PTP1B regulates metabolic reprogramming, inflammation and paracrine signalling in hypoxic macrophages: Implications for atherosclerotic plaque progression

https://doi.org/10.1007/s00392-025-02625-4

Mariel Schwietzer (Münster)1, X. Hu (Münster)1, W. Wang (Münster)1, M. Dorenkamp (Münster)1, D. Semo (Münster)1, R. Heller (Jena)2, H. Reinecke (Münster)1, R. Godfrey (Münster)1

1Universitätsklinikum Münster Klinik für Kardiologie I: Koronare Herzkrankheit, Herzinsuffizienz und Angiologie Münster, Deutschland; 2Institut für Molekulare Zellbiologie/Universitätsklinikum Jena Zentrum für Medizinische Biochemie Jena, Deutschland

 



Introduction:
Dysregulation of protein-tyrosine phosphatases (PTPs) has been linked to various pathologies, including cardiovascular diseases. PTP1B regulates several metabolic pathways and has been implicated in the development of atherosclerosis. However, how PTP1B is able to regulate atherosclerosis through the regulation of cellular metabolism and inflammation is poorly understood. Hypoxic macrophages are major contributors to the development and progression of atherosclerosis. Therefore, we aim to understand the pathways by which PTP1B can regulate metabolism in macrophages under hypoxic conditions. 

Methods: Primary human monocyte-derived macrophages are either transfected with siControl or siPTP1B or subjected to nucleofection with a control or PTP1B overexpression plasmid. Cells were maintained under normoxic (21% O2) or hypoxic (1% O2) conditions for 24 hours. We used qPCR, Western blot and ELISA to assess the expression levels of relevant target genes and proteins. For angiogenesis assays, HUVEC-based spheroids are exposed to hypoxic macrophage supernatants and analysed by light microscopy. 

Results: Our findings indicate that PTP1B function is significantly impaired in hypoxic macrophages, with its enzymatic activity compromised by 50-60% and expression suppressed by 30-40% (p=0.003). We identified several HIF1α target genes that are regulated by PTP1B. They showed decreased expression upon PTP1B knockdown (KD) and increased levels upon overexpression under hypoxic conditions, showing that PTP1B potentiates HIF1α effects. These genes include ENO2, PKFP, PK 1/2, BiP, GPI and ACO2. Notably, the absence of PTP1B correlates with a dramatic increase in VEGF release, reaching levels up to 3.5 times higher than baseline (p=0.0002). In contrast, PTP1B overexpression reduces VEGF secretion in response to hypoxia (p=0.008), suggesting a critical role for  PTP1B in mediating the interaction between plaque macrophages and endothelial cells. Angiogenesis assays further supported these observations, showing that O2 deprivation almost doubled endothelial cell sprouting when PTP1B levels were reduced (p=0.038). In addition, KD of PTP1B suppressed hypoxia-induced LDHA expression (p=0.0004), suggesting that PTP1B facilitates a metabolic shift in macrophages, while its overexpression increases LDHA levels (p=0.088). Moreover, PTP1B is known to be a major negative modulator of the insulin signalling cascade. We show that PTP1B KD attenuated insulin-induced inflammation in macrophages as evidenced by increased levels of pro-inflammatory cytokines such as TNF-alpha, IL-6, IL-8, IL-1B, and MCP-1. PTP1B thus influences the inflammatory process and growth of atherosclerotic plaques.

Conclusions: Together, these results highlight the central role of PTP1B in macrophage metabolism, inflammation and the paracrine signalling that influences angiogenesis in a hypoxic environment. Notably, PTP1B inhibition has potential anti-atherosclerotic properties. Our findings suggest that the inactivation of PTP1B in hypoxic macrophages alters their metabolic state and enhances neoangiogenesis, contributing to plaque progression. These data provide critical insights into the therapeutic potential of PTP1B in cardiovascular diseases.

 

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