Melemenidis, S. | Search bioRxiv

bioRxiv2021

Endogenous Retroviral Elements Generate Pathologic Neutrophils and Elastase Rich Exosomes in Pulmonary Arterial Hypertension

Neutrophil elastase (NE) is implicated in pulmonary arterial hypertension (PAH) but the role of neutrophils in the pathogenesis of PAH is unclear. Here we show that neutrophils from PAH vs. control subjects produce and release increased NE associated with enhanced extracellular trap formation. PAH neutrophils are highly adherent and show decreased migration consistent with increased vinculin, identified on proteomic analysis and previously linked to an antiviral response. This was substantiated by a transcriptomic interferon signature in PAH neutrophils and an increase in human endogenous retrovirus (HERV-K) envelope protein. NE and interferon genes are induced by HERV-K envelope and vinculin is increased by HERV-K dUTPase that is elevated in PAH plasma. Neutrophil exosomes from PAH plasma contain increased NE and HERV-K envelope and induce pulmonary hypertension in mice, that is mitigated by the NE inhibitor and antiviral agent, elafin. Thus, elevated HERVs explain pathological neutrophils linked to PAH induction and progression.

immunology↗

bioRxiv2020

Targeting C5aR1 Increases the Therapeutic Window of Radiotherapy

Engaging innate immune pathways is emerging as a productive way of achieving durable anti-tumor responses. However, systemic administration of these therapies can result in toxicity, deemed to be particularly problematic when combined with current standard-of-care cytotoxic treatments such as radiotherapy. Increasing the therapeutic window of radiotherapy may be achieved by using targeted therapies, however, few pre-clinical studies investigate both tumor and normal tissue responses in detail. Here we show that targeting innate immune receptor C5aR1 improves tumor radiation response while reducing radiation-induced normal tissue toxicity, thereby increasing the therapeutic window. Genetically or pharmacologically targeting C5aR1 increases both IL-10 expression in the small intestine and IL-10 secretion by tumor cells. Increased IL-10 attenuates RelA phosphorylation and increases apoptosis in tumor cells, leading to improved radiation responses in murine models. Of note, these radiosensitizing effects are tumor-specific since, in the gastrointestinal tract, targeting C5aR1 instead results in decreased crypt cell apoptosis reduced signs of histological damage and improved survival following total abdominal irradiation in mice. Furthermore, the potent and orally active C5aR1 inhibitor, PMX205, improves tumor radiation responses even in a context of reduced/absent CD8+ T cell infiltration. These data indicate that PMX205 can modulate cancer-cell intrinsic functions to potentiate anti-tumor radiation responses even in tumors displaying features of T-cell deficiency or exclusion. Finally, using a preclinical murine model allowing the simultaneous assessment of tumor and normal tissue radiation responses, we show that PMX205 treatment reduces histological and functional markers of small-bowel toxicity while affording a positive tumor response. Our data, therefore, suggest that targeting C5aR1 could be a promising approach for increasing the therapeutic window of radiotherapy.

cancer biology↗