https://orcid.org/0000-0001-8760-8630
Key Points
GSDMD contributes to focal crystalline thrombotic angiopathy and its consequences: ischemic tissue infarction and organ failure.
GSDMD drives neutrophil necrosis, maturation, and tissue recruitment during focal crystalline thrombotic angiopathy.
Thrombotic microangiopathy (TMA) is characterized by immunothrombosis and life-threatening organ failure but the precise underlying mechanism driving its pathogenesis remains elusive. In this study, we hypothesized that gasdermin D (GSDMD), a pore-forming protein that serves as the final downstream effector of the pyroptosis/interleukin-1β (IL-1β) pathway, contributes to TMA and its consequences by amplifying neutrophil maturation and subsequent necrosis. Using a murine model of focal crystalline TMA, we found that Gsdmd deficiency ameliorated immunothrombosis, acute tissue injury, and failure. Gsdmd−/− mice exhibited a decrease in mature IL-1β, as well as in neutrophil maturation, β2-integrin activation, and recruitment to TMA lesions, in which they formed reduced neutrophil extracellular traps in both arteries and interstitial tissue. The GSDMD inhibitor disulfiram dose-dependently suppressed human neutrophil pyroptosis in response to cholesterol crystals. Experiments with GSDMD–deficient, human–induced, pluripotent stem cell–derived neutrophils confirmed the involvement of GSDMD in neutrophil β2-integrin activation, maturation, and pyroptosis. Both prophylactic and therapeutic administration of disulfiram protected the mice from focal TMA, acute tissue injury, and failure. Our data identified GSDMD as a key mediator of focal crystalline TMA and its consequences, including ischemic tissue infarction and organ failure. GSDMD could potentially serve as a therapeutic target for the systemic forms of TMA.
Comments
GSDMD acts as an amplifier in acute neutrophil inflammation
In most studies, GSDMD was regarded as a pore-forming protein serving as the executor of pyroptosis.2 The cleaved N-terminal GSDMD and cleaved caspase-1/11 are crucial markers of pyroptosis, characterizing the activation of inflammasome-associated cascades. Neutrophils are the first innate immune cells recruited from bone marrow and blood to tissues such kidney.3 Nevertheless, it’s a double-edged sword for neutrophil mobilization in infection and autoimmune diseases. Uncontrolled amplification of neutrophil inflammation can result in the activation of complement, coagulation cascade and adaptive immune system.
Watanabe-Kusunoki et al found both GSDMD deficiency and pharmacological inhibition of GSDMD by DSF attenuated renal injury in cholesterol crystals induced focal TMA. Intriguingly, the authors demonstrated the role of GSDMD in neutrophil maturation and mobilization beyond necrosis.1 As previously mentioned, mature neutrophils are released from the bone marrow into the circulation, during which, increased expression of adhesion molecules and their receptors allows for this process. The authors showed an impaired β2 integrin activation in Gsdmd-/- mice and diminished expression of CXCR2 in Gsdmd-/- bone marrow neutrophils. Overall, the authors proposed a new function of GSDMD in neutrophils under inflammatory condition although more precise mechanism needed further investigation.
In fact, GSDMD serves as an amplifier in acute neutrophil inflammation. Under the stimulation of inflammatory factor such as LPS, the expression level of GSDMD in neutrophils is increased. On the one hand, oligomerized GSDMD-N terminal would insert in the membrane of azurophilic granules, mitochondria, and cytomembrane and open a pore, permitting calcium influx, the activation of neutrophil serine protease and the release of IL-1β, mitochondria DNA.4-6 For relatively moderate stimulation, neutrophils will extrude its DNA and cytoplasmic contents in the process of NETosis. While stimulated by acute and severe factors, netrophils will die in a manner dependent on NINJ-1 mediated membrane rupture.7 Both the two pathways can contribute to the amplification of inflammation. On the other hand, increased expression of GSDMD contributes to the mobilization and maturation process of neutrophils, facilitating the migration of neutrophils from bone marrow to blood, then mobilize into tissues.1,8 Thus GSDMD is involved in the infiltration and activation of neutrophil in tissues, amplifying inflammation by changing cellular kinetics and modulating cell death.
In summary, Watanabe-Kusunoki et al’s work broadens our horizon about the role of GSDMD in neutrophil inflammation and provides a potential therapeutic target for focal TMA. But more precise mechanism about GSDMD in neutrophil mobilization and maturation needs further exploration. Moreover, GSDMD conditional knockout in neutrophils model is needed to exclude the impact of other cell types. And the role of GSDMD in more neutrophil-related diseases beyond TMA is encouraged to investigate.
Competing interests
No competing interests.
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