Disruption of the gut microbiota promotes chronic inflammation in JAK2V617F-driven MPN: Evidence from mouse and human studies

Abstract Elevated levels of pro-inflammatory cytokines are linked to increased thrombotic risk and disease progression in myeloproliferative neoplasms (MPNs) patients. While persistent inflammation in MPN is multifactorial, a key driver is the presence of JAK2V617F mutation, which promotes the expansion of pro-inflammatory cells—such as monocytes and megakaryocytes—leading to abnormal cytokine production. Gut microbiota play a key role in regulating systemic inflammation, and the gut–immune axis appears disrupted in MPN patients. MPN patients experience dysbiosis–an imbalance in microbial composition (Eickhardt-Dalboge CS, Microbiol Spectr, 2024), and are 40% more likely to have a history of inflammatory bowel disease, indicating increased intestinal barrier vulnerability (Bak M, Cancers, 2020). Splanchnic vein thrombosis (SVT) is significantly more common in MPN patients (Liu A, Cancers, 2022), suggesting that potentially bacterial signals translocate to the liver and contribute to thrombosis. We hypothesize that dysbiosis and weakened gut barrier are contributing factors to systemic inflammation and thrombotic complications in MPN. In JAK2V617Fmice, dysbiosis is confirmed with elevated Firmicutes and Actinobacteria, two common gram-positive bacterial phyla, compared to wild-type (WT) control mice. Intestinal morphology is also altered in JAK2V617Fmice with increased thrombotic events (P=0.005) and leukocyte infiltration (P<0.0001) in the small intestine compared to WT controls. Addition of dextran sodium sulfate (DSS) (2% in drinking water), a widely used reagent for creating animal models of inflammatory bowel disease to JAK2V617Fmice compared to WT mice, led to rapid weight loss (P=0.006) and a significant increase in mortality rate (P=0.02), demonstrating JAK2V617Fmice are more vulnerable to intestinal damage. Vancomycin targets gram-positive bacteria, which are enriched in the guts of JAK2V617Fmice. Treatment with vancomycin (1 g/L in drinking water for 12 weeks) led to decreased circulating WBCs, reduced circulating monocytes, and decreased megakaryocyte numbers in the spleen and bone marrow (BM). The transcript levels of TGFβ, a pivotal player in MPN pathobiology, were lower in BM and liver of JAK2V617Fmice after vancomycin treatment. These data demonstrated downregulation of inflammatory signatures in JAK2V617Fmice after antibiotic treatment. Cardiac hypertrophy has been previously identified in JAK2V617Fmice (Shi K., J Hematol Oncol, 2014). Our data demonstrated that vancomycin treatment significantly reduced the heart weight (P=0.004) and left ventricular wall thickness (P=0.04) as compared to untreated JAK2V617F mice. The transcript levels of adhesion molecule VCAM-1 were decreased in both the liver and BM following vancomycin treatment. Together, these data demonstrate that microbiota depletion alleviates cardiovascular pathology and reduces the thrombotic risk. To validate these observations, we measured levels of lipopolysaccharide-binding protein (LBP)—a surrogate marker for microbial translocation in the serum from the peripheral and mesenteric blood of MPN patients who had experienced SVT (N=6). The levels of LBP were increased in both peripheral (P=0.048) and mesenteric blood samples (P=0.045) compared to healthy controls, suggesting that increased microbial translocation is positively associated with the development of SVTs in MPN patients. Our findings support a model where gut dysbiosis and impaired intestinal barrier function contribute to systemic inflammation in MPN through enhanced microbial translocation. In JAK2V617Fmice, microbiota depletion reduced pro-inflammatory cell populations and decreased cardiovascular pathology, demonstrating a previously underappreciated role for the gut microbiota in MPN pathogenesis. These data provide compelling proof-of-concept that targeting the microbiome-inflammation axis offers a new direction to dampen chronic inflammation in MPN patients. While long-term antibiotic use is not a viable clinical strategy, these results highlight the potential of other cost-effective microbiome-targeted approaches–such as probiotics, dietary modulation–as adjunctive therapies. By shifting focus to modulation of inflammation through gut health, this work opens a new translational path for improving outcomes in MPN.