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Why are some amyloidoses systemic? Does hepatic "chaperoning at a distance" prevent cardiac deposition in a transgenic model of human senile systemic (transthyretin) amyloidosis?

ABSTRACT: In the human systemic amyloidoses caused by mutant or wild-type transthyretin (TTR), deposition occurs at a distance from the site of synthesis. The TTR synthesized and secreted by the hepatocyte circulates in plasma, then deposits in target tissues far from the producing cell, a pattern reproduced in mice transgenic for multiple copies of the human wild-type TTR gene. By 2 yr of age, half of the transgenic males show cardiac deposition resembling human senile systemic amyloidosis. However, as early as 3 mo of age, when there are no deposits, cardiac gene transcription differs from that of nontransgenic littermates, primarily in the expression of a large number of genes associated with inflammation and the immune response. At 24 mo, the hearts with histologically proven TTR deposits show expression of stress response genes, exuberant mitochondrial gene transcription, and increased expression of genes associated with apoptosis, relative to the hearts without TTR deposition. These 24-mo-old hearts with TTR deposits also show a decrease in transcription of inflammatory genes relative to that in the younger transgenic mice. After 2 yr of expressing large amounts of human TTR, the livers of the transgenic mice without cardiac deposition display chaperone gene expression and evidence of an activated unfolded protein response, while the livers of animals with cardiac TTR deposition display neither, showing increased transcription of interferon-responsive inflammatory genes and those encoding an antioxidant response. With time, in animals with cardiac deposition, it appears that hepatic proteostatic capacity is diminished, exposing the heart to a greater load of misfolded TTR with subsequent extracellular deposition. Hence systemic (cardiac) TTR deposition may be the direct result of the diminution in the distant chaperoning capacity of the liver related to age or long-standing exposure to misfolded TTR, or both.

SUBMITTER: Buxbaum JN

PROVIDER: S-EPMC3360152 | biostudies-other | 2012 Jun

REPOSITORIES: biostudies-other

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Why are some amyloidoses systemic? Does hepatic "chaperoning at a distance" prevent cardiac deposition in a transgenic model of human senile systemic (transthyretin) amyloidosis?

Buxbaum Joel N JN Tagoe Clement C Gallo Gloria G Walker John R JR Kurian Sunil S Salomon Daniel R DR

FASEB journal : official publication of the Federation of American Societies for Experimental Biology 20120223 6

In the human systemic amyloidoses caused by mutant or wild-type transthyretin (TTR), deposition occurs at a distance from the site of synthesis. The TTR synthesized and secreted by the hepatocyte circulates in plasma, then deposits in target tissues far from the producing cell, a pattern reproduced in mice transgenic for multiple copies of the human wild-type TTR gene. By 2 yr of age, half of the transgenic males show cardiac deposition resembling human senile systemic amyloidosis. However, as e ...[more]

PMID: 22362898

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Project description:AimsCardiac transthyretin amyloidosis (ATTR-CM) is a progressive and fatal condition. Prognosis can be determined at diagnosis according to the National Amyloidosis Centre (NAC) transthyretin amyloidosis (ATTR) stage. We sought to examine how NAC ATTR stage changes during follow-up and whether it maintains its prognostic value throughout the disease course.Methods and resultsWe performed a retrospective study of 945 patients with wild-type ATTR-CM (wtATTR-CM) or hereditary ATTR-CM associated with the V122I variant (V122I-hATTR-CM) who were diagnosed and serially evaluated at the UK NAC. Patients who commenced any disease-modifying therapy for amyloidosis were censored at the time of doing so. Landmark Kaplan-Meier survival analyses were performed at diagnosis (n = 945) and at 6 ± 1 (n = 432), 12 ± 3 (n = 562), and 24 ± 3 (n = 316) months and stratified by recalculated NAC ATTR stage at the relevant time point. Cox regression analyses were performed to assess the prognostic significance during follow-up of an increase in NAC ATTR stage from Stage I at diagnosis. Mortality in ATTR-CM was predicted by NAC ATTR stage at each time point [Stage II vs. I, hazard ratios (HRs) 1.95-2.67; P < 0.001; Stage III vs. II, HRs 1.64-2.25; P < 0.001-0.013]. An increase from NAC ATTR Stage I, which occurred in 21%, 32%, and 44% of evaluable patients at 6, 12, and 24 months of follow-up respectively, was highly predictive of ongoing mortality at each time point (HRs 2.58-3.22; P < 0.001) and in each genotypic subgroup (HRs 1.86-4.38; P < 0.05). Increase in NAC ATTR stage occurred earlier in V122I-hATTR-CM than in wtATTR-CM (43% vs. 27% at 12 months of follow-up; P = 0.003).ConclusionsNational Amyloidosis Centre ATTR stage predicts ongoing survival throughout the disease natural history in ATTR-CM, and an increase from NAC ATTR Stage I at diagnosis to a higher NAC ATTR stage predicts mortality throughout follow-up. Serial calculation of NAC ATTR stage suggests a more aggressive phenotype in V122I-hATTR-CM than in wtATTR-CM.

Project description:Dysregulation of neuropeptides may play an important role in aging-induced impairments. Among them, pituitary adenylate cyclase-activating polypeptide (PACAP) is a potent cytoprotective peptide that provides an endogenous control against a variety of tissue-damaging stimuli. We hypothesized that the progressive decline of PACAP throughout life and the well-known general cytoprotective effects of PACAP lead to age-related pathophysiological changes in PACAP deficiency, supported by the increased vulnerability to various stressors of animals partially or totally lacking PACAP. Using young and aging CD1 PACAP knockout (KO) and wild type (WT) mice, we demonstrated pre-senile amyloidosis in young PACAP KO animals and showed that senile amyloidosis appeared accelerated, more generalized, more severe, and affected more individuals. Histopathology showed age-related systemic amyloidosis with mainly kidney, spleen, liver, skin, thyroid, intestinal, tracheal, and esophageal involvement. Mass spectrometry-based proteomic analysis, reconfirmed with immunohistochemistry, revealed that apolipoprotein-AIV was the main amyloid protein in the deposits together with several accompanying proteins. Although the local amyloidogenic protein expression was disturbed in KO animals, no difference was found in laboratory lipid parameters, suggesting a complex pathway leading to increased age-related degeneration with amyloid deposits in the absence of PACAP. In spite of no marked inflammatory histological changes or blood test parameters, we detected a disturbed cytokine profile that possibly creates a pro-inflammatory milieu favoring amyloid deposition. In summary, here we describe accelerated systemic senile amyloidosis in PACAP gene-deficient mice, which might indicate an early aging phenomenon in this mouse strain. Thus, PACAP KO mice could serve as a model of accelerated aging with human relevance. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Dataset Information

Why are some amyloidoses systemic? Does hepatic "chaperoning at a distance" prevent cardiac deposition in a transgenic model of human senile systemic (transthyretin) amyloidosis?

Publications

Why are some amyloidoses systemic? Does hepatic "chaperoning at a distance" prevent cardiac deposition in a transgenic model of human senile systemic (transthyretin) amyloidosis?

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