Role and mechanism of NLRC3 in hypoxic pulmonary hypertension

AIM To investigate the role and underlying mechanism of NLRC3 in modulating hypoxic pulmonary hypertension (HPH) through immune regulation.

METHODS Wild-type (WT) and NLRC3 knockout (NLRC3^−/−) mice were randomly divided into four groups: control, NLRC3^−/−, hypoxia, and hypoxia+NLRC3^−/−. Mice in the hypoxia and hypoxia+NLRC3^−/− groups were exposed to hypobaric hypoxia for 6 weeks, while those in the control and NLRC3^−/− groups were maintained in normobaric normoxia. Pulmonary vascular remodeling, right ventricular pressure (RVSP), right ventricular hypertrophy index (RVHI), NLRC3 expression, inflammatory cytokine levels, and NF-κB signaling activation were evaluated. Cultivate wild-type and NLRC3^−/−mouse primary bone marrow mesenchymal cells (BMDMs), induce them with macrophage colony-stimulating factor (M-CSF), and divide them into control group, NLRC3^−/− group, hypoxia group, and Hypoxia+NLRC3^−/− group. The Hypoxia group and Hypoxia+NLRC3^−/−group were stimulated in a low oxygen incubator for 24 or 48 hours, while the Control group and NLRC3^−/− group were placed in a normoxic incubator. Detect NLRC3, inflammatory cytokine expression, and NF - κ B signaling activation levels in each group.

RESULTS Compared with the Control group, the expression of NLRC3 in lung tissue and BMDMs in the Hypoxia group decreased (P<0.01), and the ratio of vascular wall thickness (WT%), vascular wall area ratio (WA%), right ventricular systolic pressure (RVSP), right ventricular hypertrophy index (RVHI) increased (P<0.01), and α-SMA positive cells increased; The expression of IL-1β and IL-18 in lung tissue increased (P<0.05) and the ratio of p-p65/p65 increased (P<0.01); The expression of IL-1β, IL-18 and the ratio of p-p65/p65 in BMDMs increased (P<0.01). Compared with NLRC3^−/− group, WT%, WA%, RVSP, RVHI and α-SMA positive cells were increased in Hypoxia+NLRC3^−/−group (P<0.01); The expression of IL-1β, IL-18 and the ratio of p-p65/p65 in lung tissue and BMDMs increased (P<0.01). Compared with the Hypoxia group, WT%, WA%, RVSP and RVHI in the Hypoxia+NLRC3^−/−group increased (P<0.01), and α-SMA positive cells increased; The expression of IL-1β, IL-18 and p-p65/p65 ratio in lung tissue increased (P<0.01); The expression of IL-1β and IL-18 in BMDMs increased (P<0.01), and the ratio of p-p65/p65 increased (P<0.05).

CONCLUSION  NLRC3 negatively regulates NF-κB signaling activation in macrophages of mice with HPH, thereby inhibiting the inflammatory response.