Characterisation of tyrosine kinase inhibitor-receptor interactions at VEGFR2 using sunitinib-red and nanoBRET

Role of endothelin ETA receptors in the hypertension induced by the VEGFR-2 kinase inhibitors axitinib and lenvatinib in conscious freely-moving rats

Receptor tyrosine kinase inhibitors (RTKIs) suppress tumour growth by targeting vascular endothelial growth factor receptor 2 (VEGFR-2) which is an important mediator of angiogenesis. Here, we demonstrate that two potent RTKIs, axitinib and lenvatinib, are associated with hypertensive side effects. Doppler flowmetry was used to evaluate regional haemodynamic profiles of axitinib and lenvatinib. Male Sprague Dawley rats (350-500 g) were instrumented with Doppler flow probes (renal and mesenteric arteries and descending abdominal aorta) and catheters (jugular vein and distal abdominal aorta, via the caudal artery). Rats were dosed daily with axitinib (3 or 6 mg.kg-1) or lenvatinib (1 or 3 mg.kg-1) and regional haemodynamics were recorded over a maximum of 4 days. Both RTKIs caused significant (p < 0.05) increases in mean arterial pressure (MAP), which was accompanied by significant (p < 0.05) vasoconstriction in both the mesenteric and hindquarters vascular beds. To gain insight into the involvement of endothelin-1 (ET-1) in RTKI-mediated hypertension, we also monitored heart rate (HR) and MAP in response to axitinib or lenvatinib in animals treated with the ETA receptor selective antagonist sitaxentan (5 mg.kg-1) or the mixed ETA/ETB receptor antagonist bosentan (15 mg.kg-1) over two days. Co-treatment with bosentan or sitaxentan markedly reduced the MAP effects mediated by both RTKIs (p < 0.05). Bosentan, but not sitaxentan, also attenuated ET-1 mediated increases in HR. These data suggest that selective antagonists of ETA receptors may be appropriate to alleviate the hypertensive effects of axitinib and lenvatinib.

Transcriptome analyses reveal common immune system dysregulation in PAH patients and Kcnk3-deficient rats

Pulmonary arterial hypertension (PAH) is a severe disease caused by progressive distal pulmonary artery obstruction. One cause of PAH are loss-of-function mutations in the potassium channel subfamily K member 3 (KCNK3). KCNK3 encodes a two-pore domain potassium channel, which is crucial for pulmonary circulation homeostasis. However, our understanding of the pathophysiological mechanisms underlying KCNK3 dysfunction in PAH is still incomplete. Taking advantage of unique Kcnk3-deficient rats, we analyzed the transcriptomic changes in the lungs from homozygous Kcnk3-deficient rats and wild-type (WT) littermates and compared them to PAH patient transcriptomic data. Transcriptome analysis of lung tissue obtained from WT and Kcnk3-deficient rats identified 1915 down- or upregulated genes. In addition, despite limited similarities at the gene level, we found a strong common signature at the pathway level in PAH patients and Kcnk3-deficient rat lungs, especially for immune response. Using the dysregulated genes involved in the immune response, we identified Spleen Associated Tyrosine Kinase (SYK), a significantly downregulated gene in human PAH patients and Kcnk3-deficient rats, as a hub gene. Our data suggests that the altered immune system response observed in PAH patients may be partly explained by KCNK3 dysfunction through the alteration of SYK expression.