Reactive Oxygen Species and Hyaluronidase 2 Regulate Airway Epithelial Hyaluronan Fragmentation

Abstract

Hyaluronidase 2 (Hyal2) is a hyaluronan (HA)-degrading enzyme found intracellularly or/and anchored to the plasma membrane through glycosylphosphatidylinositol (GPI). Normal human bronchial epithelial cells (NHBE) grown at the air-liquid interphase (ALI), treated with PI-specific phospholipase C (PI-PLC), exhibited increased Hyal activity in secretions and decreased protein and activity on the apical membrane, confirming that GPI-anchored Hyal2 is expressed in NHBE cells and it remains active in its soluble form. We have reported that HA degradation was mediated by reactive oxygen species (ROS) in human airways. Here we show that ROS increase Hyal2 expression and activity in NHBE cells and that the p38MAPK signaling pathway is involved in this effect. Hyal2 induction was confirmed by using small interfering RNA (siRNA) expressing lentivirus. These in vitro findings correlated in vivo with smokers, where increased Hyal2 immunoreactivity in the epithelium was associated with augmented levels of HA and the appearance of low molecular mass HA species in bronchial secretions. In summary, this work provides evidence that ROS induce Hyal2, suggesting that Hyal2 is likely responsible for the sustained HA fragmentation in the airway lumen observed in inflammatory conditions associated with oxidative stress. Hyaluronan (HA)3 is a non-sulfated glycosaminoglycan found in the extracellular matrix, in body fluids, and in secretions of mammals. HA is synthesized by three transmembrane isoenzymes: HAS1, HAS2, and HAS3 at the inner face of the plasma membrane and translocated into the extracellular space (1).The association with various binding proteins (2, 3) confers HA with a unique plasticity to organize extracellular matrix (ECM) in a tissue specific fashion (for review see Ref. 4), varying from a tightly cross-linked mesh in cartilage to a highly hydrated matrix in dermis and vitreous humor (5).In addition, HA induces intracellular signaling by binding specific receptors at the cell surface, (6, 7) orchestrating a variety of host responses generally requiring an extensive deposition of a HA in the ECM. This deposition is essential for cumulus oophorus fertilization (8) as well as for proliferation and migration of mesenchymal cells. Airway smooth muscle cells exposed to polyinosinic acid-polycytidylic acid synthesize an abnormal HA matrix with cable-like structures that bind and retains leukocytes (9, 10), suggesting that HA play key roles on host defense against infections as well.Biological functions of HA are associated with its size (6, 11). For instance, high molecular weight HA (HMWHA) exhibit anti-angiogenic, anti-inflammatory, and immunosuppressive effects while small HA fragments are angiogenic and proinflammatory (12, 13). The contrasting responses elicited by different sizes of HA are exemplified in a recent report in which HMWHA attenuated while low molecular weight HA (LMWHA) increased ozone-induced airway hyperreactivity, in a mouse model of asthma (14).In human airway epithelium, HA is present at the lumen as...

Low Dose Ultraviolet B Irradiation Increases Hyaluronan Synthesis in Epidermal Keratinocytes via Sequential Induction of Hyaluronan Synthases Has1–3 Mediated by p38 and Ca2+/Calmodulin-dependent Protein Kinase II (CaMKII) Signaling*

“…The cause of this fragmentation, whether due to the Hyal enzymes or to non-enzymatic degradation via ROS (70) generated by the irradiation (71,72), remains unsettled at the moment. ROS may also have an indirect effect by activating Hyal enzymes (73,74), adding to the complex regulatory mechanisms.…”

Platelet hyaluronidase-2: an enzyme that translocates to the surface upon activation to function in extracellular matrix degradation

“…20 HA digestion can also occur by nonenzymatic mechanisms, mainly through reactive oxygen species. 21,22 We previously reported that mouse and human platelets and their megakaryocytic precursors express both HYAL2 messenger RNA and protein with no evidence for HYAL1. We also showed that platelets can degrade endothelial proinflammatory matrix HA into The online version of this article contains a data supplement.…”

Role of hyaluronan and hyaluronan-binding proteins in lung pathobiology

“…Unfortunately, the other hyaluronidase proteins were not examined in this study, but the authors speculate that the pH dependence of these enzymes could lead to different biological responses based on the production of different-sized HA fragments at the site of action. Extracellular acidosis is often observed in the airways of smokers and patients suffering from COPD and asthma (92). HA fragments are implicated in the progression of lung diseases (131).…”