Intratracheal instillation of pravastatin for the treatment of murine allergic asthma: a lung-targeted approach to deliver statins

Abstract

Systemic treatment with statins mitigates allergic airway inflammation, TH2 cytokine production, epithelial mucus production, and airway hyperreactivity (AHR) in murine models of asthma. We hypothesized that pravastatin delivered intratracheally would be quantifiable in lung tissues using mass spectrometry, achieve high drug concentrations in the lung with minimal systemic absorption, and mitigate airway inflammation and structural changes induced by ovalbumin. Male BALB/c mice were sensitized to ovalbumin (OVA) over 4 weeks, then exposed to 1% OVA aerosol or filtered air (FA) over 2 weeks. Mice received intratracheal instillations of pravastatin before and after each OVA exposure (30 mg/kg). Ultra performance liquid chromatography – mass spectrometry was used to quantify plasma, lung, and bronchoalveolar lavage fluid (BALF) pravastatin concentration. Pravastatin was quantifiable in mouse plasma, lung tissue, and BALF (BALF > lung > plasma for OVA and FA groups). At these concentrations pravastatin inhibited airway goblet cell hyperplasia/metaplasia, and reduced BALF levels of cytokines TNFα and KC, but did not reduce BALF total leukocyte or eosinophil cell counts. While pravastatin did not mitigate AHR, it did inhibit airway hypersensitivity (AHS). In this proof-of-principle study, using novel mass spectrometry methods we show that pravastatin is quantifiable in tissues, achieves high levels in mouse lungs with minimal systemic absorption, and mitigates some pathological features of allergic asthma. Inhaled pravastatin may be beneficial for the treatment of asthma by having direct airway effects independent of a potent anti-inflammatory effect. Statins with greater lipophilicity may achieve better anti-inflammatory effects warranting further research.

Innovations in asthma therapy: is there a role for inhaled statins?

“…This conversion likely occurs in the lungs and airways because many of the metabolizing enzymes present in the liver and gut are also present in the lungs, but at much lower concentration. Based on the anti-inflammatory and bronchodilatory effects of intra-tracheally delivered or inhaled statins in animal models, as well as on in vitro tracheal epithelial cells, we speculate that lung airway cells contain the enzymes necessary to activate statins [34,100,103,104]. This hypothesis is further corroborated by our recent PK and pharmacodynamic (PD) study of inhaled simvastatin in a nonhuman primate model.…”

“…Since the lung is the target organ of interest, it is vital to know if statins are reaching the lungs and airways. Mass spectrometry can be utilized to quantify statin levels and statin metabolites in plasma, and in the airway epithelium and bronchoalveolar lavage fluid [100–102]. Having this information combined with outcome-driven clinical data in asthma will help investigators determine the most effective route of administration: oral versus inhaled.…”

“…Hydrophilic statins like pravastatin or rosuvastatin typically require selective membrane transporters, i.e. the organic anion transporting polypeptide (OATP), to reach extrahepatic tissues [65,100]. However, lipophilic statins like simvastatin, readily diffuse across cell plasma membranes and do not require active transporters.…”

“…Effective methods employ liquid chromatography-tandem mass spectrometry (LC-MS/MS) for accurate quantification and high sensitivity detection [100–102,113,121]. The handling of samples for targeted analyses requires proper care to avoid drug metabolism post-harvest and to minimize conversion between the lactone (inactive pro-drug) and acid (active) forms of the statins, which is sensitive to temperature and pH.…”

“…Given the present uncertainty regarding the use of statins in asthma, we and others began investigating the safety and efficacy of delivering statins via inhalation in animal models, as an alternative approach to orally administered statins [100–102,104,105,128–130]. We are currently designing studies using mass spectrometry to measure concentrations of statins and their active metabolites in the plasma, airways, and lungs of patients ingesting oral statins.…”