Impact de l’aphérèse des lipoprotéines

Formation impact de l’aphérèse des lipoprotéines, tutoriel & guide de travaux pratiques en pdf.

Materials and methods

Materials and methods are detailed in the Supporting Information. Briefly, nine HoFH subjects underwent one complete LA treatment using DSA (Liposorber® LA-15 system, Kaneka Corporation, Osaka, Japan) as part of their routine bi-monthly therapy. Blood samples were collected immediately pre- and post-LA. Microarray analyses were performed using GeneChip® Human Gene 2.0 ST Array (Affymetrix, Santa Clara, CA, USA) to assess the whole blood expression of >30 000 annotated genes involved in various metabolic pathways, including the cardiovascular system. Genes that whole blood expression was significantly modified post vs pre-LA with DSA were subsequently submitted to Ingenuity Pathway Analysis system (Ingenuity® software, www.ingenuity.com) to identify associated metabolic pathways.

Results

The median filtrated plasma volume during LA with DSA was 4400 mL (range: 3000-4900). LA with DSA significantly decreased LDL-C and lipoprotein (a) (Lp(a)) concentrations (Table 1). LA had no impact on the whole blood mRNA expression of most genes associated with cardiovascular health, including key genes involved in cholesterol, fatty acid and lipoprotein metabolism (hydroxymethylglutaryl-CoA reductase, microsomal triglyceride transfer protein, LDLR, VLDL receptor, sterol regulatory binding protein 1 and 2 and peroxisome proliferator-activated receptors). However, as presented in Figure 1, LA with DSA significantly upregulated the whole blood expression of early growth response protein (EGR)1, EGR3 and B-cell lymphoma 3-encoded protein (BCL3), while a statistical trend suggested an upregulation in the expression of the matrix metallopeptidase 9 (MMP9) (P0.09). These 4 genes were associated with 28 overrepresented pathways. Of those, 3 were associated to BCL3, 5 to EGR1, 19 to MMP9 and 1 to EGR1 and MMP9 (Supporting Information table 1). Most pathways were related to endothelial activation or inflammation.

Discussion and conclusion

This study revealed that a single LA treatment using DSA had no impact on the whole blood expression of most genes associated with cardiovascular health, including those involved in cholesterol, fatty acid and lipoprotein metabolism, in patients with HoFH. These observations are consistent with the neutral impact of LA therapy on the secretion and clearance of apoB-containing particles as previously reported.4 Accumulating evidence now suggests that LA therapy does not induce alterations in lipoprotein metabolism or a metabolic response to counterbalance the acute depletion of circulating lipoproteins. These observations suggest that the cardioprotective effects of LA therapy in HoFH patients are mainly related to the repetitive mechanical extracorporeal removal of cholesterol-rich apoB-particles from plasma rather than intravascular mechanisms induced by the therapy.
EGR1 and EGR3 are involved in inflammation and endothelial dysfunction.5, 6 BCL3 is also involved in inflammation as a member of the nuclear factor-kappa-B family,7 and MMP9 is implicated in intimal thickening and plaque rupture.8 Identified overrepresented pathways associated with these genes are also concordant with the function of these genes. Our results suggest that contact between the blood cells and the primary membrane or extracorporeal circulation could upregulate the expression of EGR1, EGR3, BCL3 and MMP9 in blood cells. Alternatively, it could not be excluded that the upregulation of these genes reflect acute endothelial activation, since gene expression assessment using peripheral blood is a valid marker of endothelium homeostasis.9 This hypothesis is also concordant with a previous observation that elevations in plasma concentrations of interleukin-6, a cytokine that can be secreted from endothelial cells, were reported following LA with DSA in HoFH patients.10, 11
In the present study, it remains uncertain whether the upregulation in the expression of EGR1, EGR3, BCL3 and MMP9 was related to the DSA system or to the LA treatment per se. This effect was unlikely attributable to dextran-sulfate, as whole blood cells and plasma are separated in the LA system prior to the adsorption step. It also remains unlikely that the changes we observed were related to the acute reduction in plasma lipids induced by LA with DSA. Moreover, it remains uncertain whether the expression of these genes increased or decreased in the days following LA. Nenseter et al.12 previously compared serum levels and expression from peripheral blood mononuclear cells of MMP9 measured the day before LA and 15 days after LA in HoFH subjects and no difference was observed. In this context, in the present study, one can assume that the activation of the genes observed was attenuated in the days following the treatment. Further investigation is required.
In conclusion, this study demonstrated that a single LA treatment with DSA has very limited impact on the expression of a broad spectrum of genes associated with cardiovascular health. The results suggest that LA with DSA does not perturb overall patterns of gene expression. The results also suggest that contact between blood cells and the primary membrane or extracorporeal circulation could upregulate the expression of EGR1, EGR3, BCL3 and MMP9 in blood cells. Molecular mechanisms underlying the upregulation of EGR1, EGR3, BCL3 and MMP9 mRNA expression in whole blood remain to be identified.

Acknowledgments

The authors are grateful for the collaboration of the subjects and for the dedicated staff of the Lipid Research Center. All of the authors read and approved the final manuscript.
Authors’ contributions and disclosures
PC and BL designed the research; JPDC, NL, and AJT conducted the research; JPDC, PC, and AJT analyzed the data; JPDC, AJT, JB, BL, and PC wrote the paper; and PC had primary responsibility for the final content. JPDC is the recipient of doctoral scholarships from the Canadian Institute of Health Research and the Fonds de Recherche du Québec – Santé. BL is the Chair of Nutrition at Laval University. This work was supported by an unrestricted grant from Kaneka Pharma LLC (Osaka, Japan).
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