbial communities adapt, potentially reinforcing the drought tolerance strategies of plant roots. These findings have significant implications for maintaining plant health and preference during drought stress and improving plant performance under climate change.

[Succès de traitement par Cabergoline d'une série de cas de cardiomyopathie du péripartum, incluant un cas critique nécessitant une assistance circulatoire mécanique]

Peripartum cardiomyopathy is a life-threatening condition that requires urgent diagnosis and management. Bromocriptine was established as disease specific therapy; less data is known about Cabergolin which is another prolactin secretion inhibitor. In this paper we report 4 peripartum cardiomyopathy cases treated successfully with Cabergoline, including a cardiogenic shock case requiring mechanical circulatory support.

Microbial sensitivity to temperature and sulfate deposition modulates greenhouse gas emissions from peat soils

Peatlands are among the largest natural sources of atmospheric methane (CH₄ ) worldwide. Microbial processes play a key role in regulating CH₄ emissions from peatland ecosystems, yet the complex interplay between soil substrates and microbial communities in controlling CH₄ emissions as a function of global change remains unclear. Herein, we performed an integrated analysis of multi-omics data sets to provide a comprehensive understanding of the molecular processes driving changes in greenhouse gas (GHG) emissions in peatland ecosystems with increasing temperature and sulfate deposition in a laboratory incubation study. We sought to first investigate how increasing temperatures (4, 21, and 35°C) impact soil microbiome-metabolome interactions; then explore the competition between methanogens and sulfate-reducing bacteria (SRBs) with increasing sulfate concentrations at the optimum temperature for methanogenesis. Our results revealed that peat soil organic matter degradation, mediated by biotic and potentially abiotic processes, is the main driver of the increase in CO₂ production with temperature. In contrast, the decrease in CH₄ production at 35°C was linked to the absence of syntrophic communities and the potential inhibitory effect of phenols on methanogens. Elevated temperatures further induced the microbial communities to develop high growth yield and stress tolerator trait-based strategies leading to a shift in their composition and function. On the other hand, SRBs were able to outcompete methanogens in the presence of non-limiting sulfate concentrations at 21°C, thereby reducing CH₄ emissions. At higher sulfate concentrations, however, the prevalence of communities capable of producing sufficient low-molecular-weight carbon substrates for the coexistence of SRBs and methanogens was translated into elevated CH₄ emissions. The use of omics in this study enhanced our understanding of the structure and interactions among microbes with the abiotic components of the system that can be useful for mitigating GHG emissions from peatland ecosystems in the face of global change.

Comparative study between supported bimetallic catalysts for nitrate remediation in water

As the population grows and the demand for water rises, the development of efficient and sustainable water purification techniques is becoming increasingly important to ensure access to clean and safe water in the future. The pollution of surface and groundwater by nitrate ( NO 3 − {\text{NO}}_{3}^{-} ) is a growing global concern due to the rise in nitrogen-rich waste released from agriculture and industry. The removal of nitrate ions from aqueous media using bimetallic catalysts loaded on several supports was studied. Multiwalled carbon nanotubes, activated carbon, titanium dioxide, titanium dioxide/multiwalled carbon nanotubes, and Santa Barbara Amorphous-15 were used as supports to synthesize these bimetallic catalysts. The effects of the support type, supported metal, and catalyst reduction method on the nitrate reduction activity in water were investigated. The catalysts were characterized by X-ray diffraction, fourier-transform infrared spectroscopy, Brunauer-Emmett-Teller isotherm, inductively coupled plasma spectroscopy, and field emission gun scanning transmission electron microscope. In terms of nitrate conversion, high-temperature hydrogen reduction of the catalysts was a more effective method of catalyst preparation than NaBH4 reduction. Except for the carbon nanotube-TiO2 composite, pH fixation using CO2 flow improved the efficiency of supported catalysts. The catalysts 1Pd–1Cu/TiO2 and 1Pd–Cu/SBA-15 presented the highest catalytic activity, but the latter was the most selective to nitrogen.

The Lebanese left ventricular assist device experience, a success story despite the odds

BACKGROUND AND AIM

Heart failure is still a leading cause of mortality and morbidity. Assist devices are reserved for advanced heart failure patients with no other therapeutic options. We aim in this paper to describe the characteristics and outcome of Lebanese left ventricular assist device (LVAD) patients.

RESULTS

From 2010 till December 2019, 78 patients were implanted with assist devices at the Beirut cardiac Institute, 82 pumps were used. To the most recent follow up after 10 years, 26 patients died (34%). 24 patients of 35 (68%) survived more than 5 years. Seven patients only (9%) died during one month of surgery. One year mortality was 19% (15 patients). The leading cause of early mortality was infection, whereas cerebrovascular accidents CVA were the leading cause of late mortality. Pump thrombosis occurred in 12% of the cases. The most serious long term complication was haemorrhagic CVA. Only seven patients (9%) received heart transplantation, with a mean time on support prior to transplantation of 1303 ± 213 days.

CONCLUSION

In this manuscript we reported the characteristics and outcome of the largest population of LVAD patients in Lebanon. The survival rate was 81% at one year. These findings were comparable to the international registries except for rates of heart transplantation. More efforts should be made to encourage organ donation in Lebanon.

Right ventricle failure in patients treated with left ventricular assist device

This review article aim to highlight the right ventricular function peri left ventricular assist device implantation, and to assess the incidence, physiopathology, predictors, management and prognosis, of right ventricular failure post-implant.

Tropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance

Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 °C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats.

Abstract P3-07-11: Inhibition of Pin1 or CDK-mediated Smad3 phosphorylation reduces triple negative breast cancer cell EMT, migration and invasion

Introduction: Triple negative breast cancer (TNBC) is an aggressive subtype associated with poor outcomes. Accordingly, there is an urgent need to develop novel and targeted therapeutics for patients with this disease subtype. Cyclins D and E and the corresponding activation of CDK4/2 represent promising therapeutic targets for the treatment of TNBC. CDK4/2 can non-canonically phosphorylate Smad3, a key TGFβ signaling intermediate, and this phosphorylation is associated with the promotion of cell migration and EMT in cyclin-overexpressing breast cancers. Additionally, CDK-mediated Smad3 phosphorylation facilitates an interaction between Smad3 and Pin1. Pin1 is a cis-trans isomerase that is also overexpressed in aggressive breast cancers and can enable TNBC cell migration. Based on these findings, we hypothesized that blockade of the CDK-mediated Smad3-Pin1 interaction, either through inhibition of Pin1 or CDK-mediated Smad3 phosphorylation, would abrogate TNBC cell migration and invasion.

Methods: Pin1 expression was knocked-down (KD) in MDA-MB-231, MDA-MB-436, and Hs578T TNBC cells by transfection with Pin1-targeting siRNA (siPin1) or control non-specific siRNA (siNS). KD efficiency was confirmed with immunoblotting. Pin KD/TNBC cell migration and invasion assays were performed on uncoated or Matrigel-coated trans-wells, respectively. Media containing 10% FBS was used as a chemoattractant. Following Pin1 KD, immunoblotting was used to evaluate EMT-associated protein expression. To inhibit CDK-mediated Smad3 phosphorylation, TNBC cells were treated with 600 nM of CDK2 inhibitor (CDK2i) for 72 hours. Immunoblotting was then performed to determine Smad3 phosphorylation and EMT-associated protein expression. Co-immunoprecipitation assays were used to examine the impact of CDK2i treatment on the Smad3-Pin1 interaction. Finally, following CDK2i treatment, assays were performed to determine the ability of TNBC cells to migrate and invade.

Results: KD of Pin1 expression in TNBC cells resulted in a decrease in cell migration and invasion when compared to control cells in all the study cell lines. This corresponded with changes in EMT-associated protein expression, including increased levels of ZO-1 and claudin and decreased β-catenin. CDK2i treatment produced a decrease in Smad3 T179 site non-canonical phosphorylation and inhibited Smad3-Pin1 binding. CDK2i treatment also abrogated TNBC cell migration and invasion, paralleling expression changes in EMT-associated proteins with an increase in claudin and decrease in β-catenin.

Conclusions: Inhibition of the Smad3-Pin1 interaction, through KD of Pin1 expression or CDK2i-mediated blockade of non-canonical Smad3 phosphorylation, reduced TNBC cell EMT-type changes, demonstrated by increased expression of the tight junction proteins ZO-1 and claudin and decreased β-catenin, a key player in the WNT pathway. These findings also correlated to a reduction in TNBC cell migration and invasion. Collectively, these data show that the Smad3-Pin1 interaction, facilitated by CDK-mediated Smad3 phosphorylation, is associated with pro-migratory TGFβ signaling. Inhibition of this interaction, with CDK2 inhibitor treatment, may provide an important therapeutic option for TNBC patients.

Citation Format: Thomas AL, Hamdan R, Hong A, Lind H, Oppat K, Rosenthal E, Thomas AJ, Jeruss JS. Inhibition of Pin1 or CDK-mediated Smad3 phosphorylation reduces triple negative breast cancer cell EMT, migration and invasion [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-07-11.

Abstract P5-04-13: Pin1 negatively impacts Smad3 tumor suppression in triple negative breast cancer cell lines

Introduction: Triple negative breast cancer (TNBC) is an aggressive subtype associated with poor outcomes. Accordingly, there is an urgent need to develop novel and targeted therapeutics for patients with this disease subtype. Cyclins D and E and the corresponding activation of CDK4/2 represent promising therapeutic targets for the treatment of TNBC. CDK4/2 can non-canonically phosphorylate Smad3, a key TGFβ signaling intermediate, to promote the transition from tumor suppressive to oncogenic TGFβ activity in cyclin-overexpressing breast cancers. We identified a Smad3 interaction with Pin1, a cis-trans isomerase also overexpressed in aggressive breast cancers and associated with CDK-mediated Smad3 phosphorylation. Smad3 interaction with Pin1 can influence protein function and fidelity through recruitment of Smurf2 and subsequent proteasomal degradation. Based on these findings, we hypothesized that inhibition of the CDK-mediated Smad3-Pin1 interaction would stabilize Smad3 protein expression and restore tumor-suppressive Smad3 activity.

Methods: Pin1 expression was knocked-down (KD) in MDA-MB-231 TNBC cells by transfecting with Pin1-targeting siRNA (siPin1) or control non-specific siRNA (siNS). KD efficiency was confirmed by immunoblotting. To assay Smad3 transcriptional activity with Pin1 KD, luciferase reporter studies were performed. Also, following Pin1 KD, immunoblotting was used to determine expression of Smad3 and associated protein targets. MTS assays were utilized to determine cellular proliferation after Pin1 KD. Transwell migration assays were used to assay the effect of Pin1 KD or CDK2 inhibitor treatment, which blocked non-canonical Smad3 Thr179 phosphorylation, on TNBC cell migration.

Results: KD of Pin1 expression in TNBC cell lines resulted in an increase in Smad3 transcriptional activity compared to control cells, and correlated with an increase in expression of cdki p15 and a decrease in c-myc, Smad3-target genes and cell cycle regulators. Additionally, Pin1 KD resulted in a significant decrease in TNBC cell proliferation compared to siNS control TNBC cells. Smad3 protein levels increased following Pin1 KD, suggesting Pin1 action may negatively impact Smad3 stability. We also found that KD of Pin1 or treatment with a CDK2 inhibitor, which blocked Smad3 noncanonical Thr179 phosphorylation, resulted in significantly reduced TNBC cell migration.

Conclusions: Inhibiting the Smad3-Pin1 interaction by knock-down of Pin1 expression in TNBC cells restored Smad3 transcriptional activity, which correlated to an increase in expression of the Smad3 associated protein cdki p15, decrease in c-myc, and a decrease in cellular proliferation. Additionally, Pin1 KD enhanced Smad3 protein levels, suggesting a role of Pin1 in mediating Smad3 stability. Inhibiting the Smad3-Pin1 interaction with Pin1 KD or CDK2 inhibitor treatment also reduced TNBC cell migration. Collectively, these data suggest that the Smad3-Pin1 interaction, facilitated by noncanonical CDK-mediated Smad3 phosphorylation, is associated with pro-tumorigenic and pro-migratory TGFβ signaling, and inhibition of this interaction may provide an important therapeutic option for TNBC patients.

Citation Format: Thomas AL, Hamdan R, Hong A, Rosenthal E, Thomas AJ, Jeruss JS. Pin1 negatively impacts Smad3 tumor suppression in triple negative breast cancer cell lines. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-04-13.

Abstract P5-11-01: Impact of CDK mediated Smad3 phosphorylation and Pin1 in triple negative breast cancer cell migration

Introduction: Estrogen receptor (ER), progesterone receptor (PR), and Human Epidermal Growth Factor Receptor 2 (HER2) negative breast cancers, also known as triple negative breast cancers can overexpress cyclins, such as cyclin D and E, which have been linked to cancer progression and metastasis. Cyclin/CDK complexes can phosphorylate and regulate Smads, downstream signaling proteins in the transforming growth factor-beta (TGF-b) superfamily. CDKs phosphorylate Smad3, predominantly in the linker region, resulting in the decreased tumor suppressive role of this protein. The peptidyl-prolyl cis/trans isomerase Pin1 is also overexpressed in breast cancer. Pin1 can bind phosphorylated Smads contributing to TGF-β induced cell migration and invasion. Inhibition of CDK-mediated Smad3 phosphorylation has been shown to restore Smad3 activity and decrease tumor cell migration in vitro. Based on these findings, we hypothesized that inhibition of Pin1 or CDK-mediated Smad3 phosphorylation would result in decreased triple negative breast cancer cell migration.

Methods: Hs578T, MDA-MB-436, and MDA-MB-231 triple negative breast cancer cells (TN) were transfected with either an si control (siCN) or an siPin1 plasmid to knockdown Pin1 protein expression. Transwell migration assays were used to determine the effect of Pin1 knockdown on migration. TN cells were treated with CDK4 or CDK2 inhibitors alone or in combination. The study cells were also stably transduced with lentiviral empty vector, wild-type (WT) Smad3, or a Smad3 mutant (5M) resistant to CDK-mediated phosphorylation. The effect of pharmacologically or genetically inhibiting CDK-mediated Smad3 phosphorylation on Pin1 binding to phosphorylated Smad3 (p-Smad3) or total Smad3 was determined using a co-immunoprecipitation assay (Co-IP).

Results: Transfecting the study cells with siPin1 resulted in decreased cell migration when compared to the siCN transfected cells. Treatment with the CDK4 or CDK2 inhibitors alone or in combination did not affect Pin1 protein levels, but resulted in decreased Pin1 binding to p-Smad3 with the greatest decrease found after treatment with combination therapy. Similarly, transduction of the study cells with the WT or the 5M Smad3 constructs had no effect on Pin1 levels but resulted in decreased Pin1 binding to Smad3. The greatest decrease was observed in the 5M transduced cells.

Concusions: Inhibition of CDK-mediated Smad3 phosphorylation and knock down of Pin1 resulted in decreased migration of TN breast cancer cells. Inhibition of CDK-mediated Smad3 phosphorylation by mutation of the CDK phosphorylation sites or by treatment with CDK4 and CDK2 inhibitors negatively impacted Pin1 binding to Smad3. Together, these findings indicate that CDK-mediated Smad3 phosphorylation enhances Pin1 binding to Smad3 and promotes tumor cell migration in triple negative breast cancer cells.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-11-01.

Abstract P6-04-12: CDK inhibition mediates tumor suppressive Smad3 action and decreased metastatic phenotypes in triple negative breast cancer cells

Introduction: Breast cancer onset and disease progression has been linked to members of the TGFb superfamily and their downstream signaling components, the Smads. Changes in Smad signaling have been associated with the dichotomous role of TGFβ in malignancy, mediating both tumor suppressant and tumor promoting behaviors in breast cancer. Our previous work showed that cyclin/CDK mediated phosphorylation of Smad3 resulted in the inhibition of canonical tumor suppressant Smad3 action. We thus hypothesized that activation of CDKs leads to phosphorylation and inhibition of Smad3, releasing cell cycle arrest and promoting cell proliferation and metastasis. Using triple negative breast cancer cell lines, we examined the impact of specific CDK inhibitors (CDKis) on signaling patterns, metastatic phenotypes, and protein expression profiles.

Methods: Triple negative cell lines Hs578T, MDA-MB-231 and MDA-MB-436 were treated with CDK2i or CDK4i and Smad3 activity was measured using a luciferase assay. Transwell migration and Matrigel invasion assays were used to show the effect of transfection with Smad3 CDK phosphorylation site mutants, resistant to inhibitory CDK phosphorylation, or treatment with CDK2i or CDK4i on the study cells. Immunoblotting was performed to measure protein expression levels of Smad3, pSmad3 T179, and MMP2. A novel live cell array was implemented to quantify changes in activity of 14 cancer-related transcription factors over a period of 3 days. TUNEL and Ki67 staining analysis and a xenograft mouse model were used to determine impact of CDKis, in combination with paclitaxel chemotherapy, on apoptosis and tumor growth respectively.

Results: Treatment of study cells with CDK2i or CDK4i resulted in increased Smad3 activity and decreased migration and invasion in the study cells. Transfection with a 5M Smad3 mutant construct, containing mutations in all 5 CDK phosphorylation sites, resulted in the greatest decrease in cell migration, when compared with cells transfected with both vector control or WT Smad3. CDK2i or CDK4i therapy resulted in decreased Smad3 protein phosphorylation at the T179 site, while total Smad3 levels were unaffected. CDK2i/4i treatment also resulted in decreased MMP2 expression. The array studies revealed decreased activity of EMT transcription factors B-catenin, Snail, Twist, in MDA-MB-231 cells following CDK2i treatment. CDK2i and paclitaxel combination treatment resulted in increased apoptosis and decreased tumor volume and Ki67 staining compared to control treatment.

Conclusions: We have shown for the first time that cyclin/CDK activity, in part, mediates the metastasis-associated role of Smad3 in triple negative breast cancer cells. Importantly, both CDK2i and CDK4i treatment resulted in decreased cell migration/invasion and also corresponded to decreased MMP2 expression. Lastly, the array studies revealed CDK2i mediated effects on key transcription factors associated with the promotion of EMT. Future studies will explore the significance of Smad3 interaction with these EMT factors and will pursue the clinical application of CDK2i for patients with triple negative/cyclin overexpressing breast cancer.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-04-12.

Linking phosphorus sequestration to carbon humification in wetland soils by 31P and 13C NMR spectroscopy

Phosphorus sequestration in wetland soils is a prerequisite for long-term maintenance of water quality in downstream aquatic systems, but can be compromised if phosphorus is released following changes in nutrient status or hydrological regimen. The association of phosphorus with relatively refractory natural organic matter (e.g., humic substances) might protect soil phosphorus from such changes. Here we used hydrofluoric acid (HF) pretreatment to remove phosphorus associated with metals or anionic sorption sites, allowing us to isolate a pool of phosphorus associated with the soil organic fraction. Solution (31)P and solid state (13)C NMR spectra for wetland soils were acquired before and after hydrofluoric acid pretreatment to assess quantitatively and qualitatively the changes in phosphorus and carbon functional groups. Organic phosphorus was largely unaffected by HF treatment in soils dominated by refractory alkyl and aromatic carbon groups, indicating association of organic phosphorus with stable, humified soil organic matter. Conversely, a considerable decrease in organic phosphorus following HF pretreatment was detected in soils where O-alkyl groups represented the major fraction of the soil carbon. These correlations suggest that HF treatment can be used as a method to distinguish phosphorus fractions that are bound to the inorganic soil components from those fractions that are stabilized by incorporation into soil organic matter.

The effect of aerated rock filter geometry on the rate of nitrogen removal from facultative pond effluents

Rock filters are an established technology for polishing waste stabilization pond effluents. However, they rapidly become anoxic and consequently do not remove ammonium-nitrogen. Horizontal-flow aerated rock filters (HFARF), developed to permit nitrification and hence ammonium-N removal, were compared with a novel vertical-flow aerated rock filter (VFARF). There were no differences in the removals of BOD5, TSS and TKN, but the VFARF consistently produced effluents with lower ammonium-N concentrations (<0.3 mg N/L) than the HFARF (0.8-1.5 mg N/L) and higher nitrate-N concentrations (24-29 mg N/L vs. 17-24 mg N/L).

[Cerebral aneurysm and subarachnoid hemorrhage revealed by a Tako Tsubo syndrome]

Cerebral hemorrhage is usually associated to many cardiac disorders, mimicking acute coronary syndrome. We relate a case of a postmenopausal woman presenting at emergency room for acute coronary syndrome and whose evaluation revealed a subarachnoidal hemorrhage, normal coronary arteries, and a typical Tako Tsubo aspect on echocardiography with apical ballooning and hyperkinesis with basal hypokinesis.

[Heart rate variability alteration in patients on chronic hemodialysis]

BACKGROUND AND AIM

Decrease in heart rate variability (HRV) is a known risk factor for cardiovascular morbidity and mortality. The aim of our study is to evaluate HRV in chronic hemodialysis patients and to determine factors that might decrease or increase it.

METHODS

This is a retrospective study including 51 patients, 23 males and 28 females, with a mean of age of 64.5 years (23-84 years) on chronic hemodialysis for end stage renal disease due to various causes. Twenty-four-hour heart rate monitoring was recorded in all patients to evaluate HRV. HRV of hemodialysis patients was compared to normal patients (control). We also looked for correlation between HRV and a number of clinical and biological factors.

RESULTS

All HRV parameters were decreased in chronic hemodialysis patients compared to normal controls with a significant difference (p<0.0005). HRV decreases with age (p=0.012), and is lower in diabetic patients (p=0.026). Interestingly, we found that chronic hemodialysis patients on beta-blockers had higher HRV with p=0.011.

CONCLUSION

HRV is reduced in chronic hemodialysis patients mainly in old and diabetic patients, but this decrease is less important in those receiving beta-blockers.

[Beneficial effect of sildenafil following surgery for mitral stenosis complicated by pre-capillary pulmonary hypertension: report of two cases]

Pulmonary hypertension is a serious disorder, difficult to treat especially in the severe forms. The treatment consists mainly of calcium channel blockers, anti-coagulation, intravenous epoprostenol, inhaled nitric oxide and recent agents as bosentan and sildenafil. Sildenafil, a phosphodiesterase 5 specific inhibitor, has been largely evaluated in primary pulmonary hypertension, and in some cases of secondary pulmonary hypertension including parenchymal and thromboembolic diseases; it has not yet been evaluated in severe pulmonary hypertension with elevated pre-capillary resistance in operated mitral stenosis. We report the cases of two patients operated from mitral valve replacement for severe mitral stenosis with elevated pre-capillary resistance, where oral sildenafil, introduced empirically immediately after the surgical procedure at the dose of 50 mg/d, permitted a significant decrease in pulmonary pressures and resistances, allowing a rapid withdrawal of nitric oxide and reducing therefore hospitalization time in the intensive care unit. We think that this simple treatment, with or without association to nitric oxide, should be generalized to persistent pulmonary hypertension following cardiac surgery.