Reduced SOX17 in HPAECs drives CXCL10/11 upregulation and CXCR3-dependant lymphocyte migration in vitro

<bold>Introduction.</bold> Pulmonary arterial hypertension (PAH) is a fatal disease characterized by occlusive pulmonary vascular remodelling, linked in part, to abnormal NF-κB signalling, with dysregulated chemokine expression (eg CXCL10) and, consequently, lesional leukocyte recruitment. Emerging data suggests that rare pathogenic mutations in the SOX17 gene and common genetic variants in the enhancer region may predispose to PAH, although the mechanisms are poorly defined. We have previously identified that SOX17-deficient HPAECs upregulate the chemokines CXCL10 and CXCL11. Here, we examined whether SOX17-knockdown HPAECs induce lymphocyte migration in vitro, via the receptors for CXCL10/11 (CXCR3) and whether abnormal NF-κB p65 activity underlies their regulation. <bold>Methods.</bold> HPAECs were transfected with siRNA against SOX17 (siSOX17), RELA (siRELA), siSOX17 + siRELA, or with control sequences (siControl). CXCL10 and CXCL11 mRNA were measured in siSOX17 HPAEC lysates (RT-qPCR), soluble protein release in supernatants (ELISA) and NF-κB p65 activity in cell lysates (immunoblotting). Chemotaxis of L1.2 lymphocytes (transfected with CXCR3) in response to siControl/siSOX17 supernatants were assessed using a Boyden chamber assay, +/- CXCR3 antagonist, AMG-487. <bold>Results.</bold> siSOX17 knockdown upregulated CXCL10 and CXCL11 mRNA and protein (vs siControl), which was attenuated in siRELA + siSOX17 HPAECs. siSOX17 HPAECs exhibited significantly higher phospho-NF-κB p65 expression (vs siControl). SOX17 knockdown significantly induced L1.2 lymphocyte migration (vs siControl), abrogated in the presence of AMG-487. <bold>Conclusion.</bold> Enhanced lymphocyte migration may be a pathomechanism of PAH due to SOX17 loss.