Distribution of Transmissible Amyloid Proteins in the Liver with Apolipoprotein A-II Amyloidosis

Article信州医学雑誌 64(4): 183-194(2016)journal articl

Apolipoprotein A-II induces acute-phase response associated AA amyloidosis in mice through conformational changes of plasma lipoprotein structure

Abstract During acute-phase response (APR), there is a dramatic increase in serum amyloid A (SAA) in plasma high density lipoproteins (HDL). Elevated SAA leads to reactive AA amyloidosis in animals and humans. Herein, we employed apolipoprotein A-II (ApoA-II) deficient (Apoa2 −/− ) and transgenic (Apoa2Tg) mice to investigate the potential roles of ApoA-II in lipoprotein particle formation and progression of AA amyloidosis during APR. AA amyloid deposition was suppressed in Apoa2 −/− mice compared with wild type (WT) mice. During APR, Apoa2 −/− mice exhibited significant suppression of serum SAA levels and hepatic Saa1 and Saa2 mRNA levels. Pathological investigation showed Apoa2 −/− mice had less tissue damage and less inflammatory cell infiltration during APR. Total lipoproteins were markedly decreased in Apoa2 −/− mice, while the ratio of HDL to low density lipoprotein (LDL) was also decreased. Both WT and Apoa2 −/− mice showed increases in LDL and very large HDL during APR. SAA was distributed more widely in lipoprotein particles ranging from chylomicrons to very small HDL in Apoa2 −/− mice. Our observations uncovered the critical roles of ApoA-II in inflammation, serum lipoprotein stability and AA amyloidosis morbidity, and prompt consideration of therapies for AA and other amyloidoses, whose precursor proteins are associated with circulating HDL particles

Caloric restriction reduces the systemic progression of mouse AApoAII amyloidosis

<div><p>In mouse senile amyloidosis, apolipoprotein (Apo) A-II is deposited extracellularly in many organs in the form of amyloid fibrils (AApoAII). Reduction of caloric intake, known as caloric restriction (CR), slows the progress of senescence and age-related disorders in mice. In this study, we intravenously injected 1 μg of isolated AApoAII fibrils into R1.P1-<i>Apoa2c</i> mice to induce experimental amyloidosis and investigated the effects of CR for the next 16 weeks. In the CR group, AApoAII amyloid deposits in the liver, tongue, small intestine and skin were significantly reduced compared to those of the <i>ad libitum</i> feeding group. CR treatment led to obvious reduction in body weight, improvement in glucose metabolism and reduction in the plasma concentration of ApoA-II. Our molecular biological analyses of the liver suggested that CR treatment might improve the symptoms of inflammation, the unfolded protein response induced by amyloid deposits and oxidative stress. Furthermore, we suggest that CR treatment might improve mitochondrial functions via the sirtuin 1-peroxisome proliferator-activated receptor γ coactivator 1α (SIRT1-PGC-1α) pathway. We suggest that CR is a promising approach for treating the onset and/or progression of amyloidosis, especially for systemic amyloidosis such as senile AApoAII amyloidosis. Our analysis of CR treatment for amyloidosis should provide useful information for determining the cause of amyloidosis and developing effective preventive treatments.</p></div

CR treatment might reduce chronic inflammation, stress response, and unfolded protein response induced by amyloid deposits and upregulate mitochondrial function.

<p>Using quantitative real-time RT-PCR, we determined mRNA expression levels of the following genes in the liver after the intervention: inflammation-related genes (<i>Nfkb1</i>, <i>Tnfa</i>, <i>Il1b</i>, <i>Il6</i>, and <i>Tgfb1</i>), macrophage marker gene (<i>Adgre1</i>), stress response-related genes (<i>Ncf1</i> and <i>Ncf2</i>), autophagy-related gene (<i>Atg5</i>), unfolded protein response sensor gene (<i>Hspa5</i>) and mitochondrial function-related genes (<i>Ppargc1a</i>, <i>Sirt1</i>, and <i>Sirt3</i>). Each column and bar represents the mean ± S.D. (N = 6 (CR+F) and 5 (others)). *p<0.05, **p<0.01, ***p<0.001 (Tukey-Kramer method for multiple comparison).</p

CR treatment suppressed systemic progression of AApoAII deposits in mice.

<p>A single administration of 1 μg AApoAII fibrils was given to female mice. After 16 weeks, amyloid deposits were detected. (A) LM images of AApoAII deposits in several organs in mice. <i>Left-hand panels in each group</i>, Amyloid deposits were identified by green birefringence in Congo red-stained sections using polarized LM. <i>Right-hand panels in each group</i>, AApoAII deposits were confirmed immunohistochemically with anti-ApoA-II antiserum. Each scale bar indicates 100 μm. (B and C) The amyloid scores in several organs and the AI in whole bodies in mice. Each column represents the means (N = 5 (AL+F) and 6 (CR+F)). *p<0.05, **p<0.01 (non-parametric Mann-Whitney <i>U</i> test). (D) Comparison with positive areas of amyloid deposits in the liver and spleen using the immunohistochemical method with anti-ApoA-II anti-serum. Three areas in each liver and spleen section were randomly captured under x 200 magnification and the positive areas were calculated with the Image J system. Each column and bar represents the mean ± S.D. (N = 5 (AL+F) and 6 (CR+F)). *p<0.05, **p<0.001 (non-paired Student’s <i>t</i> test)<b>.</b></p

Experimental design and percent changes of BWs in mice from baseline during the CR intervention.

<p>CR treatment was performed by a step-down protocol to reach 60% of AL feeding levels, after which it was continued for 16 weeks. The induction of AApoAII amyloidosis in the AL+F and CR+F groups was performed when 60% CR was started. Each symbol and bar represents the mean ± S.D. (N = 6 (CR+F) or 5 (others)). P values were obtained by the Tukey-Kramer method for multiple comparison at corresponding time. *p<0.05, **p<0.01, ***p<0.001 vs. the AL+V group. #p<0.05, ##p<0.01, ###p<0.001 vs. the AL+F group.</p