Impact of innate immune memory on MDS progression by TET2-driven inflammation Free

Myelodysplastic syndrome (MDS) is a clonal, age-related bone marrow failure disorder. Mutations in the epigenetic regulator, TET2, drive disease in 30% of MDS patients. However, some individuals with no hematopoietic disorder harbor mutations and have low probability of disease progression, indicating that additional factors cooperate with TET2 loss to promote disease. TET2 loss is also associated with innate immune functional deficits (Huerga Encabo et al., Cell Stem Cell, 2023). Human patient data and TET2-deficient mouse models show impaired survival and heightened pathology during bacterial infection (Quin et al., J Clin Invest, 2024). Additionally, inflammation elicited by LPS drives clonal expansion and disease progression in TET2-deficient mice (Cai et al., Cell Stem Cell, 2018). How innate immune inflammation elicited by physiological challenges (infection) interacts with TET2 loss throughout an individual's lifetime is not well understood, hindering development of therapeutic intervention. Receptor-interacting serine/threonine kinase 1 (RIPK1) presents one target to mediate the proinflammatory effects of TET2 loss. RIPK1 activates proinflammatory signaling via toll-like receptors (TLRs) and TNFαR1 through adaptor protein interaction, and it also upregulates necroptotic signaling in human MDS patient bone marrow (Newton, Cold Spring Harb Perspect Biol, 2020; Zou et al., Blood, 2021), placing RIPK1 at the nexus of multiple inflammatory pathways implicated in MDS.

Infectious or inflammatory challenges induce metabolic and epigenetic changes in hematopoietic stem and progenitor cells (HSPC) that confer capacity for an enhanced innate immune response to subsequent infection in innate immune memory. Innate immune memory can be elicited by administering monophosphoryl lipid A (MPLA) a less toxic LPS derivative and TLR4 agonist (Fensterheim et al., J Immunol, 2018). Given the role of TET2 in epigenetic regulation and effect of TET2 loss on innate immune function, we asked whether vavTet2^fl/fl mice can respond to MPLA to improve infection clearance, as well as whether inflammation induced by MPLA and infection promotes disease-related hematopoietic dysfunction. We also tested whether RIPK1 inhibition vavTet2^fl/flRipk1^D138N/+ (Roderick et al., PNAS, 2014) can improve the inflammatory consequences of infection-induced inflammation.

We employed a Pseudomonas aeruginosa sepsis model, and weinjected WT, vavTet2^fl/fl, and vavTet2^fl/flRipk1^D138N/+ mice with MPLA, and 3 days later, infected with P. aeruginosa. We find that vavTet2^fl/fl and vavTet2^fl/flRipk1^D138N/+ mice have impaired infection responses compared to WT controls in non-pretreated groups. Additionally, MPLA pretreatment incompletely protects against infection in vavTet2^fl/fl mice. Though all groups recruit innate immune cells to infection sites, we note ROS production and phagocytosis reductions in vavTet2^fl/fl mice, which may contribute to impairments in pathogen clearance. We also examined the impact of MPLA with P. aeruginosa on bone marrow mature innate immune cells via spectral flow cytometry. We found that TET2-deficient mice increase myeloid-biased differentiation, though neutrophils and macrophages display impaired differentiation relative to WT. Moreover, we observed significant effects of MPLA with infection on the stem and progenitor compartment in TET2 loss. VavTet2^fl/fl mice markedly expand myeloid-biased progenitors at the expense of the erythroid- and megakaryocyte-biased progenitors, resembling MDS-like disease progression. Intriguingly, inhibiting inflammation by RIPK1 inactivation dampens deleterious effects on hematopoiesis. Collectively, these results provide insight into how, in a physiologically relevant infection model, TET2deficiency impairs immune responses and drives inflammation. We further show that prior innate immune activation with MPLA improves infection response but impairs hematopoiesis in a RIPK1-dependent manner.