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Injury of the skin from exposure to toxic chemicals leads to the release of inflammatory mediators and the recruitment of immune cells. Nitrogen mustard (NM) and other alkylating agents cause severe cutaneous damage for which there are limited treatment options. Here, we show that combined treatment of vitamin D3 (VD3) and spironolactone (SP), a mineralocorticoid receptor antagonist, significantly improves the resolution of inflammation and accelerates wound healing after NM exposure. SP enhanced the inhibitory effect of VD3 on nuclear factor‐kB activity. Combined treatment of NM‐exposed mice with VD3 and SP synergistically inhibited the expression of iNOS in the skin and decreased the expression of matrix metallopeptidase‐9, C‐C motif chemokine ligand 2, interleukin (IL)‐1α, and IL‐1β. The combined treatment decreased the number of local proinflammatory M1 macrophages resulting in an increase in the M2/M1 ratio in the wound microenvironment. Apoptosis was also decreased in the skin after combined treatment. Together, this creates a proresolution state, resulting in more rapid wound closure. Combined VD3 and SP treatment is effective in modulating the immune response and activating anti‐inflammatory pathways in macrophages to facilitate tissue repair. Altogether, these data demonstrate that VD3 and SP may constitute an effective treatment regimen to improve wound healing after NM or other skin chemical injury., Our results demonstrate that vitamin D3 in combination with spironolactone treatment improves wound healing after nitrogen mustard (NM) exposure by modulating the immune response and activating anti‐inflammatory pathways. In addition to supportive treatment, this may expand the currently limited treatment options to improve clinical outcomes for NM injury.

High-throughput quantification of the post-translational modification of many individual protein samples is challenging with current label-based methods. This paper demonstrates an efficient method that addresses this gap by combining Escherichia coli-based cell-free protein synthesis (CFPS) and self-assembled monolayers for matrix-assisted laser desorption/ionization mass spectrometry (SAMDI-MS) to analyze intact proteins. This high-throughput approach begins with polyhistidine-tagged protein substrates expressed from linear DNA templates by CFPS. Here, we synthesized an 87-member library of the E. coli Immunity Protein 7 (Im7) containing an acceptor sequence optimized for glycosylation by the Actinobacillus pleuropneumoniae N-glycosyltransferase (NGT) at every possible position along the protein backbone. These protein substrates were individually treated with NGT and then selectively immobilized to self-assembled monolayers presenting nickel-nitrilotriacetic acid (Ni-NTA) complexes before final analysis by SAMDI-MS to quantify the conversion of substrate to glycoprotein. This method offers new opportunities for rapid synthesis and quantitative evaluation of intact glycoproteins.

Haematopoietic stem cells (HSCs) maintain lifelong blood production and increase blood cell numbers in response to chronic and acute injury. However, the mechanism(s) by which inflammatory insults are communicated to HSCs and their consequences for HSC activity remain largely unknown. Here, we demonstrate that interleukin-1 (IL-1), which functions as a key pro-inflammatory 'emergency' signal, directly accelerates cell division and myeloid differentiation of HSCs through precocious activation of a PU.1-dependent gene program. Although this effect is essential for rapid myeloid recovery following acute injury to the bone marrow, chronic IL-1 exposure restricts HSC lineage output, severely erodes HSC self-renewal capacity, and primes IL-1-exposed HSCs to fail massive replicative challenges such as transplantation. Importantly, these damaging effects are transient and fully reversible on IL-1 withdrawal. Our results identify a critical regulatory circuit that tailors HSC responses to acute needs, and is likely to underlie deregulated blood homeostasis in chronic inflammation conditions.

Quiescence acts as a safeguard mechanism to ensure survival of the HSC pool during chronic IFN-1 exposure, Type I interferons (IFN-1s) are antiviral cytokines that suppress blood production while paradoxically inducing hematopoietic stem cell (HSC) proliferation. Here, we clarify the relationship between the proliferative and suppressive effects of IFN-1s on HSC function during acute and chronic IFN-1 exposure. We show that IFN-1–driven HSC proliferation is a transient event resulting from a brief relaxation of quiescence-enforcing mechanisms in response to acute IFN-1 exposure, which occurs exclusively in vivo. We find that this proliferative burst fails to exhaust the HSC pool, which rapidly returns to quiescence in response to chronic IFN-1 exposure. Moreover, we demonstrate that IFN-1–exposed HSCs with reestablished quiescence are largely protected from the killing effects of IFNs unless forced back into the cell cycle due to culture, transplantation, or myeloablative treatment, at which point they activate a p53-dependent proapoptotic gene program. Collectively, our results demonstrate that quiescence acts as a safeguard mechanism to ensure survival of the HSC pool during chronic IFN-1 exposure. We show that IFN-1s can poise HSCs for apoptosis but induce direct cell killing only upon active proliferation, thereby establishing a mechanism for the suppressive effects of IFN-1s on HSC function.

Hematopoietic stem cells (HSCs) maintain lifelong blood homeostasis. While many of the cell-intrinsic mechanisms regulating HSC function at steady state have been well characterized, the role of inflammatory cytokines and other environmental factors in tailoring blood production following physiological insults has become a topic of emerging interest. The cytokine interleukin-1 (IL-1) is a prototypical pro-inflammatory cytokine that plays a key role in host inflammatory responses to injury and infection, and is associated with elevated myeloid cell production. Importantly, IL-1 also drives a wide range of chronic inflammatory conditions such as diabetes, obesity, and arthritis that are often characterized by deregulated blood homeostasis. Here, we show at single-cell resolution using continuous tracking technology that IL-1 drives accelerated HSC cell division kinetics and myeloid differentiation via the rapid activation of a precocious PU.1-dependent myeloid gene program. Activation of this program requires direct IL-1R signaling and subsequent activation of IKK kinases, and instructively primes HSCs to adopt a myeloid fate. Strikingly, we demonstrate that IL-1 produced by myeloid cells and endothelial cells of the bone marrow (BM) niche exerts similar effects in vivo, and is required for efficient myeloid recovery following acute challenges such as transplantation or myeloablation. On the other hand, we find that chronic IL-1 exposure substantially remodels HSC blood output, resulting in myeloid overproduction and expansion of myeloid-biased multipotent progenitor (MPP) compartments at the expense of lymphoid and erythroid lineages. Critically, chronic IL-1 erodes HSC self-renewal, significantly impairing their regenerative capacity following transplantation. On the other hand, chronically exposed HSCs recover their function upon IL-1 withdrawal. Collectively, these findings identify IL-1 as a critical regulator of HSC fate and lineage specification via activation of a PU.1 circuit. They also demonstrate a role for IL-1 as a double-edged sword in HSC biology, promoting HSC regeneration in response to acute insults while severely disrupting HSC self-renewal and lineage output during chronic exposure, hence identifying IL-1 as an important and therapeutically targetable factor underwriting myeloid overproduction and other deregulations that contribute to the pathogenesis of a variety of chronic inflammatory diseases and blood disorders. Disclosures No relevant conflicts of interest to declare.

Hematopoietic stem cells (HSCs) are a rare population of self-renewing bone marrow (BM) cells that give rise to all lineages of mature blood cells including those comprising the immune system. While many regulatory factors controlling HSC differentiation and blood production have been identified, the role of inflammatory cytokines in this process is still largely unknown. Interleukin-1 (IL-1) is a prototypical inflammatory cytokine with critical functions in innate immune responses. While IL-1 is associated with increased myeloid cell production, whether it regulates myeloid lineage specification from HSCs remains unclear. Here, we use cutting-edge approaches to directly interrogate the role of IL-1 in regulating HSC differentiation during steady state and in response to hematopoietic stress. Using continuous single-cell tracking technology, we find that IL-1 accelerates HSC growth and instructs HSC differentiation along the granulocyte–macrophage (GM) lineage in vitro. Strikingly, these effects are accompanied by the rapid activation of a gene program driven by the transcription factor Pu.1, the master regulator of GM lineage commitment, as shown by qRT-PCR analyses and lineage tracking in Pu.1-eYFP reporter mice. Consistent with these in vitro observations, the pool of HSC-derived progenitor cells giving rise to the GM lineage is significantly reduced in size in IL-1 receptor (Il1r1)-deficient mice and Il1r1-deficient mice show significantly impaired recovery of GM-lineage output following 5-FU-mediated myeloablation. We are now working at identifying the cellular components of the BM microenvironment that produce IL-1 in these conditions. Collectively, our results identify IL-1 as a key regulator of myeloid cell production from HSCs and provide compelling evidence for a direct role of inflammatory cytokines in shaping the immune system. They advance our understanding of how blood cell production is regulated in both steady state and stress conditions, which could have important implications for the treatment of acute inflammation and autoimmune diseases.