Evaluación terapéutica del bevacizumab, intravítreo, en el tratamiento del edema macular diabético difuso.

Tesis (Doctor en Medicina) UANL, 2011.

Cerebral edema and acute liver failure : pathophysiological mechanisms and new therapeutic approaches

L’encéphalopathie hépatique (EH) se développe chez les patients atteints d’une maladie du foie et se caractérise par de nombreuses anomalies neuropsychiatriques. L’insuffisance hépatique aiguë (IHA) se caractérise par une perte progressive de l’état de conscience, par une augmentation rapide de l’œdème cérébral et une augmentation de la pression intracrânienne entraînant une herniation cérébrale et la mort. Plusieurs facteurs sont responsables du développement de l’EH mais depuis une centaine d’années, l’hyperammonémie qui peut atteindre des concentrations de l’ordre de plusieurs millimolaires chez les patients atteints d’IHA aux stades de coma est considérée comme un facteur crucial dans la pathogenèse de l’EH. La présente thèse comprend 4 articles suggérant l’implication de nouveaux mécanismes pathogéniques dans le développement de l’EH et de l’œdème cérébral associés à l’IHA et tente d’expliquer l’effet thérapeutique de l’hypothermie et de la minocycline dans la prévention de l’EH et de l’œdème cérébral: 1. L’IHA induite par dévascularisation hépatique chez le rat se caractérise par une augmentation de la production de cytokines pro-inflammatoires cérébrales (IL-6, IL-1, TNF-). Cette observation constitue la première évidence directe que des mécanismes neuro-inflammatoires jouent une rôle dans la pathogenèse de l’EH et de l’œdème cérébral associés à l’IHA (Chapitre 2.1, articles 1 et 2). 2. L’activation de la microglie telle que mesurée par l’expression de marqueurs spécifiques (OX42, OX-6) coïncide avec le développement de l’encéphalopathie (stade coma) et de l’œdème cérébral et s’accompagne d’une production accrue de cytokines pro-inflammatoires cérébrales (Chapitre 2.1, article 1 et 2). 3. Un stress oxydatif/nitrosatif causé par une augmentation de l’expression de l’oxyde nitrique synthétase et une augmentation de la synthèse d’oxyde nitrique cérébral participe à la pathogénèse des complications neurologiques de l’IHA (Chapitre 2.3, articles 3 et 4). 4. Des traitements anti-inflammatoires tels que l’hypothermie et la minocycline peuvent constituer de nouvelles approches thérapeutiques chez les patients atteints d’IHA (Chapitre 2.1, article 1; Chapitre 2.2, article 2). 5. Les effets bénéfiques de l’hypothermie et de la minocycline sur les complications neurologiques de l’IHA expérimentale s’expliquent, en partie, par une diminution du stress oxydatif/nitrosatif (Chapitre 2.3, article 3; Chapitre 2.4, article 4).

Mild hypothermia in the prevention of brain edema in acute liver failure: mechanisms and clinical prospects.

Mild hypothermia (32 degrees C-35 degrees C) reduces intracranial pressure in patients with acute liver failure and may offer an effective adjunct therapy in the management of these patients. Studies in experimental animals suggest that this beneficial effect of hypothermia is the result of a decrease in blood-brain ammonia transfer resulting in improvement in brain energy metabolism and normalization of glutamatergic synaptic regulation. Improvement in brain energy metabolism by hypothermia may result from a reduction in ammonia-induced decrease of brain glucose (pyruvate) oxidation. Restoration of normal glutamatergic synaptic regulation by hypothermia may be the consequence of the removal of ammonia-induced decreases in expression of astrocytic glutamate transporters resulting in normal glutamate neurotransmitter inactivation in brain. Randomized controlled clinical trials of hypothermia are required to further evaluate its clinical impact.

Mild hypothermia prevents cerebral edema and CSF lactate accumulation in acute liver failure.

Evidence from both clinical and experimental studies demonstrates that mild hypothermia prevents encephalopathy and brain edema in acute liver failure (ALF). As part of a series of studies to elucidate the mechanism(s) involved in this protective effect, groups of rats with ALF resulting from hepatic devascularization were maintained at either 37°C (normothermic) or 35°C (hypothermic), and neurological status was monitored in relation to cerebrospinal fluid (CSF) concentrations of ammonia and lactate. CSF was removed via implanted cisterna magna catheters. Mild hypothermia resulted in a delay in onset of encephalopathy and prevention of brain edema; CSF concentrations of ammonia and lactate were concomitantly decreased. Blood ammonia concentrations, on the other hand, were not affected by hypothermia in ALF rats. These findings suggest that brain edema and encephalopathy in ALF are the consequence of ammonia-induced impairment of brain energy metabolism and open the way for magnetic resonance spectroscopic monitoring of cerebral function in ALF. Mild hypothermia could be beneficial in the prevention of severe encephalopathy and brain edema in patients with ALF awaiting liver transplantation.

Mild hypothermia prevents brain edema and attenuates up-regulation of the astrocytic benzodiazepine receptor in experimental acute liver failure.

BACKGROUND/AIMS: Mild hypothermia has proven useful in the clinical management of patients with acute liver failure. Acute liver failure in experimental animals results in alterations in the expression of genes coding for astrocytic proteins including the "peripheral-type" (astrocytic) benzodiazepine receptor (PTBR), a mitochondrial complex associated with neurosteroid synthesis. To gain further insight into the mechanisms whereby hypothermia attenuates the neurological complications of acute liver failure, we investigated PTBR expression in the brains of hepatic devascularized rats under normothermic (37 degrees C) and hypothermic (35 degrees C) conditions. METHODS: PTBR mRNA was measured using semi-quantitative RT-PCR in cerebral cortical extracts and densities of PTBR sites were measured by quantitative receptor autoradiagraphy. Brain pregnenolone content was measured by radioimmunoassay. RESULTS: At coma stages of encephalopathy, animals with acute liver failure manifested a significant increase of PTBR mRNA levels. Brain pregnenolone content and [(3)H]PK 11195 binding site densities were concomitantly increased. Mild hypothermia prevented brain edema and significantly attenuated the increased receptor expression and pregnenolone content. CONCLUSIONS: These findings suggest that an attenuation of PTBR up-regulation resulting in the prevention of increased brain neurosteroid content represents one of the mechanisms by which mild hypothermia exerts its protective effects in ALF.

Systemic oxidative stress is implicated in the pathogenesis of brain edema in rats with chronic liver failure.

Chronic liver failure leads to hyperammonemia, a central component in the pathogenesis of hepatic encephalopathy (HE); however, a correlation between blood ammonia levels and HE severity remains controversial. It is believed oxidative stress plays a role in modulating the effects of hyperammonemia. This study aimed to determine the relationship between chronic hyperammonemia, oxidative stress, and brain edema (BE) in two rat models of HE: portacaval anastomosis (PCA) and bile-duct ligation (BDL). Ammonia and reactive oxygen species (ROS) levels, BE, oxidant and antioxidant enzyme activities, as well as lipid peroxidation were assessed both systemically and centrally in these two different animal models. Then, the effects of allopurinol (xanthine oxidase inhibitor, 100mg/kg for 10days) on ROS and BE and the temporal resolution of ammonia, ROS, and BE were evaluated only in BDL rats. Similar arterial and cerebrospinal fluid ammonia levels were found in PCA and BDL rats, both significantly higher compared to their respective sham-operated controls (p<0.05). BE was detected in BDL rats (p<0.05) but not in PCA rats. Evidence of oxidative stress was found systemically but not centrally in BDL rats: increased levels of ROS, increased activity of xanthine oxidase (oxidant enzyme), enhanced oxidative modifications on lipids, as well as decreased antioxidant defense. In PCA rats, a preserved oxidant/antioxidant balance was demonstrated. Treatment with allopurinol in BDL rats attenuated both ROS and BE, suggesting systemic oxidative stress is implicated in the pathogenesis of BE. Analysis of ROS and ammonia temporal resolution in the plasma of BDL rats suggests systemic oxidative stress might be an important "first hit", which, followed by increases in ammonia, leads to BE in chronic liver failure. In conclusion, chronic hyperammonemia and oxidative stress in combination lead to the onset of BE in rats with chronic liver failure.

Brain edema in acute liver failure and chronic liver disease: Similarities and differences.

Hepatic encephalopathy (HE) is a complex neuropsychiatric syndrome that typically develops as a result of acute liver failure or chronic liver disease. Brain edema is a common feature associated with HE. In acute liver failure, brain edema contributes to an increase in intracranial pressure, which can fatally lead to brain stem herniation. In chronic liver disease, intracranial hypertension is rarely observed, even though brain edema may be present. This discrepancy in the development of intracranial hypertension in acute liver failure versus chronic liver disease suggests that brain edema plays a different role in relation to the onset of HE. Furthermore, the pathophysiological mechanisms involved in the development of brain edema in acute liver failure and chronic liver disease are dissimilar. This review explores the types of brain edema, the cells, and pathogenic factors involved in its development, while emphasizing the differences in acute liver failure versus chronic liver disease. The implications of brain edema developing as a neuropathological consequence of HE, or as a cause of HE, are also discussed.

AST-120 (spherical carbon adsorbent) lowers ammonia levels and attenuates brain edema in bile duct-ligated rats

The pathogenesis of hepatic encephalopathy is multifactorial, involving gut-derived toxins such as ammonia, which has been demonstrated to induce oxidative stress. Therefore, a primary hepatic encephalopathy treatment target is reducing ammonia production in the gastrointestinal tract. AST-120, an oral adsorbent of engineered activated carbon microspheres with surface areas exceeding 1600 m(2) /g, acts as a sink for neurotoxins and hepatotoxins present in the gut. We evaluated the capacity of AST-120 to adsorb ammonia in vitro and to lower blood ammonia, oxidative stress and brain edema in cirrhotic rats. Cirrhosis was induced in rats by bile duct ligation for 6 weeks. AST-120 was administered by gavage preventively for 6 weeks (0.1, 1, and 4 g/kg/day). In addition, AST-120 was evaluated as a short-term treatment for 2 weeks and 3 days (1 g/kg/day) and as a sink to adsorb intravenously infused ammonium acetate. In vitro, AST-120 efficiently adsorbed ammonia. Ammonia levels significantly decreased in a dose-dependent manner for all AST-120-treated bile duct-ligated rats (nontreated: 177.3 ± 30.8 μM; AST-120, 0.1 g/kg/day: 121.9 ± 13.8 μM; AST-120, 1 g/kg/day: 80.9 ± 30.0 μM; AST-120, 4 g/kg/day: 48.8 ± 19.6 μM) and significantly correlated with doses of AST-120 (r = -0.6603). Brain water content and locomotor activity normalized after AST-120 treatments, whereas arterial reactive oxygen species levels remained unchanged. Furthermore, AST-120 significantly attenuated a rise in arterial ammonia after ammonium acetate administration (intravenously). Conclusion:AST-120 treatment decreased arterial ammonia levels, normalized brain water content and locomotor activity but did not demonstrate an effect on systemic oxidative stress. Also, AST-120 acts as an ammonia sink, efficiently removing blood-derived ammonia. Additional studies are warranted to evaluate the effects of AST-120 on hepatic encephalopathy in patients with advanced liver disease. (HEPATOLOGY 2011;).

Increased brain lactate is central to the development of brain edema in rats with chronic liver disease

The pathogenesis of brain edema in patients with chronic liver disease (CLD) and minimal hepatic encephalopathy (HE) remains undefined. This study evaluated the role of brain lactate, glutamine and organic osmolytes, including myo-inositol and taurine, in the development of brain edema in a rat model of cirrhosis.Six-week bile-duct ligated (BDL) rats were injected with (13)C-glucose and de novo synthesis of lactate, and glutamine in the brain was quantified using (13)C nuclear magnetic resonance spectroscopy (NMR). Total brain lactate, glutamine, and osmolytes were measured using (1)H NMR or high performance liquid chromatography. To further define the interplay between lactate, glutamine and brain edema, BDL rats were treated with AST-120 (engineered activated carbon microspheres) and dichloroacetate (DCA: lactate synthesis inhibitor).Significant increases in de novo synthesis of lactate (1.6-fold, p<0.001) and glutamine (2.2-fold, p<0.01) were demonstrated in the brains of BDL rats vs. SHAM-operated controls. Moreover, a decrease in cerebral myo-inositol (p<0.001), with no change in taurine, was found in the presence of brain edema in BDL rats vs. controls. BDL rats treated with either AST-120 or DCA showed attenuation in brain edema and brain lactate. These two treatments did not lead to similar reductions in brain glutamine.Increased brain lactate, and not glutamine, is a primary player in the pathogenesis of brain edema in CLD. In addition, alterations in the osmoregulatory response may also be contributing factors. Our results suggest that inhibiting lactate synthesis is a new potential target for the treatment of HE.

Prevalencia de edema pulmonar agudo en el embarazo y el puerperio

El edema pulmonar agudo durante el embarazo es una entidad que aunque no es muy común, produce una alta morbimortalidad tanto materna como fetal. Metodología Se realizó un estudio transversal para calcular la prevalencia del edema pulmonar agudo en el embarazo en la Clínica Orquídeas, tomando los datos en un periodo de tres años. Se analizaron las principales características y se calcularon las tasas de morbilidad. Resultados La prevalencia del edema pulmonar agudo es de 0.67/1000 pacientes que ingresan a UCI en la Clínica Orquídeas. La enfermedad asociada más común es la preeclampsia con el 81% de los casos, y el sobrepeso influye de forma notoria. El tipo de ventilación más usada fue ventilación mecánica invasiva con 71% Discusión La prevalencia de edema pulmonar durante el embarazo es mayor en el presente estudio, que en otras series, posiblemente debido a que los datos fueron calculados en una UCI obstétrica únicamente. Este estudio servirá como base para posteriores estudios analíticos, siendo el primero realizado en nuestro país.

Lesiones laríngeas post-intubación en adultos y su relación con el tiempo de intubación: Estudio de nasofibrolaringoscopia diagnóstica

Objetivo: Determinar las lesiones laríngeas post-intubación endotraqueal en la unidad de cuidado intensivo (UCI) y cirugía ambulatoria y evaluar su asociación con respecto al tiempo de intubación y otras variables clínico-demográficas en un hospital universitario. Materiales y métodos: Estudio de cohorte analítico incluyendo 60 pacientes (30 de UCI y 30 de cirugía ambulatoria) a quienes se les realizó nasofibrolaringoscopia a las 24 horas post-extubación y a las 3 semanas de control y se registran las lesiones laríngeas encontradas. Resultados: En la primera endoscopia el 70% de los pacientes de cirugía ambulatoria presentaban al menos una lesión laríngea con un promedio de duración de intubación de 0.12 días DS±0.05 desapareciendo todas las lesiones en la segunda endoscopia. En el análisis del grupo de UCI se encontraron lesiones en el 76.6% de los pacientes con un promedio de duración de intubación de 6.0 días DS±3.3. La presencia de edema en pacientes con intubación prolongada por más de 6 días mostró diferencias estadísticamente significativa con respecto al grupo con menos días de intubación (RR 3.048, 95% IC 0.9-9.3, P=0.03) al igual que con antecedente de EPOC (P=0.032) y APACHE II mayor de 17 (RR 1.8, 95% IC 1.114-3.0, P=0.013). EPOC tiene una diferencia estadísticamente significativa con hiperemia (P=0.02) y granuloma (P=0.019). En la segunda endoscopia se encontró mayor frecuencia de hiperemia en los pacientes con intubación prolongada (>6 días) con una diferencia estadísticamente significativa (P=0.01). Conclusión: La intubación prolongada se encuentra asociada a la aparición edema e hiperemia en la laringe. EPOC y puntaje superior de APACHE II se relacionan con hiperemia y granulomas glóticos.

Chlorpropamide treatment restores the reduced carrageenan-induced paw edema and pleural exudate volume in diabetic rats

Objective and design: Knowing that hyperglycemia is a hallmark of vascular dysfunction in diabetes and that neonatal streptozotocin-induced diabetic rats (n-STZ) present reduced inflammatory response, we decided to evaluate the effect of chlorpropamide-lowered blood glucose levels on carrageenan-induced rat paw edema and pleural exudate in n-STZ. Materials: Diabetes was induced by STZ injection (160 mg/kg, ip) in neonates (2-day-old) Wistar rats. Treatment: n-STZ diabetic rats were treated with chlorpropamide (200 mg/kg, 15 d, by gavage) 8 weeks after STZ injection. Methods: Carrageenan-induced paw edema and pleural exudate volumes were assessed concomitantly with peripheral and exudate leukocyte count. We also evaluated the expression of inducible nitric oxide synthase (iNOS) in lungs of all experimental groups. Results: Chlorpropamide treatment improved glucose tolerance, beta-cell function (assessed by HOMA-beta), corrected paw edema, and pleural exudate volume in n-STZ. Neither leukocyte count nor iNOS expression were affected by diabetes or by chlorpropamide treatment. Conclusion: Chlorpropamide treatment by restoring beta-cell function, reducing blood sugar levels, and improving glucose tolerance might be contributing to the correction of the reduced inflammatory response tested as paw edema and pleural exudate in n-STZ diabetic rats.

Gene expression profiling reveals molecular marker candidates of laryngeal squamous cell carcinoma

Laryngeal squamous cell carcinoma is very common in head and neck cancer, with high mortality rates and poor prognosis. In this study, we compared expression profiles of clinical samples from 13 larynx tumors and 10 non-neoplastic larynx tissues using a custom-built cDNA microarray containing 331 probes for 284 genes previously identified by informatics analysis of EST databases as markers of head and neck tumors. Thirty-five genes showed statistically significant differences (SNR >= 11.01, p <= 0.001) in the expression between tumor and non-tumor larynx tissue samples. Functional annotation indicated that these genes are involved in cellular processes relevant to the cancer phenotype, such as apoptosis, cell cycle, DNA repair, proteolysis, protease inhibition, signal transduction and transcriptional regulation. Six of the identified transcripts map to intronic regions of protein-coding genes and may comprise non-annotated exons or as yet uncharacterized long ncRNAs with a regulatory role in the gene expression program of larynx tissue. The differential expression of 10 of these genes (ADCY6, AES, AL2SCR3, CRR9, CSTB, DUSP1, MAP3K5, PLAT, UBL1 and ZNF706) was independently confirmed by quantitative real-time RT-PCR. Among these, the CSTB gene product has cysteine protease inhibitor activity that has been associated with an antimetastatic function. Interestingly, CSTB showed a low expression in the tumor samples analyzed (p<0.0001). The set of genes identified here contribute to a better understanding of the molecular basis of larynx cancer, and provide candidate markers for improving diagnosis, prognosis and treatment of this carcinoma.