title: α-Klotho protects against oxidative damage in pulmonary epithelia.
abstract: α-Klotho exerts pleiotropic biological actions. Heterozygous α-Klotho haplo-insufficient mice (kl/+) appear normal at baseline except for age-related changes in the lung, suggesting heightened pulmonary susceptibility to α-Klotho deficiency. We used in vivo and in vitro models to test whether α-Klotho protects lung epithelia against injury. Normally, α-Klotho is not expressed in the lung, but circulating α-Klotho levels are reduced -40% in kl/+ mice and undetectable in homozygous α-Klotho-deficient mice (kl/kl). kl/+ mice show distal air space enlargement at a given airway pressure, with elevated lung oxidative damage marker (8-hydroxydeoxyguanosine; 8-OHdG); these abnormalities are exacerbated in kl/kl mice. Studies were performed in A549 lung epithelial cells and/or primary culture of alveolar epithelial cells. Hyperoxia (95% O2) and high inorganic phosphate concentrations (Pi, 3-5 mM) additively caused cell injury (lactate dehydrogenase release), oxidative DNA damage (8-OHdG), lipid oxidation (8-isoprostane), protein oxidation (carbonyl), and apoptosis (caspase-8 activity and TUNEL stain). Transfection of transmembrane or soluble α-Klotho, or addition of soluble α-Klotho-containing conditioned media, increased cellular antioxidant capacity (Cu- and Fe-based assays) via increased nuclear factor erythroid-derived 2-related factors 1 and 2 (Nrf1/2) transcriptional activity and ameliorated hyperoxic and phosphotoxic injury. To validate the findings in vivo, we injected α-Klotho-containing conditioned media into rat peritoneum before and during hyperoxia exposure and found reduced alveolar interstitial edema and oxidative damage. We conclude that circulating α-Klotho protects the lung against oxidative damage and apoptosis partly via increasing endogenous antioxidative capacity in pulmonary epithelia. Cytoprotection by α-Klotho may play an important role in degenerative diseases of the lung.
authors: Departments of Internal Medicine, Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas.
authors: Priya
authors: P
authors: Ravikumar
authors: Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas.
authors: Jianfeng
authors: J
authors: Ye
authors: Departments of Internal Medicine.
authors: Jianning
authors: J
authors: Zhang
authors: Departments of Internal Medicine.
authors: Sydney N
authors: SN
authors: Pinch
authors: Departments of Internal Medicine, Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas.
authors: Ming Chang
authors: MC
authors: Hu
authors: Pathology, Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas.
authors: Makoto
authors: M
authors: Kuro-o
authors: Departments of Internal Medicine.
authors: Connie C W
authors: CC
authors: Hsia
authors: Departments of Internal Medicine, Physiology, and Charles and Jane Pak Center of Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas orson.moe@UTSouthwestern.edu.
authors: Orson W
authors: OW
authors: Moe
mesh_terms: D000818:Animals; D061745:Antioxidant Response Elements; D017209:Apoptosis; D045744:Cell Line, Tumor; D004249:DNA Damage; D015870:Gene Expression; D005786:Gene Expression Regulation; D005966:Glucuronidase / Q000502:physiology*; D006801:Humans; D000090265:Klotho Proteins; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008822:Mice, Transgenic; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism; D050050:Protein Carbonylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D020545:Respiratory Mucosa / Q000378:metabolism* / Q000473:pathology
chemical_list: D005966:Glucuronidase; D000090265:Klotho Proteins; D010100:Oxygen
keywords: Klotho cytoprotection; alveolar epithelial cells; antioxidant capacity; hyperoxia; lung injury; phosphate toxicity