Immunoglobulin A (IgA)-albumin complexes may be associated with pathophysiology of multiple myeloma, although the etiology is not clear. Detailed structural analyses of these protein–protein complexes may contribute to our understanding of the pathophysiology of this disease. We analyzed the structure of the IgA-albumin complex using various electrophoresis, mass spectrometry, and in silico techniques. The data based on the electrophoresis and mass spectrometry showed that IgA in the sera of patients was dimeric, linked via the J chain. Only dimeric IgA can bind to albumin molecules leading to IgA-albumin complexes, although both monomeric and dimeric forms of IgA were present in the sera. Molecular interaction analyses in silico implied that dimeric IgA and albumin interacted not only via disulfide bond formation, but also via noncovalent bonds. Disulfide bonds were predicted between Cys34 of albumin and Cys311 of IgA, resulting in an oxidized form of albumin. Furthermore, complex formation prolongs the half-life of IgA molecules in the IgA-albumin complex, leading to excessive glycation of IgA molecules and affects the accumulation of IgA in serum. These findings may demonstrate why complications such as hyperviscosity syndrome occur more often in patients with IgA dimer producing multiple myeloma.

Far-infrared radiation (FIR) may influence vascular endothelial function, but its time-dependent molecular effects in adult arterial endothelial cells remain incompletely defined. We investigated FIR-induced responses in human femoral artery endothelial cells (HFAECs) using transcriptomic, proteomic, and phosphoproteomic analyses with three biological replicates per condition. Transcriptomic profiling 3 h after 30 min of FIR irradiation identified 424 differentially expressed genes (210 upregulated and 214 downregulated) among 16,081 genes, including endothelial-protective, nitric oxide-related, oxidative-stress, and heat-shock response genes. Proteomic analysis identified 13 differentially abundant proteins immediately after irradiation and 23, 75, and 61 proteins at 6, 12, and 24 h, respectively. These temporal changes involved mitogen-activated protein kinase kinase/extracellular signal-regulated kinase signaling, vascular maturation, cytoskeletal organization, cell polarity, calcium/nitric oxide regulation, and stress adaptation. Phosphoproteomic analysis identified 12, 10, and 53 phosphorylation-related changes at 6, 12, and 24 h, respectively, indicating progression from actin and adhesion remodeling to junctional reorganization, focal adhesion maturation, and mechanosensing. Network analysis identified caveolin-1, β-catenin, and lamin B1 as hubs in a Rho guanosine triphosphatase-related module. Collectively, FIR induced a coordinated endothelial adaptive molecular response in HFAECs; functional studies are required to determine whether these changes enhance vascular repair.