Prostaglandin E2 Regulates Neutrophil Survival Via EP2/PKA/NR4A2 Signalling in the Context of COPD

Chronic Obstructive Pulmonary Disease (COPD) is a neutrophil-associated pulmonary condition that is accompanied by chronic inflammation. Neutrophil lifespan is typically controlled by constitutive apoptosis, but their prolonged persistence at inflammatory sites is implicated in COPD pathology. However, current COPD therapies are inadequate at targeting neutrophilia. Prostaglandin E2 (PGE2) is a potent pro-survival mediator in neutrophils that is increased in COPD. Therefore, PGE2 may contribute to neutrophilic accumulation in COPD lungs and the resolution of inflammation may be achieved by decreasing neutrophil lifespan. Specifically, it was hypothesised that PGE2 modulates protein kinase A (PKA)-dependent neutrophil lifespan through a specific prostaglandin (EP) receptor subtype, and that the nuclear receptors NR4A2 or NR4A3 are downstream effectors of PKA-mediated neutrophil survival. Human polymorphonuclear neutrophils (PMN) were isolated from the blood of healthy volunteers and COPD patients. Cellular apoptosis was assessed by light microscopy and phosphatidyl serine exposure. Gene expression of PGE2 and NR4A receptors was measured by RT-PCR and qPCR. Additionally, a novel approach uses murine neutrophils (mNØ) derived from cultures of bone-marrow progenitors, conditionally immortalised by expression of a chimeric Hoxb8 protein. RNAi strategies to knock down NR4A2 and NR4A3 in mNØ were undertaken. PGE2 and a pharmacological EP2 receptor agonist induced PKA-dependent PMN survival and NR4A2 expression by qPCR. Likewise, PGE2-induced PKA survival was blocked by EP2 receptor antagonism. Interestingly, the inflammatory mediator LPS increased EP2 and EP4 expression by qPCR in healthy control and COPD PMN. Consistently, LPS induced early PKA-dependent survival and enhanced late PGE2 survival. Additionally, RNAi-mediated knockdown of NR4A2 in mNØ decreased cell numbers during mNØ differentiation. In conclusion, EP2 is the dominant receptor subtype in PGE2/PKA survival in PMN. In the context of COPD, LPS further enhances PGE2 survival through increased prostaglandin receptor expression. Moreover, this study links the nuclear receptor NR4A2 to neutrophil survival induced by the PGE2/PKA signalling axis, potentially providing a novel, specific molecular target for neutrophilia in COPD

Novel Advances in Modifying BMPR2 Signaling in PAH

Pulmonary Arterial Hypertension (PAH) is a disease of the pulmonary arteries, that is characterized by progressive narrowing of the pulmonary arterial lumen and increased pulmonary vascular resistance, ultimately leading to right ventricular dysfunction, heart failure and premature death. Current treatments mainly target pulmonary vasodilation and leave the progressive vascular remodeling unchecked resulting in persistent high morbidity and mortality in PAH even with treatment. Therefore, novel therapeutic strategies are urgently needed. Loss of function mutations of the Bone Morphogenetic Protein Receptor 2 (BMPR2) are the most common genetic factor in hereditary forms of PAH, suggesting that the BMPR2 pathway is fundamentally important in the pathogenesis. Dysfunctional BMPR2 signaling recapitulates the cellular abnormalities in PAH as well as the pathobiology in experimental pulmonary hypertension (PH). Approaches to restore BMPR2 signaling by increasing the expression of BMPR2 or its downstream signaling targets are currently actively explored as novel ways to prevent and improve experimental PH as well as PAH in patients. Here, we summarize existing as well as novel potential treatment strategies for PAH that activate the BMPR2 receptor pharmaceutically or genetically, increase the receptor availability at the cell surface, or reconstitute downstream BMPR2 signaling

Integrin Signaling Shaping BTK-Inhibitor Resistance

Integrins are adhesion molecules that function as anchors in retaining tumor cells in supportive tissues and facilitating metastasis. Beta1 integrins are known to contribute to cell adhesion-mediated drug resistance in cancer. Very late antigen-4 (VLA-4), a CD49d/CD29 heterodimer, is a beta1 integrin implicated in therapy resistance in both solid tumors and haematological malignancies such as chronic lymphocytic leukemia (CLL). A complex inside-out signaling mechanism activates VLA-4, which might include several therapeutic targets for CLL. Treatment regimens for this disease have recently shifted towards novel agents targeting BCR signaling. Bruton’s tyrosine kinase (BTK) is a component of B cell receptor signaling and BTK inhibitors such as ibrutinib are highly successful; however, their limitations include indefinite drug administration, the development of therapy resistance, and toxicities. VLA-4 might be activated independently of BTK, resulting in an ongoing interaction of CD49d-expressing leukemic cells with their surrounding tissue, which may reduce the success of therapy with BTK inhibitors and increases the need for alternative therapies. In this context, we discuss the inside-out signaling cascade culminating in VLA-4 activation, consider the advantages and disadvantages of BTK inhibitors in CLL and elucidate the mechanisms behind cell adhesion-mediated drug resistance

Multiple Mechanisms of NOTCH1 Activation in Chronic Lymphocytic Leukemia: NOTCH1 Mutations and Beyond

The Notch signaling pathway plays a fundamental role for the terminal differentiation of multiple cell types, including B and T lymphocytes. The Notch receptors are transmembrane proteins that, upon ligand engagement, undergo multiple processing steps that ultimately release their intracytoplasmic portion. The activated protein ultimately operates as a nuclear transcriptional co-factor, whose stability is finely regulated. The Notch pathway has gained growing attention in chronic lymphocytic leukemia (CLL) because of the high rate of somatic mutations of the NOTCH1 gene. In CLL, NOTCH1 mutations represent a validated prognostic marker and a potential predictive marker for anti-CD20-based therapies, as pathological alterations of the Notch pathway can provide significant growth and survival advantage to neoplastic clone. However, beside NOTCH1 mutation, other events have been demonstrated to perturb the Notch pathway, namely somatic mutations of upstream, or even apparently unrelated, proteins such as FBXW7, MED12, SPEN, SF3B1, as well as physiological signals from other pathways such as the B-cell receptor. Here we review these mechanisms of activation of the NOTCH1 pathway in the context of CLL; the resulting picture highlights how multiple different mechanisms, that might occur under specific genomic, phenotypic and microenvironmental contexts, ultimately result in the same search for proliferative and survival advantages (through activation of MYC), as well as immune escape and therapy evasion (from anti-CD20 biological therapies). Understanding the preferential strategies through which CLL cells hijack NOTCH1 signaling may present important clues for designing targeted treatment strategies for the management of CLL