Galectin-8 induces functional disease markers in human osteoarthritis and cooperates with galectins-1 and -3

Abstract

The reading of glycan-encoded signals by tissue lectins is considered a major route of the flow of biological information in many (patho)physiological processes. The arising challenge for current research is to proceed from work on a distinct protein to family-wide testing of lectin function. Having previously identified homodimeric galectin-1 and chimera-type galectin-3 as molecular switches in osteoarthritis progression, we here provide proof-of-principle evidence for an intra-network cooperation of galectins with three types of modular architecture. We show that the presence of tandem-repeat-type galectin-8 significantly correlated with cartilage degeneration and that it is secreted by osteoarthritic chondrocytes. Glycan-inhibitable surface binding of galectin-8 to these cells increased gene transcription and the secretion of functional disease markers. The natural variant galectin-8 (F19Y) was less active than the prevalent form. Genome-wide array analysis revealed induction of a pro-degradative/inflammatory gene signature, largely under control of NF-κB signaling. This signature overlapped with respective gene-expression patterns elicited by galectins-1 and -3, but also presented supplementary features. Functional assays with mixtures of galectins that mimic the pathophysiological status unveiled cooperation between the three galectins. Our findings shape the novel concept to consider individual galectins as part of a so far not realized teamwork in osteoarthritis pathogenesis, with relevance beyond this disease.Electronic supplementary materialThe online version of this article (10.1007/s00018-018-2856-2) contains supplementary material, which is available to authorized users.

Galectins‐1 and ‐3 in Human Intervertebral Disc Degeneration: Non‐Uniform Distribution Profiles and Activation of Disease Markers Involving NF‐κB by Galectin‐1

“…As illustrated by work in vitro, Gal‐1 was secreted by IVD cells, bound to their surface and proved active as elicitor of functional disease markers. In contrast, tested in parallel or as part of a mixture (at concentrations previously defined to be active for osteoarthritic chondrocytes), Gal‐3 failed to induce expression of relevant genes, thus revealing functional divergence between these two galectins. In agreement, Gal‐1's immunopositivity profile in serial sections did not consistently match Gal‐3 distribution, further arguing against a functional similarity as observed in osteoarthritic chondrocytes …”

“…Western blot analyses were performed as previously described . Briefly, membranes (nitrocellulose blotting membrane 0.2 µm; GE Healthcare Life Sciences, Freiburg, Germany) were incubated for 2 h with primary antibodies specific for phospho NF‐κB p65 (Ser536; 1:1,000; rabbit monoclonal; Cell Signaling, Danvers, MA), NF‐kB p65 (1:1,000; mouse monoclonal; Cell Signaling), and β‐actin (1:5,000; mouse monoclonal; Cell Signaling).…”

“…Western blot analyses were performed as previously described. 8 Briefly, membranes (nitrocellulose blotting membrane 0.2 µm; GE Healthcare Life Sciences, Freiburg, Germany) were incubated for 2 h with primary antibodies specific for phospho NF-κB p65 (Ser536; 1:1,000; rabbit monoclonal; Cell Signaling, Danvers, MA), NF-kB p65 (1:1,000; mouse monoclonal; Cell Signaling), and β-actin (1:5,000; mouse monoclonal; Cell Signaling). Thereafter, membranes were incubated for 1 h with a solution containing IRDye 800CW goat anti-rabbit IgG (1:15,000; LI-COR, Bad Homburg, Germany) and IRDye 680LT goat anti-mouse IgG (1:15,000; LI-COR, Bad Homburg, Germany).…”

“…Being hereby guided to look at tissue degeneration in osteoarthritis, we previously found that an emerging group of elicitors of functional disease markers in cartilage degeneration belongs to the class of endogenous lectins. In particular, we recently revealed the upregulation of distinct endogenous galectins in osteoarthritic cartilage and their involvement in triggering a pro‐degradative/‐inflammatory microenvironment via expression of nuclear factor‐kB (NF‐kB)‐regulated gene expression profiles . Mechanistically, tissue lectins “read” cellular signals encoded by glycans and translate their information into molecular activities .…”

“…In particular, we recently revealed the upregulation of distinct endogenous galectins in osteoarthritic cartilage 5 and their involvement in triggering a pro-degradative/-inflammatory microenvironment via expression of nuclear factor-kB (NF-kB)-regulated gene expression profiles. [6][7][8] Mechanistically, tissue lectins "read" cellular signals encoded by glycans and translate their information into molecular activities. 9,10 In osteoarthritis, members of the galectin family, that is, galectins-1, -3, and -8 (Gal-1, Gal-3, and Gal-8), serve as signalinginducing mediators (for a recent systematic literature review on galectins in (osteo)arthritis, see Salamanna et al 11 ).…”