Kinetics and mechanisms of recombinant human interleukin 1 and tumor necrosis factor-alpha-induced changes in circulating numbers of neutrophils and lymphocytes

Human recombinant interleukins 1 alpha and 1 beta (rIL-1 alpha and -1 beta) both induced monophasic peripheral neutrophilia and lymphopenia in Lewis rats 1.5 hr after i.v. injection. The kinetics of rIL-1 alpha- and -1 beta-induced neutrophilia were similar to those induced by human monocyte-derived IL-1, IL-1 alpha, and IL-1 beta, and the peripheral neutrophilia was accompanied by a marked decrease in marrow neutrophils. Arachidonic acid metabolites are implicated as biochemical intermediates in the production of the neutrophilia but not lymphopenia, since indomethacin and dexamethasone both completely abrogated IL-1-induced neutrophilia but did not affect the IL-1-induced lymphopenia. Acetylsalicylic acid, a cyclooxygenase inhibitor, did not inhibit IL-1-induced neutrophilia, suggesting that products of the lipoxygenase rather than the cyclooxygenase pathway of arachidonate metabolism may contribute to the neutrophilia. Human recombinant tumor necrosis factor-alpha (rTNF) administered i.v. to Lewis rats induced peripheral neutropenia, two peaks of neutrophilia, and lymphopenia. A wide range of doses of rTNF resulted in an initial neutropenia at 0.5 hr after injection followed by a first peak of neutrophilia at 1.5 hr and a second peak of neutrophilia at 6 hr. The initial neutropenia and the first peak of neutrophilia were not inhibited by pretreatment of rats with dexamethasone, indomethacin, or aspirin. The second peak of neutrophilia was inhibited by both dexamethasone and indomethacin, but was not at all inhibited by aspirin, suggesting that the second peak of neutrophilia is mediated by the release of endogenous cytokines, especially by IL-1, since exogenous IL-1-induced neutrophilia is also completely inhibited by dexamethasone and indomethacin but not by aspirin. The TNF-induced peripheral neutrophilia is also accompanied by a significant depletion of bone marrow neutrophils, indicating that the source of increased circulating neutrophils is, at least in part, via recruitment of marrow neutrophils. Systemic blood pressure was not affected by IL-1 or rTNF at the dosages employed, showing that the changes in circulating leukocyte subsets were not attributable to hemodynamic changes nor to the hemodynamic change-related release of adrenal hormones. Adrenalectomy did not alter the IL-1- or rTNF-induced neutrophilia or lymphopenia, also demonstrating that neither monokine mediates its hematologic effects on peripheral blood leukocytes via the release of adrenal hormones.(ABSTRACT TRUNCATED AT 400 WORDS)     

Role of Beta-adrenergic Receptors and Sirtuin Signaling in the Heart During Aging,Heart Failure,and Adaptation to Stress

In the heart, catecholamine effects occur by activation of beta-adrenergic receptors (β-ARs), mainly the beta 1 (β₁-AR) and beta 2 (β₂-AR) subtypes, both of which couple to the Gs protein that activates the adenylyl cyclase signaling pathway. The β₂-ARs can also couple to the Gi protein that counterbalances the effect of the Gs protein on cyclic adenosine monophosphate production and activates the phosphatidylinositol 3-kinase (PI3K)–Akt signaling pathway. In several cardiovascular disorders, including heart failure, as well as in aging and in animal models of environmental stress, a reduction in the β₁/β₂-AR ratio and activation of the β₂-AR-Gi-PI3K–Akt signaling pathway have been observed. Recent studies have shown that sirtuins modulate certain organic processes, including the cellular stress response, through activation of the PI3K–Akt signaling pathway and of downstream molecules such as p53, Akt, HIF1-α, and nuclear factor-kappa B. In the heart, SIRT1, SIRT3, and β₂-ARs are crucial to the regulation of the cardiomyocyte energy metabolism, oxidative stress, reactive oxygen species production, and autophagy. SIRT1 and the β₂-AR-Gi complex also control signaling pathways of cell survival and death. Here, we review the role played by β₂-ARs and sirtuins during aging, heart failure, and adaptation to stress, focusing on the putative interplay between the two. That relationship, if proven, merits further investigation in the context of cardiac function and dysfunction.     

β2- and β3-, but not β1-adrenergic receptors are involved in osteogenesis of mouse mesenchymal stem cells via cAMP/PKA signaling

The osteogenic capacity of mesenchymal stem cells (MSCs) and the importance of β-adrenergic signals in bone formation and resorption have been well investigated. However, little is known about the development of β-adrenergic receptor (β-AR) systems and the role of β-adrenergic signals in osteogenic differentiation of MSCs, which is critically important in bone physiology and pharmacology. In this study, we demonstrated that both the mRNA and protein levels of β2- and β3-AR are up-regulated following osteogenesis of mouse MSCs. We also established that β-AR agonists negatively while antagonists positively affect MSC osteogenesis. Both β2- and β3-AR are involved in MSC osteogenesis, with β2-AR being dominant. The effect of β-ARs on MSC osteogenesis is partly mediated via the cAMP/PKA signaling. These findings suggest that MSC is also a target for β-adrenergic regulation and β-adrenergic signaling plays a role in MSC osteogenesis.     

β-Adrenergic inhibition of contractility in L6 skeletal muscle cells

The β-adrenoceptors (β-ARs) control many cellular processes. Here, we show that β-ARs inhibit calcium depletion-induced cell contractility and subsequent cell detachment of L6 skeletal muscle cells. The mechanism underlying the cell detachment inhibition was studied by using a quantitative cell detachment assay. We demonstrate that cell detachment induced by depletion of extracellular calcium is due to myosin- and ROCK-dependent contractility. The β-AR inhibition of L6 skeletal muscle cell detachment was shown to be mediated by the β(2)-AR and increased cAMP but was surprisingly not dependent on the classical downstream effectors PKA or Epac, nor was it dependent on PKG, PI3K or PKC. However, inhibition of potassium channels blocks the β(2)-AR mediated effects. Furthermore, activation of potassium channels fully mimicked the results of β(2)-AR activation. In conclusion, we present a novel finding that β(2)-AR signaling inhibits contractility and thus cell detachment in L6 skeletal muscle cells by a cAMP and potassium channel dependent mechanism.     

Cardiac pressure overload hypertrophy is differentially regulated by β-adrenergic receptor subtypes

In isolated myocytes, hypertrophy induced by norepinephrine is mediated via α(1)-adrenergic receptors (ARs) and not β-ARs. However, mice with deletions of both major cardiac α(1)-ARs still develop hypertrophy in response to pressure overload. Our purpose was to better define the role of β-AR subtypes in regulating cardiac hypertrophy in vivo, important given the widespread clinical use of β-AR antagonists and the likelihood that patients treated with these agents could develop conditions of further afterload stress. Mice with deletions of β(1), β(2), or both β(1)- and β(2)-ARs were subjected to transverse aortic constriction (TAC). After 3 wk, β(1)(-/-) showed a 21% increase in heart to body weight vs. sham controls, similar to wild type, whereas β(2)(-/-) developed exaggerated (49% increase) hypertrophy. Only when both β-ARs were ablated (β(1)β(2)(-/-)) was hypertrophy totally abolished. Cardiac function was preserved in all genotypes. Several known inhibitors of cardiac hypertrophy (FK506 binding protein 5, thioredoxin interacting protein, and S100A9) were upregulated in β(1)β(2)(-/-) compared with the other genotypes, whereas transforming growth factor-β(2), a positive mediator of hypertrophy was upregulated in all genotypes except the β(1)β(2)(-/-). In contrast to recent reports suggesting that angiogenesis plays a critical role in regulating cardiac hypertrophy-induced heart failure, we found no evidence that angiogenesis or its regulators (VEGF, Hif1α, and p53) play a role in compensated cardiac hypertrophy. Pressure overload hypertrophy in vivo is dependent on a coordination of signaling through both β(1)- and β(2)-ARs, mediated through several key cardiac remodeling pathways. Angiogenesis is not a prerequisite for compensated cardiac hypertrophy.     

β2-Adrenoceptor transfection enhances contractile reserve of isolated rat ventricular myocytes exposed to chronic isoprenaline stimulation by improving β1-adrenoceptor responsiveness

Context: Heart failure (HF) is a progressive deterioration in heart function associated with overactivity of the sympathetic nervous system. Elevated sympathetic nervous system activity down regulates the β-adrenergic signal system, suppressing β-adrenoceptors (β-ARs)-mediated contractile support in the failing heart.

Objective: We investigated the effects of β₂-AR gene transfer on shortening amplitude of isolated ventricular myocytes under chronic exposure to isoprenaline (ISO), and further determine the contributions of β₁-AR and β₂-AR to the contraction.

Materials and methods: Cardiomyocytes were isolated from adult rat hearts and then transfected with β₂-AR gene using an adenovirus vector. Four hours after the infection, cardiomyocytes were treated with ISO for another 24 hours to imitate high levels of circulating catecholamines in HF. Western blotting was performed to measure myocardial protein expression of β₂-AR. Video-based edge-detection system was used to evaluate basal and ISO-stimulated shortening amplitudes of cardiomyocytes.

Results: β₂-AR gene transfer increased β₂-AR protein content. Chronic ISO stimulation produced a negative inotropic response, whereas acute ISO stimulation showed a positive inotropic response. β₂-AR gene transfer had no significant effects on shortening amplitude of cardiomyocytes under normal conditions, but enhanced the blunted contraction of cardiomyocytes under pathological conditions induced by chronic ISO stimulation, and the effect was inhibited by β₁-AR antagonist, CGP 20712A, instead of β₂-AR antagonist, ICI 118,551.

Discussion and conclusions: We conclude that β₂-AR gene transfer in isolated ventricular myocytes under chronic ISO stimulation improves cellular contraction, and the beneficial effects might be mediated by improving β₁-adrenoceptor responsiveness.     

Adrenergic Receptors and Fat Cells: Differential Recruitment by Physiological Amines and Homologous Regulation

The control of fat cell lipolysis by the catecholamines involves at least four different adrenoceptor subtypes; three β (β1-, β2-, and β3-ARs) and one α2-adrenoceptor(α2-AR). The physiological importance of the β- and α2A-ARs varies according to the species, the sex, the age, the anatomical location of fat deposits and the degree of obesity in humans and animals. The physiological amines operate through differential recruitment of these sites on the basis of their relative affinities. This point has been assessed by in vitro studies and has partly been confirmed in in vivo experiments using selected a/β-AR antagonists and in situ microdialysis. The affinity of the β3-AR for catecholamines is less than that of the classical β1- and β2-ARs in the various species investigated. Conversely, it is the α2-AR which exhibit the highest affinity for the physiological amines in all fat cells. The relative order of affinity of the various fat cell ARs for the physiological amines defined in binding studies and in vitro ass ays is α2 > β1 > β2 > β3 for norepinephrine and α2 >β2 > β1> β3 for epinephrine. When considering differential β-AR recruitment by catecholamines, it is the β1-AR which is always activated at the lowest norepinephrine levels, whatever the species, while the activation of the β3-AR requires higher norepinephrine levels. In addition to the differential recruitment, differential regulation by hormones could also occur for each fat cell AR subtype. The α2-and β3-ARs are less prone to desensitization and down-regulation by comparison with the β1- and β2-AR.     

Rab1 GTPase promotes expression of β-adrenergic receptors in rat pulmonary microvascular endothelial cells

It is known that Rab1 regulates the expression and function of beta-adrenoceptors (β-ARs) in many cells. However, the effect of these changes in rat pulmonary microvascular endothelial cells (RPMVECs) is not known. In the present study, we investigated the role of Rab1, a Ras-like GTPase that coordinates protein transport from the endoplasmic reticulum (ER) to the Golgi body and regulates the cell-surface targeting and function of endogenous β-ARs in RPMVECs in the presence of lipopolysaccharide (LPS).We found that lentivirus-driven expression of wild-type Rab1 (Rab1WT) in RPMVECs strongly enhanced the amount of β-ARs on the cell surface, whereas the dominant-negative mutant Rab1N124I significantly attenuated β-ARs expression on the cell surface. In addition, LPS stimulation significantly reduced β-ARs expression on the cell surface in RPMVECs; however, this effect was reversed by over-expression of wild-type Rab1WT. Fluorescent microscopy analysis demonstrated that expression of Rab1N124I and Rab1 small interfering RNA (siRNA) significantly induced the accumulation of green fluorescent protein (GFP)-tagged β₂-AR in the ER. Consistent with their effects on β-ARs export, Rab1WT and Rab1N124I differentially modified the β-AR-mediated activation of extracellular signal-regulated kinase1/2 (ERK1/2). Importantly, over-expression of Rab1WT markedly reduced LPS-induced hyper-permeability of RPMVECs by increasing the expression of β₂-AR on the cell surface. These data reveal that β-ARs function in RPMVECs could be modulated by manipulating β-ARs traffic from the ER to the Golgi body. We propose the ER-to-Golgi transport as a regulatory site for control of permeability of RPMVECs.     

Are beta-adrenergic receptors in the hippocampal CA1 region required for retrieval of contextual fear memory?

It is well established that β-adrenoceptors (β-ARs) in the hippocampal CA1 region are involved in regulating synaptic plasticity and are essential for acquisition and consolidation of spatial memory and contextual fear memory. Previous studies reported that β-ARs in the CA1 region are also involved in memory retrieval. The present study re-examined the role of hippocampal β-ARs in retrieval of conditioned contextual fear. We bilaterally infused a high dose of the β-AR antagonist propranolol (15 μg in 1 μl saline) into the CA1 region 30 min before retention test and found that propranolol produced no deficit in retrieval of either 1-day or 7-day contextual fear. We then examined if β-AR stimulation would produce a beneficial effect. The β-AR agonist isoproterenol (10 μg in 1 μl saline) was infused into the CA1 region 30 min before retention test. Surprisingly, isoproterenol did not enhance but severely disrupted retrieval of 7-day contextual fear memory, with no impact on retrieval of 1-day contextual fear memory. The present study argues against the previous conclusion that β-ARs in the CA1 region play a role in memory retrieval. β-ARs in the CA1 region may be dispensable for retrieval of conditioned contextual fear.     

A kinetic model of bone marrow neutrophil production that characterizes late phenotypic maturation

Acute inflammatory stimuli rapidly mobilize neutrophils from the bone marrow by shortening postmitotic maturation time and releasing younger neutrophils; however, the kinetics of this change in maturation time remains unknown. We propose a kinetic model that examines the rate of change in neutrophil average age at exit from the bone marrow during active mobilization to quantify this response and use this model to examine the temporal profile of late neutrophil phenotypic maturation. Total and CD10(-)/CD16(low) circulating neutrophils were quantified in cardiac surgery patients during extracorporeal circulation (ECC). Net growth in the circulating neutrophil pool occurred during the procedural (0.04 +/- 0.02 x 10(9) x l(-1) x min(-1)), warming (0.14 +/- 0.02 x 10(9) x l(-1) x min(-1)), and weaning (0.12 +/- 0.06 x 10(9) x l(-1) x min(-1)) phases of ECC. When applied to our differential equation mathematical model, these results predict that neutrophil average age at exit from the bone marrow decreased continually during ECC, resulting in average neutrophil release 8.44 +/- 2.20 h earlier during the weaning phase than at the beginning of ECC sampling. Modeling of concurrent changes in CD10(-)/CD16(low) neutrophil numbers indicates that CD10 expression is directly related to neutrophil mean age and predicts that the proportion of mobilizable postmitotic neutrophils that are CD10(+) increases from 64 to 81% during these sampled 8.4 h of maturation.     

Blockade of S100A8 and S100A9 suppresses neutrophil migration in response to lipopolysaccharide

Recently, proinflammatory activities had been described for S100A8 and S100A9, two proteins found at inflammatory sites and within the neutrophil cytoplasm. In this study, we investigated the role of these proteins in neutrophil migration in vivo in response to LPS. LPS was injected into the murine air pouch, which led to the release of S100A8, S100A9, and S100A8/A9 in the pouch exudates that preceded accumulation of neutrophils. Passive immunization against S100A8 and S100A9 led to a 52% inhibition of neutrophil migration in response to LPS at 3 h postinjection. Injection of LPS was also associated with an increase in peripheral blood neutrophils and the presence in serum of S100A9 and S100A8/A9. Intravenous injection of S100A8, S100A9, or S100A8/A9 augmented the number of circulating neutrophils and diminished the number of neutrophils in the bone marrow, demonstrating that S100A8 and S100A9 induced the mobilization of neutrophils from the bone marrow to the blood. Finally, passive immunization with anti-S100A9 inhibited the neutrophilia associated with LPS injection in the air pouch. These results suggest that S100A8 and S100A9 play a role in the inflammatory response to LPS by inducing the release of neutrophils from the bone marrow and directing their migration to the inflammatory site.     

The role of β-adrenergic receptor signaling in the proliferation of hemangioma-derived endothelial cells

Background

Infantile hemangioma (IH) is a benign vascular neoplasm that arises from the abnormal proliferation of endothelial cells and enhanced angiogenesis. Recently, propranolol has been found to be effective in the management of IH, suggesting that β-adrenergic receptors (β-ARs) may play an important role in the pathogenesis of IH.

Results

In the present study, we investigated the β-adrenergic signaling that is associated with hemangioma-derived endothelial cell (HemEC) proliferation. The results showed that both β₁- and β₂-ARs were expressed in HemECs. Stimulation of the β-ARs by isoprenaline induced cell proliferation and elevation of second messenger cAMP levels. The proliferation-promoting action of isoprenaline was abolished by a β₁-selective antagonist and was more effectively abolished by a β₂-selective antagonist; the mechanism for the action of the antagonists was a G₀/G₁ phase cell cycle arrest which was associated with decreased cyclin D1, CDK-4, CDK-6 and phospho-Rb expression. Pre-treatment of the cells with VEGFR-2 or ERK inhibitors also prevented the isoprenaline-mediated proliferation of cells. In agreement with the involvement of β-ARs and VEGFR-2 in the HemEC response, β-AR antagonists and the VEGFR-2 inhibitor significantly attenuated isoprenaline-induced ERK phosphorylation. Moreover, treating the cells with isoprenaline markedly increased VEGF-A expression and VEGFR-2 activity in a β₂-AR-dependent manner.

Conclusions

We have demonstrated that the activation of the β-ARs in the ERK pathway may be important mechanisms in promoting HemEC growth. Furthermore, stimulation of the β-AR may transactivate VEGFR-2 signaling and further increase HemEC proliferation.     

Antiangiogenic effects of β2 -adrenergic receptor blockade in a mouse model of oxygen-induced retinopathy

Oxygen-induced retinopathy (OIR) is a model for human retinopathy of prematurity. In mice with OIR, beta-adrenergic receptor (β-AR) blockade with propranolol has been shown to ameliorate different aspects of retinal dysfunction in response to hypoxia. In the present study, we used the OIR model to investigate the role of distinct β-ARs on retinal proangiogenic factors, pathogenic neovascularization and electroretinographic responses. Our results demonstrate that β(2) -AR blockade with ICI 118,551 decreases retinal levels of proangiogenic factors and reduces pathogenic neovascularization, whereas β(1) - and β(3) -AR antagonists do not. Determination of retinal protein kinase A activity is indicative of the fact that β-AR blockers are indeed effective at the receptor level. In addition, the specificity of ICI 118,551 on retinal angiogenesis has been demonstrated by the finding that in mouse retinal explants, β(2) -AR silencing prevents ICI 118,551 effects on hypoxia-induced vascular endothelial growth factor accumulation. In OIR mice, ICI 118,551 is effective in increasing electroretinographic responses suggesting that activation of β(2) -ARs constitutes an important part of the retinal response to hypoxia. Lastly, immunohistochemical studies demonstrate that β(2) -ARs are localized to several retinal cells, particularly to Müller cells suggesting the possibility that β(2) -ARs play a role in regulating vascular endothelial growth factor production by these cells. The present results suggest that pathogenic angiogenesis, a key change in many hypoxic/ischemic vision-threatening retinal diseases, depends at least in part on β(2) -AR activity and indicate that β(2) -AR blockade can be effective against retinal angiogenesis.     

β3-Adrenergic Regulation of L-Type Ca2+ Current and Force of Contraction in Human Ventricle

β₃-Adrenergic receptor (β₃-AR) is expressed in human atrial and ventricular tissues. Recently, we have demonstrated that it was involved in the activation of L-type Ca²⁺ current (I _Ca,L) in human atrial myocytes and the force of contraction of human atrial trabeculae. In the present study, we examined the effect of β₃-AR agonist CGP12177 which also is a β₁-AR/β₂-AR antagonist on I _Ca,L in human ventricular myocytes (HVMs) and the force of contraction of human ventricular trabeculae. CGP12177 stimulated I _Ca,L in HVMs with high potency but much lower efficacy than isoprenaline. The β₃-AR antagonist L-748,337 inhibited the effect of CGP12177. CGP12177 and L748,337 competed selectively on β₃-ARs because L748,337 had no effect on isoprenaline-induced stimulation of I _Ca,L, while CGP12177 completely blocked the effect of isoprenaline. The activation of β₃-ARs by CGP12177 does not involve the activation of G_i proteins because CGP12177 had no effect on forskolin-induced stimulation of I _Ca,L. CGP12177 had no effect on the force of contraction of human ventricular trabeculae. L-NMMA, an inhibitor of NO synthase, and IBMX, a nonselective inhibitor of phosphodiesterases, did not potentiate the effect of CGP12177 either on contraction of human ventricular trabeculae or on I _Ca,L in HVMs. We conclude that in human ventricles β₃-AR activation has no inotropic effect, while it slightly increases I _Ca,L. In contrast to human atrium, the activation of β₃-ARs in human ventricle is not accompanied by increased activity of phosphodiesterases.     

Syntrophin isoforms play specific functional roles in the α1D-adrenergic receptor/DAPC signalosome

α_1D-Adrenergic receptors, key regulators of cardiovascular system function, are organized as a multi-protein complex in the plasma membrane. Using a Type-I PDZ-binding motif in their distal C-terminal domain, α_1D-ARs associate with syntrophins and dystrophin-associated protein complex (DAPC) members utrophin, dystrobrevin and α-catulin. Three of the five syntrophin isoforms (α, β₁ and β₂) interact with α_1D-ARs and our previous studies suggest multiple isoforms are required for proper α_1D-AR function in vivo. This study determined the contribution of each specific syntrophin isoform to α_1D-AR function. Radioligand binding experiments reveal α-syntrophin enhances α_1D-AR binding site density, while phosphoinositol and ERK1/2 signaling assays indicate β₂-syntrophin augments full and partial agonist efficacy for coupling to downstream signaling mechanisms. The results of this study provide clear evidence that the cytosolic components within the α_1D-AR/DAPC signalosome significantly alter the pharmacological properties of α₁-AR ligands in vitro.     

Changes in the activity of granulocytopoiesis during increasing and reducing the reactions of the lysosomal apparatus of circulating neutrophils in hypovolemic hypotension

An interrelation between the intensity of release of the lysosomal content of circulating neutrophils and the activation degree of granulocytopoiesis and neutrophilia was revealed by means of pharmacological influence on the lysosomal membrane stability in case of hypovolemic hypotension in rabbits. The activation of granulocytopoiesis and neutrophilia increased while intensifying the release of lysosomal factors from the circulating neutrophils and sharply decreased while restricting it. The intensity of hypotension decreased while intensifying the reaction of the lysosomal apparatus of circulating neutrophils and increased while depressing the reaction.     

Rapid Turnover of Glycogen in Memory Formation

The influence of noradrenaline acting at α₂-AR and β₂-ARs on the turnover of glycogen after learning has been investigated. The role of glycogen turnover in memory formation was examined using weakly-reinforced, single trial bead discrimination training in day-old domestic chickens. This study follows our previous work that focused on the need for glycogen breakdown (glycogenolysis) during learning. Inhibition of glycogenolysis by 1,4-dideoxy-1,4-imino-d-arabinitol (DAB) prevented the consolidation of strongly-reinforced learning and inhibited memory. The action of DAB could be prevented by stimulating glycogenolysis with the selective β₂-AR agonist, zinterol. Stimulation of α₂-ARs has been shown to lead to an increase in the turnover and synthesis of glycogen. In the present study, we examined the effect of inhibition of α₂-AR stimulated glycogen turnover (measured as¹⁴C-glucose incorporation into glycogen) on the ability of zinterol to promote the consolidation of weakly reinforced memory. In astrocytes, the selective α₂-AR agonist clonidine stimulated ¹⁴C-glucose incorporation into glycogen in chick astrocytes and this was inhibited by the selective α₂-AR antagonist, ARC239. The critical importance of the timing of ARC239 injection relative to training and intracerebral administration of zinterol was examined. It is concluded that our data provides evidence for a readily accessible labile pool of glycogen in brain astrocytes. If glycogen synthesis is inhibited, the can be depleted within 10?min, thus preventing zinterol from promoting consolidation.     

Functionally relevant neutrophilia in CD11c diphtheria toxin receptor transgenic mice

Transgenic mice expressing the diphtheria toxin receptor (DTR) in specific cell types are key tools for functional studies in several biological systems. B6.FVB-Tg(Itgax-DTR/EGFP)57Lan/J (CD11c.DTR) and B6.Cg-Tg(Itgax-DTR/OVA/EGFP)1Gjh/Crl (CD11c.DOG) mice express the DTR in CD11c(+) cells, allowing conditional depletion of dendritic cells. We report that dendritic-cell depletion in these models caused polymorphonuclear neutrophil (PMN) release from the bone marrow, which caused chemokine-dependent neutrophilia after 6-24 h and increased bacterial clearance in a mouse pyelonephritis model. We present a transgenic mouse line, B6.Cg-Tg(Itgax-EGFP-CRE-DTR-LUC)2Gjh/Crl (CD11c.LuciDTR), which is unaffected by early neutrophilia. However, CD11c.LuciDTR and CD11c.DTR mice showed late neutrophilia 72 h after dendritic cell depletion, which was independent of PMN release and possibly resulted from increased granulopoiesis. Thus, the time point of dendritic cell depletion and the choice of DTR transgenic mouse line must be considered in experimental settings where neutrophils may be involved.