Whole-Body In Vivo Monitoring of Inflammatory Diseases Exploiting Human Interleukin 6-Luciferase Transgenic Mice

Abstract

Chronic inflammation underlies the pathological progression of various diseases, and thus many efforts have been made to quantitatively evaluate the inflammatory status of the diseases. In this study, we generated a highly sensitive inflammation-monitoring mouse system using a bacterial artificial chromosome (BAC) clone containing extended flanking sequences of the human interleukin 6 gene (hIL6) locus, in which the luciferase (Luc) reporter gene is integrated (hIL6-BAC-Luc). We successfully monitored lipopolysaccharide-induced systemic inflammation in various tissues of the hIL6-BAC-Luc mice using an in vivo bioluminescence imaging system. When two chronic inflammatory disease models, i.e., a genetic model of atopic dermatitis and a model of experimental autoimmune encephalomyelitis (EAE), were applied to the hIL6-BAC-Luc mice, luciferase bioluminescence was specifically detected in the atopic skin lesion and central nervous system, respectively. Moreover, the Luc activities correlated well with the disease severity. Nrf2 is a master transcription factor that regulates antioxidative and detoxification enzyme genes. Upon EAE induction, the Nrf2-deficient mice crossed with the hIL6-BAC-Luc mice exhibited enhanced neurological symptoms concomitantly with robust luciferase luminescence in the neuronal tissue. Thus, whole-body in vivo monitoring using the hIL6-BAC-Luc transgenic system (WIM-6 system) provides a new and powerful diagnostic tool for real-time in vivo monitoring of inflammatory status in multiple different disease models. E xposure to environmental xenobiotics and the accompanying production of cellular oxidative stress give rise to a wide variety of inflammatory diseases in modern society (reviewed in references 1 and 2). To take a step against the widespread prevalence of inflammation-related diseases or low-grade systemic inflammations, it is crucial to elucidate the mechanistic basis for the cellular response to the inflammation. In this aspect, development of an in vivo monitoring system for evaluation of inflammatory status and validation of therapeutic agents has been eagerly awaited. Accurate and sensitive inflammation-monitoring animal models will accelerate further study of inflammatory diseases and development of new therapeutics.Inflammatory stimuli induce gene expression of a series of proinflammatory cytokines, such as tumor necrosis factor (TNF), interleukin 1␤ (IL-1␤), and IL-6. Among the proinflammatory cytokines, IL-6 is a key cytokine that is produced by many types of cells, including immune cells (e.g., macrophages and T and B lymphocytes), hepatocytes, glial cells, and fibroblasts (reviewed in reference 3). Expression of IL-6 in resting immune cells is usually suppressed, while it is rapidly induced upon exposure to a variety of inflammatory stimuli (reviewed in reference 4). Subsequently, the induced IL-6 participates in multiple physiological and pathological processes, including innate and acquired immune responses and pathogenesis of autoimmune inflammatory diseases. This sensi...

Amelioration of inflammation and tissue damage in sickle cell model mice by Nrf2 activation

“…2A). To monitor the inflammation status of multiple tissues in vivo, we used an IL-6 reporter mouse system referred to as "the whole-body in vivo monitoring with the hIL6-BAC-Luc transgenic system (WIM-6 system)" (27). This reporter enables the direct detection of inflammation status in vivo by monitoring a luciferase reporter gene expressed under the control of the human IL6 gene.…”

“…SCD model mice (23) and Keap1 hypomorphic mutant (Keap1 F/− ) (24-26) mice were described previously. WIM-6 mice were described in our paper (27 Immunoblot Analysis. Nuclear fraction was prepared from liver and lung using NE-PER nuclear and cytoplasmic extraction reagents (Thermo Scientific) according to the manufacturer's instructions.…”

Animal models of multiple sclerosis: Focus on experimental autoimmune encephalomyelitis

“…The expression of firefly luciferase under promoters of different genes enabled monitoring of the processes that involve the target molecule in living mice. This model was proposed to be a functional and valuable tool for monitoring whole‐body in vivo inflammation in various disease models including EAE (Hayashi et al, ; Li et al, ; Yang et al, ). Moreover, bioluminescence imaging was used to track the transplanted human embryonic stem cell–derived oligodendrocyte progenitors and neural stem cells during EAE (Ayzenberg et al, ; Stefferl, Brehm, et al, ).…”

“…Moreover, bioluminescence imaging was used to track the transplanted human embryonic stem cell–derived oligodendrocyte progenitors and neural stem cells during EAE (Ayzenberg et al, ; Stefferl, Brehm, et al, ). By expressing firefly luciferase under the IL‐6 promoter, Hayashi et al were able to show bioluminescence in the spinal cord and brain in the EAE mice (Hayashi et al, ). Similarly, mice with luciferase firefly expressed under a c‐Rel promoter showed bioluminescence in the spinal cord even before the onset of EAE, indicating that reporter animals could be a valuable tool for monitoring early events in EAE development (Yang et al, ).…”

HSC Aging and Senescent Immune Remodeling

“…Age-related alterations in innate immunity are often associated with high levels of inflammation, often referred to as inflammaging. Clinically, inflammaging can be a major contributor to aging-associated disease in non-hematopoietic tissues [17, 18]. …”