Role of Soluble [alpha]-Klotho in the Alleviation of Acute Lung Injury

Inhalational insults like smoke, toxic fumes, and particulate matter plague our modern environment. These insults can cause acute lung injury (ALI), a syndrome characterized by inflammation, increased permeability, and pulmonary infiltrates. Moderate ALI causes hypoxemia, leading to respiratory failure if left unattended. Patients with severe ALI develop acute respiratory distress syndrome and require supplemental oxygen or mechanical ventilation. Despite advances in critical care, mortality from ALI is 40%, and there is an urgent need for a solution. Soluble alpha-Klotho (herein termed Klotho) is a pleiotropic protein essential for tissue maintenance and protection. Transmembrane Klotho is synthesized mainly in the kidney and cleaved at the transmembrane site of renal tubules for circulation to extra-renal organs. The lung does not produce endogenous Klotho but relies on the protein delivered via venous blood return. Klotho-deficient mice lungs have higher oxidative stress, higher antioxidant demand, and varying airspace size and distribution. Systemically, Klotho-deficient mice develop premature organ degeneration and have a shorter lifespan than wild-type (WT) mice. However, constitutive overexpression of Klotho in transgenic-Klotho (Tg-Kl) mice improves longevity and reduces oxidative stress. Based on these findings, I tested the hypothesis that Klotho could act as a therapeutic to reduce inflammation and oxidative stress caused by ALI. First, to characterize Klotho actions in the lung, Tg-Kl mice were subjected to two experimental injury models, cigarette smoke or hyperoxia. Mouse bronchoalveolar lavage fluid (BALF) was assayed for oxidative damage to compare age, genotype, and exposure; fixed lungs were sectioned, stained, and the morphology examined. Next, exogenous Klotho was incorporated into poly-lactic-co-glycolic-acid (PLGA) nanoparticles (NPs), a vehicle chosen for its desired properties suitable for inhalational delivery. Klotho-containing PLGA NPs were characterized for inhalational delivery and screened in A549 cells exposed to cigarette smoke. WT or Klotho-insufficient (Kl/+) mice inhaled Klotho-containing NPs following exposure to hyperoxia-recovery. Inhalational studies used the same biomarker panel and morphology previously mentioned to assess outcomes. The experiments demonstrated that increased endogenous Klotho in Tg-Kl mice attenuated hyperoxia-induced oxidative damage, reduced inflammation, and prevented mortality. In addition, Klotho NPs prevented cytotoxicity and DNA damage in smoke-exposed A549 cells. Finally, Klotho cDNA NP-treated mice showed preserved lung morphology and reduced oxidative damage and mortality rates compared to vector-treated mice. These studies showed that Klotho exerts cytoprotective functions in the lung, alleviating ALI and further damage in the mouse model, and could therefore have clinically therapeutic potential.

Author dc:creator

• Gagan, Joshuah Marian

Contributors dc:contributor

• Petroll, W. Matthew
• Terada, Lance
• Lux, Jacques
• Hsia, Connie C.W.
• Miller, R. Tyler

• Acute Lung Injury
• Glucuronidase
• Klotho Proteins
• Lung
• Oxidative Stress

Language dc:language

en

Identifier

1522122349

OAI identifier oai:identifier

oai:utswmed-ir.tdl.org:2152.5/10594