AI Article Synopsis

  • The study investigates how T follicular helper cells and the cytokine IL-21 contribute to hypoxia-induced pulmonary hypertension (HPH), a condition that can lead to serious heart problems.
  • Using mouse models, the research found that mice lacking IL-21 or with reduced T cells showed less severe pulmonary hypertension, suggesting that IL-21 plays a crucial role in the disease's progression.
  • The findings revealed that chronic exposure to hypoxia increases germinal center B cell activity and promotes a shift in macrophages towards a phenotype that exacerbates vascular remodeling, showcasing potential targets for future therapies.

Article Abstract

Background: Hypoxia-induced pulmonary hypertension (HPH) is a subgroup of type 3 pulmonary hypertension that may cause early right ventricular failure and eventual cardiac failure, which lacks potential therapeutic targets. Our previous research demonstrated that T follicular helper (T) cells that produce IL-21 were involved in HPH. However, the molecular mechanisms of T/IL-21-mediated pathogenesis of HPH have been elusive. Here we investigate the role of T cells and IL-21 in HPH.

Methods: Studies were performed in C57BL/6 mice or IL-21 knockout mice exposed to chronic hypoxia to induce PH, and examined by hemodynamics. Molecular and cellular studies were performed in mouse lung and pulmonary arterial smooth muscle cells (PASMCs). M2 signature gene (Fizz1), M1 signature genes (iNos, IL-12β and MMP9), GC B cell and its marker GL-7, caspase-1, M2 macrophages, T cells, Bcl-6 and IL-21 level were measured. Proliferation rate of PASMCs was measured by EdU. Pyroptosis was assessed using Hoechst 33,342/PI double fluorescent staining.

Results: In response to chronic hypoxia exposure-induced pulmonary hypertension, IL-21 mice or downregulation of T cells in WT mice developed blunted pulmonary hypertension, attenuated pulmonary vascular remodelling. Furthermore, chronic hypoxia exposure significantly increased the germinal center (GC) B cell responses, which were not present in IL-21 mice or downregulation of T cells in WT mice. Importantly, IL-21 promoted the polarization of primary alveolar macrophages toward the M2 phenotype. Consistently, significantly enhanced expression of M2 macrophage marker Fizz1 were detected in the bronchoalveolar lavage fluid of HPH mice. Moreover, alveolar macrophages that had been cultivated with IL-21 promoted PASMCs proliferation and pyroptosis in vitro, while a selective CX3CR1 antagonist, AZD8797 (AZD), significantly attenuated the proliferation and pyroptosis of the PASMCs. Finally, ECM1 knockdown promoted IL-2-STAT5 signaling and inhibited Bcl-6 signaling to inhibit T differentiation in HPH.

Conclusions: T/IL-21 axis amplified pulmonary vascular remodelling in HPH. This involved M2 macrophage polarization, PASMCs proliferation and pyroptosis. These data suggested that T/IL-21 axis may be a novel therapeutic target for the treatment of HPH.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC11619207PMC
http://dx.doi.org/10.1186/s12931-024-03058-9DOI Listing

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