Diego Castanares-Zapatero

AMPK activation by glucagon-like peptide-1 prevents NADPH oxidase activation induced by hyperglycemia in adult cardiomyocytes

Exposure of cardiomyocytes to high glucose concentrations (HG) stimulates reactive oxygen species (ROS) production by NADPH oxidase (NOX2). NOX2 activation is triggered by enhanced glucose transport through a sodium-glucose cotransporter (SGLT) but not by a stimulation of glucose metabolism. The aim of this work was to identify potential therapeutic approaches to counteract this glucotoxicity. In cultured adult rat cardiomyocytes incubated with 21 mM glucose (HG), AMP-activated protein kinase (AMPK) activation by A769662 or phenformin nearly suppressed ROS production. Interestingly, glucagon-like peptide 1 (GLP-1), a new antidiabetic drug, concomitantly induced AMPK activation and prevented the HG-mediated ROS production (maximal effect at 100 nM). α2-AMPK, the major isoform expressed in cardiomyocytes (but not α1-AMPK), was activated in response to GLP-1. Anti-ROS properties of AMPK activators were not related to changes in glucose uptake or glycolysis. Using in situ proximity ligation assay, we demonstrated that AMPK activation prevented the HG-induced p47phox translocation to caveolae, whatever the AMPK activators used. NOX2 activation by either α-methyl-d-glucopyranoside, a glucose analog transported through SGLT, or angiotensin II was also counteracted by GLP-1. The crucial role of AMPK in limiting HG-mediated NOX2 activation was demonstrated by overexpressing a constitutively active form of α2-AMPK using adenoviral infection. This overexpression prevented NOX2 activation in response to HG, whereas GLP-1 lost its protective action in α2-AMPK-deficient mouse cardiomyocytes. Under HG, the GLP-1/AMPK pathway inhibited PKC-β2 phosphorylation, a key element mediating p47phox translocation. In conclusion, GLP-1 induces α2-AMPK activation and blocks HG-induced p47phox translocation to the plasma membrane, thereby preventing glucotoxicity.

Pharmacological treatment of delayed cerebral ischemia and vasospasm in subarachnoid hemorrhage.

Subarachnoid hemorrhage after the rupture of a cerebral aneurysm is the cause of 6% to 8% of all cerebrovascular accidents involving 10 of 100,000 people each year. Despite effective treatment of the aneurysm, delayed cerebral ischemia (DCI) is observed in 30% of patients, with a peak on the tenth day, resulting in significant infirmity and mortality. Cerebral vasospasm occurs in more than half of all patients and is recognized as the main cause of delayed cerebral ischemia after subarachnoid hemorrhage. Its treatment comprises hemodynamic management and endovascular procedures. To date, the only drug shown to be efficacious on both the incidence of vasospasm and poor outcome is nimodipine. Given its modest effects, new pharmacological treatments are being developed to prevent and treat DCI. We review the different drugs currently being tested.

Reduced scar maturation and contractility lead to exaggerated left ventricular dilation after myocardial infarction in mice lacking AMPKα1.

Cardiac fibroblasts (CF) are crucial in left ventricular (LV) healing and remodeling after myocardial infarction (MI). They are typically activated into myofibroblasts that express alpha-smooth muscle actin (α-SMA) microfilaments and contribute to the formation of contractile and mature collagen scars that minimize the adverse dilatation of infarcted areas. CF predominantly express the α1 catalytic subunit of AMP-activated protein kinase (AMPKα1), while AMPKα2 is the major catalytic isoform in cardiomyocytes. AMPKα2 is known to protect the heart by preserving the energy charge of cardiac myocytes during injury, but whether AMPKα1 interferes with maladaptative heart responses remains unexplored. In this study, we investigated the role of AMPKα1 in modulating LV dilatation and CF fibrosis during post-MI remodeling. AMPKα1 knockout (KO) and wild type (WT) mice were subjected to permanent ligation of the left anterior descending coronary artery. The absence of AMPKα1 was associated with increased CF proliferation in infarcted areas, while expression of the myodifferentiation marker α-SMA was decreased. Faulty maturation of myofibroblasts might derive from severe down-regulation of the non-canonical transforming growth factor-beta1/p38 mitogen-activated protein kinase (TGF-β1/p38 MAPK) pathway in KO infarcts. In addition, lysyl oxidase (LOX) protein expression was dramatically reduced in the scar of KO hearts. Although infarct size was similar in AMPK-KO and WT hearts subjected to MI, these changes resulted in compromised scar contractility, defective scar collagen maturation, and exacerbated adverse remodeling, as indicated by increased LV diastolic dimension 30days after MI. Our data genetically demonstrate the centrality of AMPKα1 in post-MI scar formation and highlight the specificity of this catalytic isoform in cardiac fibroblast/myofibroblast biology.

Connection between cardiac vascular permeability, myocardial edema, and inflammation during sepsis: role of the α1AMP-activated protein kinase isoform.

Objective:As adenosine monophosphate (AMP)-activated protein kinase both controls cytoskeleton organization in endothelial cells and exerts anti-inflammatory effects, we here postulated that it could influence vascular permeability and inflammation, thereby counteracting cardiac wall edema during sepsis. Design:Controlled animal study. Settings:University research laboratory. Subjects:C57BL/6J, &agr;1AMPK–/–, and &agr;1AMPK+/+ mice. Intervention:Sepsis was triggered in vivo using a sublethal injection of lipopolysaccharide (O55B5, 10 mg/kg), inducing systolic left ventricular dysfunction. Left ventricular function, edema, vascular permeability, and inflammation were assessed in vivo in both wild-type mice (&agr;1AMPK+/+) and &agr;1AMP-activated protein kinase–deficient mice (&agr;1AMPK–/–). The 5-aminoimidazole-4-carboxamide riboside served to study the impact of AMP-activated protein kinase activation on vascular permeability in vivo. The integrity of endothelial cell monolayers was also examined in vitro after lipopolysaccharide challenge in the presence of aminoimidazole-4-carboxamide riboside and/or after &agr;1AMP-activated protein kinase silencing. Measurements and Main Results:&agr;1AMP-activated protein kinase deficiency dramatically impaired tolerance to lipopolysaccharide challenge. Indeed, &agr;1AMPK–/– exhibited heightened cardiac vascular permeability after lipopolysaccharide challenge compared with &agr;1AMPK+/+. Consequently, an increase in left ventricular mass corresponding to exaggerated wall edema occurred in &agr;1AMPK–/–, without any further decrease in systolic function. Mechanistically, the lipopolysaccharide-induced &agr;1AMPK–/– cardiac phenotype could not be attributed to major changes in the systemic inflammatory response but was due to an increased disruption of interendothelial tight junctions. Accordingly, AMP-activated protein kinase activation by aminoimidazole-4-carboxamide riboside counteracted lipopolysaccharide-induced hyperpermeability in wild-type mice in vivo as well as in endothelial cells in vitro. This effect was associated with a potent protection of zonula occludens-1 linear border pattern in endothelial cells. Conclusions:Our results demonstrate for the first time the involvement of a signaling pathway in the control of left ventricular wall edema during sepsis. AMP-activated protein kinase exerts a protective action through the preservation of interendothelial tight junctions. Interestingly, exaggerated left ventricular wall edema was not coupled with aggravated systolic dysfunction. However, it could contribute to diastolic dysfunction in patients with sepsis.

The closure of arteriovenous fistula in kidney transplant recipients is associated with an acceleration of kidney function decline

Background The creation of arteriovenous fistula (AVF) may retard chronic kidney disease progression in the general population. Conversely, the impact of AVF closure on renal function in kidney transplant recipients (KTRs) remains unknown. Methods From 2007 to 2013, we retrospectively categorized 285 KTRs into three groups: no AVF (Group 0, n = 90), closed AVF (Group 1, n = 114) and left-open AVF (Group 2, n = 81). AVF closure occurred at 653 ± 441 days after kidney transplantation (KTx), with a thrombosis:ligation ratio of 19:95. Estimated glomerular filtration rate (eGFR) was determined using the Modification of Diet in Renal Disease equation. Linear mixed models calculated the slope and intercept of eGFR decline versus time, starting at 3 months post-KTx, with a median follow-up of 1807 days (95% confidence interval 1665–2028). Results The eGFR slope was less in Group 1 (−0.081 mL/min/month) compared with Group 0 (−0.183 mL/min/month; P = 0.03) or Group 2 (−0.164 mL/min/month; P = 0.09). Still, the eGFR slope significantly deteriorated after (−0.159 mL/min/month) versus before (0.038 mL/min/month) AVF closure (P = 0.03). Study periods before versus after AVF closure were balanced to a mean of 13.5 and 12.5 months, respectively, with at least 10 observations per patient (n = 99). Conclusions In conclusion, a significant acceleration of eGFR decline is observed over the 12 months following the closure of a functioning AVF in KTRs.

Reversible cardiac dysfunction after venlafaxine overdose and possible influence of genotype and metabolism.

Acute poisoning by large venlafaxine (VEN) overdoses may result in serious cardiac events like acute left ventricular dysfunction or even fatalities. In humans, venlafaxine is biotransformed for the most part by CYP2D6 and CYP2C19 isoenzymes to its major metabolite O-desmethylvenlafaxine (ODV), and in parallel to N-desmethylvenlafaxine (NDV) and N,O-didesmethylvenlafaxine (NODV) by several CYP isoenzymes, mainly including CYP3A4 and CYP2C19. The ODV concentrations must be taken into consideration along with those of VEN when relating blood concentrations to clinical effects. Herein we describe a case of reversible cardiac dysfunction following VEN self-poisoning. The peak ODV concentration (46,094ng/mL) was observed 20h post-ingestion, being one of the highest ever associated with survival. The calculated elimination half-life was 10h for VEN and 22h for ODV, and the calculated ODV/VEN metabolic ratio 12.9. Genotyping confirmed the patient to have an extensive metabolizer phenotype for CYP2D6, and an ultra-rapid metabolizer phenotype for CYP2C19. We suspect cardiotoxicity was related to sustained ODV exposure despite extensive VEN metabolism, and therefore suggest that ODV metabolism saturation may occur following large VEN overdoses.

Acute ventricular wall thickening: sepsis, thrombotic microangiopathy, or myocarditis?

Background. Acute myocardial oedema has been documented in experimental models of ischemia-reperfusion injury or sepsis and is usually investigated by magnetic resonance imaging. Purpose. We describe a case of acute ventricular wall thickening documented by echocardiography in a patient developing sepsis and thrombotic microangiopathy. Case Description. A 40-year-old woman, with a history of mixed connective tissue disease, was admitted with laryngeal oedema and fever. She developed Streptococcus pneumoniae septicaemia and subsequent laboratory abnormalities were consistent with a thrombotic microangiopathy. Echocardiography revealed an impressive diffuse thickening of the whole myocardium (interventricular septum 18 mm; posterior wall 16 mm) with diffuse hypokinesia and markedly reduced left ventricular ejection fraction (31%). There was also a moderate pericardial effusion. Echocardiography was normal two months before. The patient died from acute heart failure. Macroscopic and microscopic examination of the heart suggested that the ventricular wall thickening was induced by oedematous changes, together with an excess of inflammatory cells. Conclusion. Acute ventricular wall thickening that corresponded to myocardial oedema as a first hypothesis was observed at echocardiography during the course of septicaemia complicated by thrombotic microangiopathy.

Prone positioning induced hepatic necrosis after liver transplantation

A 19-year-old woman developed severe pneumonia with ARDS 7 days after a liver transplant. Hypoxemia gradually worsened despite maximal respiratory management and she was turned to the prone position (PP) for 16 h. During PP, oxygenation dramatically improved. PEEP was slightly increased from 9 to 10 cmH2O and maximal inspiratory pressure decreased from 36 to 27 cmH2O. Doses of norepinephrine (0.11 mcg/kg/min) were unaffected and pH and lactate levels remained in normal ranges. Next, routine laboratory tests showed an unexpected increase in serum liver enzymes (AST from 84 to 1,934 IU/l; ALT from 234 to 1,538 IU/l). Liver vascular flows assessed by Doppler ultrasonography were normal. An abdominal computed tomography showed extensive necrosis of the anteromedian part of the liver, which did not correspond to a specific vascular territory (Fig. 1). Topography of the ischemic lesions raises the hypothesis of a link between direct compression during PP and the necrosis. No sign of liver failure occurred and transaminase levels rapidly normalized. The patient’s condition gradually improved allowing extubation and discharge from ICU 28 days later. Prone positioning improves oxygenation in ARDS; however, clinicians should be aware of the potential risk of liver ischemia in liver transplant recipients.

The Case ∣ Multiple-organ failure in a dialysis patient with pericarditis

A 61-year-old man was admitted to the intensive care unit for hypotension and confusion. Hemodialysis was restarted 2 months before because of chronic allograft nephropathy, after 24 years of kidney transplantation for IgA nephropathy. At dialysis initiation, a discrete pericardial effusion was noted. Despite daily dialysis, dry-weight reduction, and reduced anticoagulation, effusion increased and slightly impaired right ventricle function. Pericardocentesis was delayed as colchicine 0.5 mg daily rapidly allowed pain relief and improvement of pericarditis; non-steroidal anti-inflammatory drugs were not associated because of active gastric ulcers. Other long-term medications included cyclosporin (100 mg b.i.d., target trough level ~60 ng/ml), prednisolone (2 mg o.d.), and rosuvastatin (10 mg o.d.). As chest pain recurred 12 days later, colchicine dose was increased to 1 mg o.d. After 7 days without any side effects, the patient suddenly developed diarrhea, confusion, and hypotension. Laboratory results are shown in Table 1. Multiple-organ failure soon developed, with leucopenia, acute liver failure, and rhabdomyolysis. Vasopressors, mechanical ventilation, and continuous veno-venous hemofiltration were initiated. Echocardiography showed a reduced pericardial effusion and no cardiac dysfunction. Bacteriological and imaging studies did not point to any infection. Mesenteric ischemia was suspected, but exploratory laparotomy did not show bowel necrosis. The patient died 36 h after admission from refractory shock. Post-mortem examination was performed.

Interaction between tacrolimus and clindamycin

Sir, Tacrolimus is widely used in organ transplantation to prevent allograft rejection. Its hepatic metabolism via cytochrome P450 (CYP) 3A4 represents the major eliminating process. In addition, its bioavailability depends on intestinal P-glycoproteins (PGP) and CYP3A5 activities. Due to its potential toxicity, tacrolimus usage requires a close drug monitoring, as well as the early identification of any pharmacological interaction. Here, we report on a novel interaction between tacrolimus and clindamycin in a renal transplant recipient with Pneumocystis jirovecii pneumonia (PJP). A 61-year-old woman underwent kidney transplantation from a deceased donor for end-stage renal disease secondary to chronic glomerulonephritis with IgA deposits. Two months later, she presented with grade IV dyspnoea. Maintenance immunosuppression included modified-release (MR) tacrolimus 15 mg/day, mycophenolate mofetil (MMF) 720 mg/day and prednisolone 4 mg/day. Thorax computed tomography showed bilateral ground-glass opacities compatible with PJP, as confirmed by bronchoalveolar lavage analyses. MMF was interrupted, and sulphamethoxazole–trimethoprim (4 × 1280 mg/day) was initiated with methylprednisolone (32 mg/day). The patients condition declined, requiring mechanical ventilation. From that time, medications were given through a nasogastric tube, and tacrolimus trough level remained stable ∼10 ng/mL while receiving 7 mg/day (Figure 1). Because sulphamethoxazole–trimethoprim treatment induced type IV renal tubular acidosis, antimicrobial therapy was substituted for atovaquone (1500 mg/day) and clindamycin (2400 mg/day IV) on Day 8. Tacrolimus trough level progressively decreased, while its dosage was accordingly increased (Figure 1). Six days later, both atovaquone and clindamycin were interrupted with a progressive return of tacrolimus trough level to baseline. Since the administration of MR tacrolimus through a nasogastric tube may decrease its disposition, the twice-a-day form was initiated (Figure 1). Fibroscopy was performed 10 days after antibiotic withdrawal and disclosed PJP recurrence. Both atovaquone and clindamycin were resumed for 6 days. Again, tacrolimus trough level significantly decreased (Figure 1) though no other medication was initiated. Renal graft function remained stable. Fig. 1 Changes in tacrolimus blood trough level (nanogram per millilitre) and tacrolimus dose (milligram per day) according to atovaquone/clindamycin therapy from Day 4 at the intensive care unit. Advagraf® and Prograft® represent the modified-release ... Because of its extensive metabolism, tacrolimus disposition tightly depends on CYP3A4/5 and PGP activities. Here, a significant decrease of tacrolimus trough level was repeatedly observed when co-administered with atovaquone and clindamycin. Atovaquone is 94% excreted unchanged in faeces, with a modest inhibition of CYP2C19 which is not implicated in tacrolimus metabolism [1]. Conversely, clindamycin metabolism primarily requires its oxidation by CYP3A4/5 and exhibits a clear propensity to induce CYP3A4 activity [2,3]. Thus, similarly to former cases reported under cyclosporine [4], clindamycin may accelerate tacrolimus catabolism. Here, the co-administration of clindamycin and tacrolimus led twice to a significant decrease in tacrolimus trough level. Such temporal relationship is highly suggestive of pharmacological interactions, as supported by a significant Drug Interaction Probability Scale (DIPS) score [5]. In conclusion, the present observation emphasizes the need for a close monitoring of tacrolimus trough level when co-administered with high-dose clindamycin. Conflict of interest statement. None declared.