The In Vivo Granulopoietic Response to Dexamethasone Injection Is Abolished in Perforin‐Deficient Mutant Mice and Corrected by Lymphocyte Transfer from Nonsensitized Wild‐Type Donors

Abstract

Exogenously administered glucocorticoids enhance eosinophil and neutrophil granulocyte production from murine bone-marrow. A hematological response dependent on endogenous glucocorticoids underlies bone-marrow eosinophilia induced by trauma or allergic sensitization/challenge. We detected a defect in granulopoiesis in nonsensitized, perforin-deficient mice. In steady-state conditions, perforin- (Pfp-) deficient mice showed significantly decreased bone-marrow and blood eosinophil and neutrophil counts, and colony formation in response to GM-CSF, relative to wild-type controls of comparable age and/or weight. By contrast, peripheral blood or spleen total cell and lymphocyte numbers were not affected by perforin deficiency. Dexamethasone enhanced colony formation by GM-CSF-stimulated progenitors from wild-type controls, but not Pfp mice. Dexamethasone injection increased bone-marrow eosinophil and neutrophil counts in wild-type controls, but not Pfp mice. Because perforin is expressed in effector lymphocytes, we examined whether this defect would be corrected by transferring wild-type lymphocytes into perforin-deficient recipients. Short-term reconstitution of the response to dexamethasone was separately achieved for eosinophils and neutrophils by transfer of distinct populations of splenic lymphocytes from nonsensitized wild-type donors. Transfer of the same amount of splenic lymphocytes from perforin-deficient donors was ineffective. This demonstrates that the perforin-dependent, granulopoietic response to dexamethasone can be restored by transfer of innate lymphocyte subpopulations.

Surgical and immune reconstitution murine models in bone marrow research: Potential for exploring mechanisms in sepsis, trauma and allergy

“…A systematic screening showed that while wild-type C57BL/6 controls (B6) respond to glucocorticoid administration with bone marrow eosinophilia (thereby mimicking the effect of surgical trauma alone in the EWI model), perforin-deficient knockout mice from the same background lack this response. Reconstitution of the glucocorticoid-induced eosinophilic response is achieved through transfer of splenic T lymphocytes from wild-type (but not from perforin-deficient) donors to perforin-deficient recipients[ 184 ]. Other strains, not restricted to the B6 background, were also shown to lack an eosinophilic response to exogenous and/or endogenous glucocorticoid exposure in the bone marrow (manuscript in preparation).…”

Odd couple: The unexpected partnership of glucocorticoid hormones and cysteinyl-leukotrienes in the extrinsic regulation of murine bone-marrow eosinopoiesis

“…Hence, evidence of a link between GC and bone-marrow eosinophilia was consistently provided by experiments ranging from pharmacological through physiological to immunological settings, which are also summarized in Table 1 . This coherence of effects is to be expected from the well-established fact that GCs, synthetic or natural, act through the same receptor, which is blocked by RU486 (mifepristone[ 45 , 51 - 53 ]).…”

“…Dexamethasone did not induce bone-marrow eosinophilia in vivo in our original study, which used mice of the BALB/c background; however, it did prime bone-marrow for strongly enhanced responses to IL-5 ex vivo over a period of from 24 h[ 51 ] up to 4 wk after injection (manuscript in preparation); more recently, however, an important difference between strains of distinct backgrounds was observed for this drug effect, since bone-marrow eosinophilia was observed in C57BL/6 mice injected with dexamethasone, 24 h after injection, unlike BALB/c controls[ 53 ]. In both BALB/c and C57BL/6 mice, dexamethasone primed bone-marrow for increased eosinophil production in IL-5-stimulated cultures; dexamethasone did not replace IL-5 as a primary eosinopoietic stimulus, but greatly enhanced its effectiveness.…”

“…However, bone-marrow of naive mice[ 70 ], or from sensitized mice pretreated with RU486 before challenge (manuscript in preparation), does respond to CysLT in culture in the absence of exogenously added GC. Also, bone-marrow from unsensitized C57BL/6 mice shows eosinophilia in vivo after dexamethasone administration[ 53 ], in the absence of any known CysLT inducer, just as dexamethasone enhances eosinopoiesis in culture without addition of CysLT. The effectiveness of both partners in the absence of the other is thus established, showing that they have independent pharmacological effects outside the framework of sensitization/challenge.…”

“… A graphical abstract of the main events identified in extrinsic regulation of bone-marrow eosinopoiesis, and of the hypothetical interactions of tumor necrosis factor-α with the underlying mechanisms. Colored boxes and arrows identify different classes of agents and their actions as follows: Orange, extrinsic suppressors of murine bone-marrow eosinopoiesis both in vitro [ 23 , 26 , 72 , 73 ] and in vivo [ 47 , 54 ]; light blue, extrinsic enhancers of eosinopoiesis in vitro [ 25 , 36 , 51 , 70 ] and in vivo [ 45 , 47 , 52 , 53 ]; yellow, essential components of a proapototic sequence (iNOS-CD95L-dependent pathway[ 54 , 72 , 73 ]) which is susceptible to activation by the first (orange-labeled) and blockade by the second (light blue-labeled) sets of extrinsic regulators; lavender, TNF-α, presenting both constitutive (continuous arrow) and challenge-induced (discontinous arrow) effects, inside the bone-marrow, besides its extramedullary actions[ 45 ] as activator of the HPA axis (not shown). TNF-α: Tumor necrosis factor-α.…”