Glycosylated apolipoprotein J in cardiac ischaemia: molecular processing and circulating levels in patients with acute ischaemic events

Aim Using proteomics, we previously found that serum levels of glycosylated (Glyc) forms of apolipoprotein J (ApoJ), a cytoprotective and anti-oxidant protein, decrease in the early phase of acute myocardial infarction (AMI). We aimed to investigate: (i) ApoJ-Glyc intracellular distribution and secretion during ischaemia; (ii) the early changes in circulating ApoJ-Glyc during AMI; and (iii) associations between ApoJ-Glyc and residual ischaemic risk post-AMI. Methods and results Glycosylated apolipoprotein J was investigated in: (i) cells from different organ/tissue origin; (ii) a pig model of AMI; (iii) de novo AMI patients (n = 38) at admission within the first 6 h of chest pain onset and without troponin T elevation at presentation (early AMI); (iv) ST-elevation myocardial infarction patients (n = 212) who were followed up for 6 months; and (v) a control group without any overt cardiovascular disease (n = 144). Inducing simulated ischaemia in isolated cardiac cells resulted in an increased intracellular accumulation of non-glycosylated ApoJ forms. A significant decrease in ApoJ-Glyc circulating levels was seen 15 min after ischaemia onset in pigs. Glycosylated apolipoprotein J levels showed a 45% decrease in early AMI patients compared with non-ischaemic patients (P < 0.0001), discriminating the presence of the ischaemic event (area under the curve: 0.934; P < 0.0001). ST-elevation myocardial infarction patients with lower ApoJ-Glyc levels at admission showed a higher rate of recurrent ischaemic events and mortality after 6-month follow-up (P = 0.008). Conclusions These results indicate that ischaemia induces an intracellular accumulation of non-glycosylated ApoJ and a reduction in ApoJ-Glyc secretion. Glycosylated apolipoprotein J circulating levels are reduced very early after ischaemia onset. Its continuous decrease indicates a worsening in the evolution of the cardiac event, likely identifying patients with sustained ischaemia after AMI.

Sterol O-acyltransferase 2 chaperoned by apolipoprotein J facilitates hepatic lipid accumulation following viral and nutrient stresses

The risks of non-alcoholic fatty liver disease (NAFLD) include obese and non-obese stresses such as chronic hepatitis C virus (HCV) infection, but the regulatory determinants remain obscure. Apolipoprotein J (ApoJ) served as an ER-Golgi contact-site chaperone near lipid droplet (LD), facilitating HCV virion production. We hypothesized an interplay between hepatic ApoJ, cholesterol esterification and lipid deposit in response to NAFLD inducers. Exposures of HCV or free-fatty acids exhibited excess LDs along with increased ApoJ expression, whereas ApoJ silencing alleviated hepatic lipid accumulation. Both stresses could concomitantly disperse Golgi, induce closer ApoJ and sterol O-acyltransferase 2 (SOAT2) contacts via the N-terminal intrinsically disordered regions, and increase cholesteryl-ester. Furthermore, serum ApoJ correlated positively with cholesterol and low-density lipoprotein levels in normal glycaemic HCV patients, NAFLD patients and in mice with steatosis. Taken together, hepatic ApoJ might activate SOAT2 to supply cholesteryl-ester for lipid loads, thus providing a therapeutic target of stress-induced steatosis.

Both Amyloid-β Peptide and Tau Protein Are Affected by an Anti-Amyloid-β Antibody Fragment in Elderly 3xTg-AD Mice

Alzheimer’s disease (AD) is the most common dementia worldwide. According to the amyloid hypothesis, the early accumulation of the Aβ-peptide triggers tau phosphorylation, synaptic dysfunction, and eventually neuronal death leading to cognitive impairment, as well as behavioral and psychological symptoms of dementia. ScFv-h3D6 is a single-chain variable fragment that has already shown its ability to diminish the amyloid burden in 5-month-old 3xTg-AD mice. However, tau pathology is not evident at this early stage of the disease in this mouse model. In this study, the effects of scFv-h3D6 on Aβ and tau pathologies have been assessed in 22-month-old 3xTg-AD mice. Briefly, 3xTg-AD female mice were treated for 2 weeks with scFv-h3D6 and compared with 3xTg-AD and non-transgenic (NTg) mice treated with PBS. The treatment with scFv-h3D6 was unequivocally effective in reducing the area of Aβ staining. Furthermore, a tendency for a reduction in tau levels was also observed after treatment that points to the interplay between Aβ and tau pathologies. The pro-inflammatory state observed in the 3xTg-AD mice did not progress after scFv-h3D6 treatment. In addition, the treatment did not alter the levels of apolipoprotein E or apolipoprotein J. Thus, a 2-week treatment with scFv-h3D6 was able to reduce AD-like pathology in elderly 3xTg-AD female mice.

Subcutaneous Administration of Apolipoprotein J-Derived Mimetic Peptide d-[113–122]apoJ Improves LDL and HDL Function and Prevents Atherosclerosis in LDLR-KO Mice

Mimetic peptides are potential therapeutic agents for atherosclerosis. d-[113–122]apolipoprotein (apo) J (d-[113–122]apoJ) is a 10-residue peptide that is predicted to form a class G* amphipathic helix 6 from apoJ; it shows anti-inflammatory and anti-atherogenic properties. In the present study, we analyzed the effect of d-[113–122]apoJ in low-density lipoprotein receptor knockout mice(LDLR-KO) on the development of atherosclerosis and lipoprotein function. Fifteen-week-old female LDLR-KO mice fed an atherogenic Western-type diet were treated for eight weeks with d-[113–122]apoJ peptide, a scrambled peptide, or vehicle. Peptides were administered subcutaneously three days per week (200 µg in 100 µL of saline). After euthanasia, blood and hearts were collected and the aortic arch was analyzed for the presence of atherosclerotic lesions. Lipoproteins were isolated and their composition and functionality were studied. The extent of atherosclerotic lesions was 43% lower with d-[113–122]apoJ treatment than with the vehicle or scramble. The lipid profile was similar between groups, but the high-density lipoprotein (HDL) of d-[113–122]apoJ-treated mice had a higher antioxidant capacity and increased ability to promote cholesterol efflux than the control group. In addition, low-density lipoprotein (LDL) from d-[113–122]apoJ-treated mice was more resistant to induced aggregation and presented lower electronegativity than in mice treated with d-[113–122]apoJ. Our results demonstrate that the d-[113–122]apoJ peptide prevents the extent of atherosclerotic lesions, which could be partially explained by the improvement of lipoprotein functionality.