Human CXCR2 (hCXCR2) takes over functionalities of its murine homolog in hCXCR2 knockin mice

Abstract

Human CXCR2 (hCXCR2) has been implicated in diverse inflammatory diseases. When roles of this receptor studied in animal models are extrapolated into men, large species differences in expression of the receptor and its ligands must be considered. These differences seriously weaken conclusions toward the role of hCXCR2 in the development of human diseases. It furthermore hampers straightforward testing of CXCR2 antagonists, especially when compounds discriminate between human and other species' receptors. Using gene targeting in embryonic stem cells, a hCXCR2 knockin mouse strain was generated in which endogenous murine CXCR2 (mCXCR2) sequences are replaced by the hCXCR2 gene. Correct targeting and expression on neutrophils were confirmed by Southern blot and immunohistochemical analyses. A phenotypic analysis of the hCXCR2 knockin mice, in comparison to wild-type and CXCR2 knockout mice, confirmed proper function of the hCXCR2 gene. In vivo migratory responses of neutrophils were intact in hCXCR2 knockin mice. Finally, an experiment with a CXCR2 antagonist demonstrated that the knockin model is indeed useful for in vivo evaluation of low-molecular weight compounds. In conclusion, our data unequivocally show that hCXCR2 can functionally replace mCXCR2, making this an attractive model to test novel pharmaceuticals designed to antagonize human CXCR2 in vivo.

Chronic Interleukin-1β Expression in Mouse Brain Leads to Leukocyte Infiltration and Neutrophil-Independent Blood–Brain Barrier Permeability without Overt Neurodegeneration

“…4 A). CXCR2 is most highly expressed by neutrophils in mice, and was therefore used as a surrogate marker for the presence of neutrophils in the hippocampus (Mihara et al, 2005). Indeed, neutrophil infiltration mirrored significant induction of CXCR2 gene transcripts (Fig.…”

Using guinea pigs in studies relevant to asthma and COPD

“…Moreover, the beta adrenoceptors mediating airway smooth muscle relaxation in mice are the beta 1 subtype, not the beta 2 subtype as it is entirely in human and primarily in guinea pig airways [259]. Receptor agonist and antagonist potency and efficacy in rats and mice are also known to differ from that in humans, prompting some researchers to develop transgenic mice expressing human receptors [260][261][262][263][264][265][266][267][268][269][270]. This renders the mouse of limited utility in preclinical studies of many classes of therapeutic interventions designed for treating asthma and COPD.…”

Functional Replacement of Murine CXCR2 by Its Human Homologue in the Development of Atherosclerosis in LDLR Knockout Mice

“…The hCXR2(Ϫ/Ϫ) mice were generated as previously described. 5) Animals were housed in macrolon cages (eight animals/cage) at 19-21°C; the relative humidity was 50-60%, and an artificial light cycle of 12 h alternating with 12 h darkness was offered. Standard pelleted food (SDS; Special Diet Services, Witham, U.K.) or high-cholesterol atherogenic diet (Harlan Teklad #94059) and water was provided ad libitum.…”

“…The hCXCR2(ϩ/ϩ) mice as previously generated 5) were mated with the LDLR(Ϫ/Ϫ) mice and tails of offspring were used for PCR genotyping. The primers to identify the mCXCR2 (5Ј-GCTCTGGCATGCCCTCTATTC-3Ј and 5Ј-GTCCATG-CTGATGCAGGCTA-3Ј), hCXCR2 (5Ј-CCCATGTGAAC-CAGAATCCC-3Ј and 5Ј-TCCGCCAGTTTGCTGTATTG-3Ј), LDLR (5Ј-TTGTGTGTGATGGAGACCGAG-3Ј and 5Ј-GCCGTCAACACAGTCGACAT-3Ј) and LDLR(Ϫ/Ϫ)(5Ј-GATTGGGAAGACAATAGCAGGCATGC-3Ј and 5Ј-GGC-AAGATGGCTCAGCAAGCAAAGGC-3Ј) were used.…”

“…2,4) We have previously generated hCXCR2 knockin (hCXCR2(ϩ/ϩ)) mice that carry hCXCR2 instead of its mouse homolog, and described the full characterization of this knockin model. 5) The phenotype of the hCXCR2(ϩ/ϩ) mouse in contrast to mCXCR2 knockout mice perfectly resembled that of wild-type mice, indicating that the hCXCR2 is capable of functionally replacing its mouse counterpart. One of the most potential advantages of generating this model is that it allows one to study the role of hCXCR2 in the development of diseases like atherosclerosis, rheumatoid arthritis and psoriasis in preclinical animal studies using either antibodies against hCXCR2 or human specific CXCR2 antagonists.…”