Amiloidosis traqueobronquial: diagnóstico, tratamiento y evolución en 5 casos / Tracheobronchial amyloidosis: Diagnosis, treatment and evolution in 5 patients

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Modified immunotherapies against Alzheimer's disease: toward safer and effective amyloid clearance.

Alzheimer's disease (AD) is characterized by the deposition of amyloid plaques, loss of neurons, neuritic degeneration, accumulation of fibrillary tangles in neurons, and a progressive loss of cognitive function. Amyloid-ß peptide (Aß) appears to play a pivotal role in the development of AD. Clearance of Aß from the brain represents an important therapeutic strategy for prevention and treatment of AD. Immunotherapy targeting Aß is effective to remove the peptide from the brain. However, it is associated with detrimental adverse effects, such as autoimmune meningoencephalitis and microhemorrhage. These are presumably the results of brain infiltration of provoked autoimmune T lymphocytes in response to Aß vaccination and release of proinflammatory cytokines from microglia activated by the immune complex of Aß and antibodies. An improvement of the safety of the immunotherapy is a major goal of the immunotherapy study. Here, we review the mechanisms involved in modified immunological strategies, as well as their adverse effects. We discuss the following: the development of B epitope vaccines to avoid activation of autoimmune T lymphocytes; DNA vaccines containing appropriate immunostimulatory and immunomodulatory sequences to induce the desired humoral immune responses; antibody modifications to avoid activation of microglia and subsequent release of proinflammatory cytokines; single chain antibodybased gene therapy; immunotherapy targeting Aß oligomers; modulation of antibody delivery approach and dose; and application of autoantibodies against Aß. These ultimately represent future directions of therapeutic approaches toward safer and effective Aß clearance.

Gastric emptying and postprandial glucose excursions in adolescents with type 1 diabetes.

Because amylin is co-secreted with insulin from beta cells, patients with type 1 diabetes (T1DM) are deficient in both insulin and amylin. Amylin delays gastric emptying and suppresses glucagon in the postprandial period. Hence, we hypothesized that children with complication-naive T1DM have accelerated gastric emptying in response to a mixed meal because of amylin deficiency. Amylin, glucagon, insulin, glucose, and gastric emptying were measured in seven T1DM and in eight control subjects without diabetes. Subjects with T1DM had markedly elevated glucose concentrations when compared with controls (p < 0.0001). Amylin concentrations as predicted were lower in T1DM compared with those in controls (p < 0.0001). Insulin did not peak in the immediate postprandial period in T1DM when compared with controls (p < 0.0001). Glucagon concentrations did not significantly differ between groups. Interestingly, gastric velocity was delayed in patients with T1DM compared with controls (p < 0.01). In conclusion, subjects with T1DM do have amylin deficiency but this is not associated with accelerated gastric emptying as we had hypothesized but rather with delayed gastric emptying. Factors other than amylin play a role in control of gastric motility in T1DM. Subcutaneous insulin delivery fails to reach adequate concentrations in the postprandial period to curtail peak glucose concentration in T1DM.

Female-specific neuroprotection against transient brain ischemia observed in mice devoid of prion protein is abolished by ectopic expression of prion protein-like protein.

This study was designed to examine the function of cellular prion protein and prion protein-like protein/Doppel, in transient ischemia-related neuronal death in the hippocampus. Two different lines of mice devoid of cellular prion protein, Zrch I Prnp(0/0) and Ngsk Prnp(0/0), were used. The former lacks cellular prion protein whereas the latter ectopically expresses prion protein-like protein/Doppel in the brain in the absence of cellular prion protein. Mice were subjected to 10 min-occlusion of the bilateral common carotid arteries with recovery for 14 days. Less than 10% of the pyramidal neurons in the CA1 subfield were degenerated in male and female wild-type mice. In contrast, more than half of the neurons were lost in male Zrch I Prnp(0/0) and Ngsk Prnp(0/0) mice. Such severe neuronal loss was also observed in female Ngsk Prnp(0/0) mice. However, female Zrch I Prnp(0/0) mice showed mild neuronal loss similar to wild-type mice. Flunarizine, a T- and L-type Ca(2+)-channel antagonist, significantly reduced the neuronal loss in female but not in male Ngsk Prnp(0/0) mice. These results indicate that loss of cellular prion protein renders hippocampal neurons susceptible to ischemic insult specifically in male but not female mice and the ectopic expression of prion protein-like protein/Doppel aggravates the ischemic neuronal death in female prion protein-null mice probably via overloading of Ca(2+)-dependent signaling.

Cell-autonomous PrP-Doppel interaction regulates apoptosis in PrP gene-deficient neuronal cells.

The Prnd-encoded prion protein (PrP)-like protein, Doppel (Dpl), is a homologue of Prnp-encoded PrP, and is N-glycosylated protein with glycosylphosphatidylinositol anchor like PrP. Recently, ectopic expressions of Prnp/Prnd chimeric mRNAs have been identified as the cause of late-onset ataxia observed in several lines of Prnp-knockout mice such as ZrchII, Ngsk, Rcm0, and Rikn mice. However, it remains unclear whether the toxic effect of Dpl expression is a cell-autonomous mechanism but rather reflect a systemic process of heterogeneous cell population in the brain. In this study, the cell-autonomous role of Dpl was estimated by investigating PrP-deficient cells (HpL3-4)-the SV40 large T-antigen immortalized and Rikn Prnp(-/-) mice-derived neuronal cell line expressing Prnp/Prnd chimeric mRNAs. The reverse transcription polymerase chain reaction revealed that serum deprivation did not increase Prnp/Prnd chimeric mRNAs, which in fact was translated into a small amount of Dpl in HpL3-4 cells, whereas serum deprivation induced apoptotic cell death of HpL3-4 cells. Dpl overexpression enhanced apoptotic cell death, whereas the toxic effect of Dpl on apoptotic cell death was neutralized by PrP expression. These results indicate that Dpl elicited dose-dependently toxic effects on PrP-deficient cells without affecting on PrP-expressing cells, suggesting that the PrP-Dpl interaction can regulate cell death in a cell-autonomous manner.

Mice devoid of prion protein have cognitive deficits that are rescued by reconstitution of PrP in neurons.

Prion protein (PrP(C)) is a constituent of most normal mammalian cells and plays an essential role in the pathogenesis of transmissible spongiform encephalopathies (TSE). However, the normal cellular function of PrP(C) remains unclear. Here, we document that mice with a selective deletion of PrP(C) exhibited deficits in hippocampal-dependent spatial learning, but non-spatial learning remained intact. mPrP-/- mice also showed reduction in paired-pulse facilitation and long-term potentiation in the dentate gyrus in vivo. These deficits were rescued in transgenic mPrP-/- mice expressing PrP(C) in neurons under control of the neuron-specific enolase (NSE) promoter indicating that they were due to lack of PrP(C) function in neurons. The deficits were seen in mPrP-/- mice with a homogeneous 129/Ola background and in mPrP-/- mice in the mixed (129/Ola x C57BL/10) background indicating that these abnormalities were unlikely due to variability of background genes or alteration of the nearby Prnd (doppel) gene.

Cells release prions in association with exosomes.

Prion diseases are infectious neurodegenerative disorders linked to the accumulation in the central nervous system of the abnormally folded prion protein (PrP) scrapie (PrPsc), which is thought to be the infectious agent. Once present, PrPsc catalyzes the conversion of naturally occurring cellular PrP (PrPc) to PrPsc. Prion infection is usually initiated in peripheral organs, but the mechanisms involved in infectious spread to the brain are unclear. We found that both PrPc and PrPsc were actively released into the extracellular environment by PrP-expressing cells before and after infection with sheep prions, respectively. Based on Western blot with specific markers, MS, and morphological analysis, our data revealed that PrPc and PrPsc in the medium are associated with exosomes, membranous vesicles that are secreted upon fusion of multivesicular endosomes with the plasma membrane. Furthermore, we found that exosomes bearing PrPsc are infectious. Our data suggest that exosomes may contribute to intercellular membrane exchange and the spread of prions throughout the organism.

Unaltered pancreatic islet blood perfusion in islet amyloid polypeptide-deficient mice.

OBJECTIVE: Several biological activities have been ascribed to islet amyloid polypeptide (IAPP). However, their physiological relevance remains unclear. Previous studies in rats with exogenous administration of IAPP suggest that the peptide may increase splanchnic vascular resistance and redistribute the blood flow within the pancreas to the islets. In this study, the use of IAPP-deficient mice allowed us to evaluate possible effects of the lack of IAPP on splanchnic blood perfusion and we could thereby circumvent the potentially pharmacological actions of exogenously administered IAPP. DESIGN: Regional splanchnic blood flow was measured after exogenous administration of IAPP and in IAPP-deficient mice. METHODS: Blood flow values were determined using a non-radioactive microsphere technique in anesthetized animals. RESULTS: No differences in whole pancreatic blood flow or islet blood flow could be detected in IAPP-deficient mice when compared with control mice; neither did IAPP deficiency affect the glucose-induced increase in islet blood flow. Duodenal, ileal and colonic blood flows were similar in IAPP-deficient and control mice. Exogenous administration of IAPP selectively increased islet blood flow in wild-type control mice. CONCLUSIONS: The present findings in the IAPP-deficient mice suggest that the vascular effects seen in the islets after exogenous administration of IAPP to normal mice reflect pharmacological, rather than physiological effects of the peptide. We conclude that the lack of endogenous IAPP within the splanchnic vascular system does not alter the blood perfusion of pancreatic islets or other splanchnic organs.

Islet amyloid polypeptide (amylin)-deficient mice develop a more severe form of alloxan-induced diabetes.

To examine whether islet amyloid polypeptide (IAPP), other than through amyloid formation, may be of importance in diabetes pathogenesis, IAPP-deficient mice (IAPP(-/-)) were challenged with alloxan (day 0). Diabetes in IAPP(-/-) mice was more severe at day 35, indicated by greater weight loss; glucose levels were higher in alloxan-treated IAPP(-/-) mice, whereas insulin levels were lower, indicating a greater impairment of islet function. Accordingly, glucose levels upon intravenous glucose challenges at days 7 and 35 were consistently higher in alloxan-treated IAPP(-/-) mice. At day 35, insulin mRNA expression, but not beta-cell mass, was lower in untreated IAPP(-/-) mice. Yet, upon alloxan administration, beta-cell mass and numbers of beta-cell-containing islets were significantly more reduced in IAPP(-/-) mice. Furthermore, they displayed exaggerated beta-cell dysfunction, because in their remaining beta-cells, insulin mRNA expression was significantly more impaired and the localization of glucose transporter-2 was perturbed. Thus the lack of IAPP has allowed exaggerated beta-cell cytotoxic actions of alloxan, suggesting that there may be beneficial features of IAPP actions in situations of beta-cell damage.

Clinical implications of amylin and amylin deficiency.

PURPOSE: This paper presents an overview of the physiology of glycemic control and the mechanisms of amylin deficiency in people with diabetes. Benefits of replacement therapy with both pramlintide and insulin are discussed. METHODS: The discovery of the pancreatic beta-cell hormone amylin, which is cosecreted with insulin in response to hyperglycemia, has prompted a reanalysis of the mechanisms underlying the control of glucose homeostasis. A review of the current literature on amylin and amylin deficiency provides the basis of this reanalysis, with a discussion of the clinical implications for people with diabetes. RESULTS: Amylin appears to work with insulin to regulate plasma glucose concentrations in the bloodstream, suppressing the postprandial secretion of glucagon and restraining the rate of gastric emptying. People with diabetes have a deficiency in the secretion of amylin that parallels the deficiency in insulin secretion, resulting in an excessive inflow of glucose into the bloodstream during the postprandial period. CONCLUSIONS: While insulin replacement therapy is a cornerstone of diabetes treatment, replacement of the function of both amylin and insulin may allow a more complete restoration of the normal physiology of glucose control.

Increased insulin secretion and glucose tolerance in mice lacking islet amyloid polypeptide (amylin).

Islet amyloid polypeptide (IAPP or amylin) is costored and cosecreted with insulin and may regulate insulin secretion and blood glucose handling. However, the role and importance of endogenous IAPP in the regulation of insulin release and glucose homeostasis have been controversial. Here we report on the generation and phenotypic analysis of IAPP-deficient mice. These mice have normal, or near to normal, basal levels of circulating insulin and glucose. However, following glucose administration, IAPP-deficient males presented increased insulin responses paralleled with a more rapid blood glucose elimination compared to wild-type controls. Blood glucose elimination was also found to be enhanced in IAPP-deficient females, but the insulin response in this gender did not differ from controls. In a transgenic rescue experiment, using an insulin-promoter human-IAPP fusion gene, insulin responses and blood glucose elimination were reversed in IAPP-deficient males, whereas the female phenotype appeared unaffected. Our results provide the first firm evidence of a physiological role for endogenous IAPP and indicate that IAPP, apparently in a gender-dependent manner, limits the degree of glucose-induced insulin secretion and the rate of blood glucose elimination.

Microheterogeneity of serum glycoproteins and their liver precursors in patients with carbohydrate-deficient glycoprotein syndrome type I: apparent deficiencies in clusterin and serum amyloid P.

Serum and liver protein patterns were studied, respectively, in 5 patients (serum) and 1 patient (liver) with carbohydrate-deficient glycoprotein syndrome (CDGS) type I by high-resolution two-dimensional electrophoresis (2-DE) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The pattern of serum glycoproteins in all 5 patients presented abnormal trains of isoforms with decreased mass (delta molecular weight 3000) and all showed a cathodal shift. Two-dimensional electrophoresis and SDS-PAGE mass analysis of transferrin, alpha1 -antitrypsin, haptoglobin beta-chain, and alpha1-acid glycoprotein after neuraminidase and N-glycosidase F treatments demonstrated that the additional trains of the isoforms found in CDGS type I contain homologous species of isoforms. Some of them still showed charge differences, and all still contained glycans except for transferrin, with some unusual nonglycosylated isoforms. In addition, deficiencies in clusterin and serum amyloid P, not described so far, have been found in all 5 patients. The two-dimensional pattern of immunodetected precursors of serum proteins in liver cells from 1 patient with CDGS showed abnormal low-mass precursors and the absence of the precursors normally found in controls. These results suggest that these abnormal precursors accumulate during the early oligosaccharide processing of the nascent protein-bound oligosaccharides and that glycoprotein precursors undergo an altered intracellular transport while the post-translational processing along the normal pathway is still apparently functioning in patients with CDGS.

Sleep and sleep regulation in normal and prion protein-deficient mice.

Mice are the preferred mammalian species for genetic investigations of the role of proteins. The normal function of the prion protein (PrP) is unknown, although it plays a major role in the prion diseases, including fatal familial insomnia. We investigated its role in sleep and sleep regulation by comparing baseline recordings and the effects of sleep deprivation in PrP knockout mice (129/SV) and wild-type controls (129/SV x C57BL/6), which are the mice used for most gene targeting experiments and whose behavior is not well characterized. Although no difference was evident in the amount of vigilance states, the null mice exhibited a larger degree of sleep fragmentation than the wild-type with almost double the amount of short waking episodes. As in other rodents, cortical temperature closely reflected the time course of waking. The increase of slow-wave activity (SWA; mean EEG power density in the 0.25-4.0 Hz range) at waking to nonrapid eye movement (NREM) sleep transitions was faster and reached a lower level in the null mice than in the wild-type. The contribution of the lower frequencies (0.25-5.0 Hz) to the spectrum was smaller than in other rodents in all three vigilance states, and the distinction between NREM sleep and REM sleep was most marked in the theta band. After the sleep deprivation, SWA was increased, but the changes in EEG power density and SWA were more prominent and lasted longer in the PrP-null mice. Our results suggest that PrP plays a role in promoting sleep continuity.

Prion protein (PrP) with amino-proximal deletions restoring susceptibility of PrP knockout mice to scrapie.

The 'protein only' hypothesis postulates that the prion, the agent causing transmissible spongiform encephalopathies, is PrP(Sc), an isoform of the host protein PrP(C). Protease treatment of prion preparations cleaves off approximately 60 N-terminal residues of PrP(Sc) but does not abrogate infectivity. Disruption of the PrP gene in the mouse abolishes susceptibility to scrapie and prion replication. We have introduced into PrP knockout mice transgenes encoding wild-type PrP or PrP lacking 26 or 49 amino-proximal amino acids which are protease susceptible in PrP(Sc). Inoculation with prions led to fatal disease, prion propagation and accumulation of PrP(Sc) in mice expressing both wild-type and truncated PrPs. Within the framework of the 'protein only' hypothesis, this means that the amino-proximal segment of PrP(C) is not required either for its susceptibility to conversion into the pathogenic, infectious form of PrP or for the generation of PrP(Sc).

Amylin/islet amyloid polypeptide: biochemistry, physiology, patho-physiology.

Amylin is a 37 amino-acid peptide mainly produced by the islet beta-cell. Aggregation of amylin is partly responsible for amyloid formation. Amyloid deposits occur both extracellularly and intracellularly and may contribute to beta-cell degeneration. Amylin is packed in beta-cell granules and cosecreted with insulin in response to the same stimuli but, unlike other beta-cell products, it is produced from specific a gene on chromosome 12. Basal, plasma amylin concentrations are around 5 pM, and increase fourfold after meals or glucose. Higher levels are found in cases of insulin resistance, obesity, gestational diabetes and in some patients with NIDDM. Low or absent levels are found in insulin-dependent diabetic patients. There are similarities between amylin and non beta-cell peptides such as calcitonin gene related peptides (CGRP). They may bind to the same receptor, determine similar post-receptor phenomena and qualitatively similar actions but with different degree of potency. The actions of amylin are multiple and mostly exerted in the regulation of fuel metabolism. In muscle, amylin opposes glycogen synthesis, activates glycogenolysis and glycolysis (increasing lactate production). Consequently, amylin increases lactate output by muscle and increases the plasma lactate concentration. In fasting conditions, this lactate may serve as a gluconeogenic substrate for the liver, contributing to replenish depleted glycogen stores and to increase glucose production. In non-fasting conditions, lactate can be transformed by liver in triglycerides. It is not clear at present whether amylin actions on the liver are direct or mediated by changes in circulating metabolites. A probably indirect effect of amylin in muscle is to decrease insulin- (or glucose)-induced glucose uptake, which may contribute to insulin resistance. Other actions include inhibition of glucose-stimulated insulin secretion and, in general, actions mimicking CGRP effects. Some of these actions are seen at supraphysiological concentrations. The physiopathological consequences of amylin deficiency, or excess are under active by investigated.

Structure and biology of amylin.

Amylin is a recently discovered 37 amino acid peptide secreted into the bloodstream, along with insulin, from pancreatic beta-cells. It is about 50% identical to calcitonin gene-related peptides (CGRP alpha and CGRP beta) and structurally related to the calcitonins. Amylin can elicit the vasodilator effects of CGRP and the hypocalcaemic actions of calcitonin, while these peptides can mimic newly discovered actions of amylin on carbohydrate metabolism. The different relative potencies of these peptides suggest that they act with different selectivities at a family of receptors. Amylin is deficient in insulin-dependent diabetes mellitus, while plasma levels are elevated in insulin-resistant conditions such as obesity and impaired glucose tolerance. In this Viewpoint article, Tim Rink and colleagues propose that amylin is an endocrine partner to insulin and glucagon; deficiency or excess of amylin may therefore contribute to important metabolic diseases.

Amylin and insulin co-replacement therapy for insulin-dependent (type I) diabetes mellitus.

Amylin is a proteinaceous hormone secreted form insulin-producing pancreatic beta-cells following stimulation by food molecules such as glucose and arginine. Amylin decreases insulin-stimulated glucose uptake in skeletal muscle and counteracts the ability of insulin to suppress output of glucose from the liver. Substantial evidence supports the view that maylin is a second glucoregulatory hormone produced from islet beta-cells, which can modulate a number of metabolic processes also regulated by insulin. The islet beta-cell may therefore transmit a dual message to peripheral tissues through the two hormones, insulin and amylin. Like insulin, amylin is deficient in individuals with autoimmune diabetes mellitus. Since amylin can modulate processes of fuel metabolism in key tissues, amylin deficiency could contribute to the clinical course in patients with autoimmune diabetes. Here, I propose that amylin lack plays a significant role to promote the tendency to hypoglycemia and defective glycemic control characteristic of insulin-treated patients with autoimmune diabetes. Treatment of such diabetics with injections of amylin as well as insulin is being evaluated with the aim of lessening the incidence and severity of hypoglycemia and improving glycemic control.