[Humanized Mouse Models as a Tool to Study Proinflammatory Cytokine Overexpression].

Dysregulated proinflammatory cytokine expression may result in the development of severe pathologies, such as rheumatoid arthritis, psoriasis, and neurodegenerative diseases. Transgenic mice and, in particular, those with controllable systemic overexpression of proinflammatory cytokines have recently become an essential instrument to study the molecular mechanisms underlying disease development. Importantly, many of the models are humanized by introducing a human cytokine gene, while leaving or removing the respective endogenous mouse gene. Humanized mice are especially valuable for biomedical research as they provide a relevant model to develop therapies based on blocking the pathogenic activity of a cytokine or to establish the functional significance of genome polymorphisms. The review discusses the available humanized mouse models with overexpression of key proinflammatory cytokines (TNF, IL-ip, and IL-6) and inflammatory cytokines with more specific functions (IL-8, IL-17, and IL-32) and their significance for basic and clinical research.

Neonatal Lethality and Inflammatory Phenotype of the New Transgenic Mice with Overexpression of Human Interleukin-6 in Myeloid Cells.

To model human interleukin-6 (hIL-6) associated diseases, unique mice with transgenic overexpression of human IL-6 and reporter fluorescent protein EGFP in cells of macrophage-monocyte lineage were generated using loxP-Cre system. High level of hIL-6 production by macrophages and monocytes, as confirmed in vitro in primary culture of bone marrow-derived macrophages, in vivo resulted in early postnatal death in vivo, presumably, due to the effect of overexpression of hIL-6 on hematopoiesis.

[Proinflammatory and Immunoregulatory Functions of Interleukin 6 as Identified by Reverse Genetics].

Reverse genetics approach, involving genome editing, makes it possible not only to establish the nonredundant and unique functions of genes and their products, but also to construct animal models for biomedical research. Interleukin 6 (IL-6) is an important immunoregulatory and proinflammatory cytokine that differs from many related proteins in having a rather complicated signal transduction scheme. Apart from the multiple functions of IL-6, the most relevant biological problem of recent years was establishing what cells produce IL-6, in what form IL-6 is produced, what cells are recipients of the IL-6 signal, and what are the downstream events and physiological consequences of the IL-6 signaling cascade. Because IL-6 is involved in the pathogenesis of many diseases and is a drug target, understanding the mechanisms of its normal and pathogenic effects is important for the clinics. The review summarizes the recent data available in the field.

Effects of Fibroin Microcarriers on Inflammation and Regeneration of Deep Skin Wounds in Mice.

The process of tissue regeneration following damage takes place with direct participation of the immune system. The use of biomaterials as scaffolds to facilitate healing of skin wounds is a new and interesting area of regenerative medicine and biomedical research. In many ways, the regenerative potential of biological material is related to its ability to modulate the inflammatory response. At the same time, all foreign materials, once implanted into a living tissue, to varying degree cause an immune reaction. The modern approach to the development of bioengineered structures for applications in regenerative medicine should be directed toward using the properties of the inflammatory response that improve healing, but do not lead to negative chronic manifestations. In this work, we studied the effect of microcarriers comprised of either fibroin or fibroin supplemented with gelatin on the dynamics of the healing, as well as inflammation, during regeneration of deep skin wounds in mice. We found that subcutaneous administration of microcarriers to the wound area resulted in uniform contraction of the wounds in mice in our experimental model, and microcarrier particles induced the infiltration of immune cells. This was associated with increased expression of proinflammatory cytokines TNF, IL-6, IL-1ß, and chemokines CXCL1 and CXCL2, which contributed to full functional recovery of the injured area and the absence of fibrosis as compared to the control group.

Formation of compact aggregates of B-lymphocytes in lung tissue during mycobacterial infection in mice depends on TNF production by these cells and is not an element of the host's immunological protection.

Tumor necrosis factor (TNF) plays a pivotal role in the early control of Mycobacterium tuberculosis and M. avium infections by a host. It was previously shown that both phagocyte-derived and T-cell-derived TNF productions are critical for protective immunity against M. tuberculosis, but the role of TNF produced by B-cells remained unclear. By comparing mice with B-cell-specific TNF deletion to littermate control mice, here we show that TNF production by B-lymphocytes is essential for the formation of infection-specific aggregates of B-cells in the lung. It is likely that these compact foci represent a pathogenic feature of inflammatory response rather than an element of protective immunity, since the capacity to form aggregates has no influence on the severity of M. tuberculosis- and M. avium-triggered diseases.

Experimental models of arthritis in which pathogenesis is dependent on TNF expression.

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease characterized by joint damage as well as systemic manifestations. The exact cause of RA is not known. Both genetic and environmental factors are believed to contribute to the development of this disease. Increased expression of tumor necrosis factor (TNF) has been implicated in the pathogenesis of RA. Currently, the use of anti-TNF drugs is one of the most effective strategies for the treatment of RA, although therapeutic response is not observed in all patients. Furthermore, due to non-redundant protective functions of TNF, systemic anti-TNF therapy is often associated with unwanted side effects such as increased frequency of infectious diseases. Development of experimental models of arthritis in mice is necessary for studies on the mechanisms of pathogenesis of this disease and can be useful for comparative evaluation of various anti-TNF drugs. Here we provide an overview of the field and present our own data with two experimental models of autoimmune arthritis - collagen-induced arthritis and antibody-induced arthritis in C57Bl/6 and BALB/c mice, as well as in tnf-humanized mice generated on C57Bl/6 background. We show that TNF-deficient mice are resistant to the development of collagen-induced arthritis, and the use of anti-TNF therapy significantly reduces the disease symptoms. We also generated and evaluated a fluorescent detector of TNF overexpression in vivo. Overall, we have developed an experimental platform for studying the mechanisms of action of existing and newly developed anti-TNF drugs for the treatment of rheumatoid arthritis.

Mouse lymphomyeloid cells can function with significantly decreased expression levels of cytochrome C.

Cytochrome c is an indispensable electron carrier in the mitochondrial respiratory chain and also an important mediator of the internal pathway triggering apoptosis. Mice with a complete deficiency of the Cycs gene encoding the somatic cytochrome c die during the embryogenesis. Using the technology of LoxP-cre-dependent tissue-specific recombination, we obtained some mouse strains with significantly reduced expression of cytochrome c in certain cell types ("conditional genetic knockdown"). This knockdown was achieved by abrogation of the normal splicing of the Cycs locus pre-mRNA due to an additional acceptor site inside the stop-cassette neo(r). Previously, we observed embryonic lethality in homozygous mice with the same knockdown of cytochrome c in all cells of the organism. In the present work we studied two novel mouse strains with conditional knockdown of the Cycs gene in T lymphocytes and macrophages. Somewhat surprisingly, the mice of these two strains under normal conditions were not phenotypically different from the wild-type mice, either on the whole organism level or on the level of activity of individual target cells. Thus, the amount of cytochrome c in lymphomyeloid cells does not affect their development and normal functioning.

[Multidirectional effect of MIF and sodium polyprenyl phosphate on the course of experimental flavivirus infection in mice].

AIM: Study of macrophage migration inhibiting factor (MIF) effect after intracerebral administration on the course of experimental infection induced in mice by tick borne encephalitis virus (TEV), and study of sodium polyprenyl phosphate (PPP) and/or antibodies against MIF on the course of this infection against the background of MIF administration. MATERIALS AND METHODS: Phosprenil preparation was used as a source of PPP. PPP was administered intracerebrally. MIF--human recombinant (R&D, USA), mice--Balb/c line. RESULTS: In the sera of mice infected with TEV, MIF production stimulation was detected at days 8 through 10 after the infection--against the background of clinical signs presentation of tick borne encephalitis (TE). Administration of PPP to infected mice, on the contrary, resulted in MIF production suppression at the specified period. After administration of 20 ng of MIF to mice, lethality increased by 40% and average life span decreased by 2.3 days. Thus, MIF at high doses caused an increase of infection course severity, induced by TEV in mice, and administration of 60 microg of PPP resulted in the protection from infection in 100% of cases. Intracerebral administrationto mice of antibodies against MIF resulted in a decrease of lethality indicator up to 26% as compared with control and an increase of averagelife span by 5.5 days. During simultaneous administration into the brain of infected mice of MIF, PPP and antibodies against MIF, prevention of MIF-induced increase of TE course severity was registered. CONCLUSION: The data obtained allow to conclude that MIF may serve as an indicator of TE course severity, and possible prognostic indicator of meningo-encephalitic form development in humans.