Vascular dysfunction induced by AGE is mediated by VEGF via mechanisms involving reactive oxygen species, guanylate cyclase, and protein kinase C

OBJECTIVE: These experiments were designed to elucidate mechanisms mediating vascular dysfunction induced by advanced glycation end products (AGEs). METHODS: Skin chambers were mounted on the backs of Sprague-Dawley rats and 1 week later, granulation tissue that formed in the bottom of the chamber was exposed twice daily for 7 days to glycated rat serum albumin in the presence and absence of inhibitors of reactive oxygen intermediates, nitric oxide synthase and guanylate cyclase, protein kinase C (PKC), and a neutralizing vascular endothelial growth factor (VEGF) antibody. Vascular (125)I-albumin clearance and blood flow were quantified by use of a double isotope-dilution technique and radiolabeled microspheres, respectively. RESULTS: Albumin permeation and blood flow were increased dose-dependently to a maximum of 2 to 3 times controls by increasing the extent of glucose modification, the concentration, or the duration of exposure to glycated albumin. These increases were significantly attenuated by probucol and superoxide dismutase; N(G)-nitro-L-arginine-methyl ester (L-NAME), a nitric oxide synthase inhibitor; LY83583, a guanylate cyclase inhibitor; and LY333531, a beta-isoform-selective protein kinase C inhibitor. A neutralizing VEGF monoclonal antibody also markedly attenuated the permeability and blood flow increases induced by glycated albumin. CONCLUSIONS: These observations indicate potentially important roles for oxygen free-radicals and nitric oxide in mediating permeability and blood flow changes induced by glycated proteins via mechanisms involving increased protein kinase C activity and VEGF production. Striking similarities in the mechanism by which hyperglycemia and glycated proteins induce vascular dysfunction suggest that a common pathway mediates effects of these different metabolic imbalances on vascular dysfunction.     

Stability of cerebral blood flow and oxygen metabolism during normal aging

Cerebral blood flow and oxygen metabolism in aged normal subjects were measured with positron emission tomography and their relationship with brain atrophy was evaluated. Brain atrophy progressed in a linear fashion during aging while cerebral blood flow and oxygen metabolism were well preserved. The finding suggests that brain atrophy is an aging process less dependent on cerebral blood flow and metabolism over the course of normal aging.     

Biochemical markers in the follow-up of medullary thyroid cancer.

Medullary thyroid cancer (MTC) shares biochemical features with other neuroendocrine tumors but the particular characteristics are largely unexplored. We investigated the biochemical neuroendocrine profile of MTC and whether specific markers could be useful in follow-up. In addition to the standard tumor marker calcitonin, plasma carcino-embryonic antigen (CEA), plasma catecholamines, (platelet) serotonin, chromogranin A, tryptase, and urinary markers of catecholamine, histamine, and serotonin metabolism were prospectively determined in 46 patients with histologically proven MTC. Patients were divided according to the stage of disease: group 1, no evidence; group 2, stable disease (SD); and group 3, progressive disease (PD). Plasma dopamine was increased in the majority of the patients with SD and PD; however it did not correlate with extent of disease. Elevated plasma platelet levels of serotonin were only present in patients with multiple endocrine neoplasia 2 with SD or PD but did not differ between those groups. Histamine metabolites were elevated in 20% of patients with SD and PD. In addition to plasma calcitonin, only CEA and chromogranin A could differentiate between stable and progressive MTC. MTCs are capable of synthesizing catecholamines, serotonin, and histamine metabolites underscoring that MTCs have metabolic characteristics in common with other neuroendocrine tumors. Thus far, clinical usefulness and relevance seems limited. The most useful markers in the follow-up of MTC are plasma calcitonin and CEA.     

Identification and management of invasive mycoses in internal medicine: a road-map for physicians

Invasive mycoses are a rising problem, not only in traditional categories of patients like hematologic or neutropenic ones, but also in elderly non-neutropenic patients admitted to internal medicine wards. Patients being admitted to medical wards are usually older, have multiple comorbidities, e.g., liver cirrhosis or chronic obstructive respiratory disease, may be malnourished or receive peripheral or total parenteral nutrition, and frequently are undergoing chronic corticosteroid therapy, chemotherapy for cancer or monoclonal antibodies for autoimmune diseases. Such risk factors may be contemporarily present in a single patient increasing the risk for the development of invasive mycoses. Diagnosis of candidemia and invasive aspergillosis is particularly difficult in patients hospitalized on medical wards, since symptoms and signs have low specificity, and most diagnostic tests have been only validated in neutropenic hematologic patients, but not in those without neutropenia. Both candidemia and invasive aspergillosis carry significant morbidity and mortality. The aim of this paper is to provide a simple guide to physicians for a prompt identification and treatment of patients with possible or suspected invasive mycoses.     

Endoscopic ultrasonography-guided transmural drainage of an infected hepatic cyst due to Edwardsiella tarda: a case report

Infected hepatic cysts are very rare compared to simple liver cysts and abscesses. We treated a 77-year-old man with an infected hepatic cyst in the lateral segment caused by Edwardsiella tarda, which has not been previously reported as a pathogenic organism associated with infected hepatic cysts. Percutaneous drainage was temporarily effective, but infection recurred after the drainage tube was removed. We then inserted two drainage tubes into the cyst using an endoscopic ultrasonography (EUS)-guided technique, which was developed from EUS-guided fine needle aspiration (EUS-FNA). The internal drainage tube was a 7 Fr double pigtail stent, and the external tube was a 6 Fr nasobiliary drainage tube. Lavage through the external drainage tube was carried out for one week. The external drainage tube was discontinued when the patient’s condition improved significantly. Sixteen days after tube insertion, he was discharged with the internal tube draining the hepatic cyst into the stomach. Fifteen months after EUS-guided drainage, CT examination showed no recurrence of the hepatic cyst. EUS-guided drainage is an effective treatment for infected hepatic cysts.     

Delaying aging and the aging-associated decline in protein homeostasis by inhibition of tryptophan degradation

Toxicity of aggregation-prone proteins is thought to play an important role in aging and age-related neurological diseases like Parkinson and Alzheimer's diseases. Here, we identify tryptophan 2,3-dioxygenase (tdo-2), the first enzyme in the kynurenine pathway of tryptophan degradation, as a metabolic regulator of age-related α-synuclein toxicity in a Caenorhabditis elegans model. Depletion of tdo-2 also suppresses toxicity of other heterologous aggregation-prone proteins, including amyloid-β and polyglutamine proteins, and endogenous metastable proteins that are sensors of normal protein homeostasis. This finding suggests that tdo-2 functions as a general regulator of protein homeostasis. Analysis of metabolite levels in C. elegans strains with mutations in enzymes that act downstream of tdo-2 indicates that this suppression of toxicity is independent of downstream metabolites in the kynurenine pathway. Depletion of tdo-2 increases tryptophan levels, and feeding worms with extra l-tryptophan also suppresses toxicity, suggesting that tdo-2 regulates proteotoxicity through tryptophan. Depletion of tdo-2 extends lifespan in these worms. Together, these results implicate tdo-2 as a metabolic switch of age-related protein homeostasis and lifespan. With TDO and Indoleamine 2,3-dioxygenase as evolutionarily conserved human orthologs of TDO-2, intervening with tryptophan metabolism may offer avenues to reducing proteotoxicity in aging and age-related diseases.