PI3Kγδ inhibition suppresses key disease features in a rat model of asthma.

BACKGROUND: Two isoforms of Phosphoinositide 3-kinase (PI3K), p110γ and p110δ, are predominantly expressed in leukocytes and represent attractive therapeutic targets for the treatment of allergic asthma. The study aim was to assess the impact of administration of an inhaled PI3Kγδ inhibitor (AZD8154) in a rat model of asthma. METHODS: Firstly, we checked that the tool compound, AZD8154, inhibited rat PI3K γ & δ kinases using rat cell-based assays. Subsequently, a time-course study was conducted in a rat model of asthma to assess PI3K activity in the lung and how it is temporally associated with other key transcription pathways and asthma like features of the model. Finally, the impact on lung dosed AZD8154 on target engagement, pathway specificity, airway inflammation and lung function changes was assessed. RESULTS: Data showed that AZD8154 could inhibit rat PI3K γ & δ isoforms and, in a rat model of allergic asthma the PI3K pathway was activated in the lung. Intratracheal administration of AZD8154 caused a dose related suppression PI3K pathway activation (reduction in pAkt) and unlike after budesonide treatment, STAT and NF-κB pathways were not affected by AZD8154. The suppression of the PI3K pathway led to a marked inhibition of airway inflammation and reduction in changes in lung function. CONCLUSION: These data show that a dual PI3Kγδ inhibitor suppress key features of disease in a rat model of asthma to a similar degree as budesonide and indicate that dual PI3Kγδ inhibition may be an effective treatment for people suffering from allergic asthma.

Protein prenylation restrains innate immunity by inhibiting Rac1 effector interactions.

Rho family proteins are prenylated by geranylgeranyltransferase type I (GGTase-I), which normally target proteins to membranes for GTP-loading. However, conditional deletion of GGTase-I in mouse macrophages increases GTP-loading of Rho proteins, leading to enhanced inflammatory responses and severe rheumatoid arthritis. Here we show that heterozygous deletion of the Rho family gene Rac1, but not Rhoa and Cdc42, reverses inflammation and arthritis in GGTase-I-deficient mice. Non-prenylated Rac1 has a high affinity for the adaptor protein Ras GTPase-activating-like protein 1 (Iqgap1), which facilitates both GTP exchange and ubiquitination-mediated degradation of Rac1. Consistently, inactivating Iqgap1 normalizes Rac1 GTP-loading, and reduces inflammation and arthritis in GGTase-I-deficient mice, as well as prevents statins from increasing Rac1 GTP-loading and cytokine production in macrophages. We conclude that blocking prenylation stimulates Rac1 effector interactions and unleashes proinflammatory signaling. Our results thus suggest that prenylation normally restrains innate immune responses by preventing Rac1 effector interactions.

Massive parallel sequencing questions the pathogenic role of missense variants in dilated cardiomyopathy.

BACKGROUND: Germline genetic variants are an important cause of dilated cardiomyopathy (DCM). However, recent sequencing studies have revealed rare variants in DCM-associated genes also in individuals without known heart disease. In this study, we investigate variant prevalence and genotype-phenotype correlations in Swedish DCM patients, and compare their genetic variants to those detected in reference cohorts. METHODS AND RESULTS: We sequenced the coding regions of 41 DCM-associated genes in 176 unrelated patients with idiopathic DCM and found 102 protein-altering variants with an allele frequency of <0.04% in reference cohorts; the majority were missense variants not previously described in DCM. Fifty-five (31%) patients had one variant, and 24 (14%) patients had two or more variants in the analysed genes. Detection of genetic variants in any gene, and in LMNA, MYH7 or TTN alone, was associated with early onset disease and reduced transplant-free survival. As expected, nonsense and frameshift variants were more common in DCM patients than in healthy individuals of the reference cohort 1000 Genomes Europeans. Surprisingly however, the prevalence, conservation and pathogenicity scores, and localization of missense variants were similar in DCM patients and healthy reference individuals. CONCLUSION: To our knowledge, this is the first study to identify correlations between genotype and prognosis when sequencing a large number of genes in unselected DCM patients. The similar distribution of missense variants in DCM patients and healthy reference individuals questions the pathogenic role of many variants, and suggests that results from genetic testing of DCM patients should be interpreted with caution.