Hyaluronan activates Hyal-2/WWOX/Smad4 signaling and causes bubbling cell death when the signaling complex is overexpressed.

Malignant cancer cells frequently secrete significant amounts of transforming growth factor beta (TGF-ß), hyaluronan (HA) and hyaluronidases to facilitate metastasizing to target organs. In a non-canonical signaling, TGF-ß binds membrane hyaluronidase Hyal-2 for recruiting tumor suppressors WWOX and Smad4, and the resulting Hyal-2/WWOX/Smad4 complex is accumulated in the nucleus to enhance SMAD-promoter dependent transcriptional activity. Yeast two-hybrid analysis showed that WWOX acts as a bridge to bind both Hyal-2 and Smad4. When WWOX-expressing cells were stimulated with high molecular weight HA, an increased formation of endogenous Hyal-2/WWOX/Smad4 complex occurred rapidly, followed by relocating to the nuclei in 20-40 min. In WWOX-deficient cells, HA failed to induce Smad2/3/4 relocation to the nucleus. To prove the signaling event, we designed a real time tri-molecular FRET analysis and revealed that HA induces the signaling pathway from ectopic Smad4 to WWOX and finally to p53, as well as from Smad4 to Hyal-2 and then to WWOX. An increased binding of the Smad4/Hyal-2/WWOX complex occurs with time in the nucleus that leads to bubbling cell death. In contrast, HA increases the binding of Smad4/WWOX/p53, which causes membrane blebbing but without cell death. In traumatic brain injury-induced neuronal death, the Hyal-2/WWOX complex was accumulated in the apoptotic nuclei of neurons in the rat brains in 24 hr post injury, as determined by immunoelectron microscopy. Together, HA activates the Hyal-2/WWOX/Smad4 signaling and causes bubbling cell death when the signaling complex is overexpressed.

Lung hyaluronan levels are decreased in alpha-1 antiprotease deficiency COPD.

INTRODUCTION: Hyaluronan (HA), a long-chain polysaccharide, is currently being evaluated as a potential therapeutic agent for pulmonary emphysema, based on previous studies from this laboratory indicating its protective effect against elastic fiber breakdown. To determine whether exogenously administered HA might replace a loss of this extracellular matrix component in this disease, we measured the content of HA in lung biopsies from both healthy individuals and alpha-1 antiprotease-deficient (AAPD) COPD patients with pulmonary emphysema. METHODS: Tissue samples (9 from COPD patients, 5 from controls) were digested with papain to isolate glycosaminoglycans, and lung HA was quantified with an enzyme-linked immunoabsorbent assay. RESULTS: HA was significantly decreased in the AAPDCOPD population compared to normal individuals (13.5 vs 21.7 ng/mg wet lung; p < 0.01). Furthermore, there was a positive correlation between HA levels and the following parameters: 1) percent predicted FEV1 (r = 0.78; p < 0.001), 2) percent predicted DLCO (r = 0.74; p < 0.05), and 3) serum levels of AAP (r = 0.61; p < 0.05). CONCLUSIONS: These findings support the hypothesis that depletion of lung HA plays a role in the pathogenesis of pulmonary emphysema, and that replacement of this matrix component could slow the progression of the disease.