Non-redundant properties of IL-1α and IL-1ß during acute colon inflammation in mice.

OBJECTIVE: The differential role of the IL-1 agonists, IL-1α, which is mainly cell-associated versus IL-1ß, which is mostly secreted, was studied in colon inflammation. DESIGN: Dextran sodium sulfate (DSS) colitis was induced in mice globally deficient in either IL-1α or IL-1ß, and in wild-type mice, or in mice with conditional deletion of IL-1α in intestinal epithelial cells (IECs). Bone marrow transplantation experiments were performed to assess the role of IL-1α or IL-1ß of myeloid versus colon non-hematopoietic cells in inflammation and repair in acute colitis. RESULTS: IL-1α released from damaged IECs acts as an alarmin by initiating and propagating colon inflammation, as IL-1α deficient mice exhibited mild disease symptoms with improved recovery. IL-1ß is involved in repair of IECs and reconstitution of the epithelial barrier during the resolution of colitis; its deficiency correlates with disease exacerbation. Neutralisation of IL-1α in control mice during acute colitis led to alleviation of clinical and histological manifestations, whereas treatment with rIL-1Ra or anti-IL-1ß antibodies was not effective. Repair after colitis correlated with accumulation of CD8 and regulatory T cells in damaged crypts. CONCLUSIONS: The role of IL-1α and IL-1ß differs in DSS-induced colitis in that IL-1α, mainly of colon epithelial cells is inflammatory, whereas IL-1ß, mainly of myeloid cell origin, promotes healing and repair. Given the dissimilar functions of each IL-1 agonistic molecule, an IL-1 receptor blockade would not be as therapeutically effective as specific neutralising of IL-1α, which leaves IL-1ß function intact.

IL-1-induced inflammation promotes development of leishmaniasis in susceptible BALB/c mice.

The role of host-derived IL-1 on the course of Leishmania major infection in susceptible BALB/c mice was assessed. Manifestations of the disease were more severe in mice deficient in the physiological inhibitor of IL-1, the IL-1 receptor antagonist (IL-1Ra) in comparison with control mice. In mice lacking one of the IL-1 genes (IL-1alpha or IL-1beta), there was delayed development of the disease and more attenuated systemic inflammatory responses. IL-1alpha-deficient mice were slightly more resistant to L. major infection compared with IL-1beta-knockout mice. During disease progression in IL-1Ra KO and control mice, myeloid-derived suppressor cells invaded the spleen, concomitant to suppression of T cell-mediated immunity and expression of systemic high levels of pro-inflammatory cytokines. In IL-1-deficient mice, T(h)1 responses were still apparent, even at late stages of the disease. Thus, dose-dependent effects of IL-1 were shown to influence the pathogenesis of murine leishamaniasis in susceptible BALB/c mice. Physiological and supra-physiological levels of IL-1 in the microenvironment promoted an exacerbated form of disease, whereas sub-physiological doses of IL-1 induced a less progressive disease. Thus, manipulation of IL-1 levels in the host, using the IL-1Ra or specific antibodies, has the potential to alleviate symptoms of visceral manifestations of leishmaniasis.

Effects of IL-1 molecules on growth patterns of 3-MCA-induced cell lines: an interplay between immunogenicity and invasive potential.

The balance between inflammation and immunity is cardinal for the outcome of the malignant process. Local attenuated inflammatory responses mediated by innate cells may provide accessory signals for the development of acquired immunity against malignant cells. In contrast, excessive inflammatory responses accompany tumorigenesis and tumor invasiveness, by the induction of immunosuppression. In the present study, we have assessed the role of tumor cell-derived IL-1 in determining the invasive versus immunostimulatory potential of tumor cells. For this purpose, we have used 3-MCA-induced fibrosarcoma cell lines from IL-1 knockout (KO) versus control mice. Cell lines with no IL-1 failed to establish tumors in intact mice, while lines obtained from control mice were invasive and induced a potent angiogenic response. In contrast, cell lines from IL-1KO mice were more immunogenic. SDF-1 and IL-6, each induced by IL-1, were the two major cytokines whose levels differed in cell lines with or without IL-1. We could not detect differences in cell surface markers related to immunogenicity, such as MHC Class I, co-stimulatory, or adhesion molecules between both types of cells. However, more T-cells were observed at the inoculation site of tumor cells devoid of IL-1 and more pronounced parameters related to anti-tumor immunity were observed in the spleen (IL-12 and IFNgamma) of these mice, compared to mice bearing tumors derived from control mice, where host-derived IL-1 is present. In addition, injection of tumor cells devoid of IL-1, which failed to grow in mice, induced an anti-tumor cell immune memory, while in mice injected with tumor cells from control mice; no immune memory could be detected. From the results, it seems that IL-1 is a crucial factor in determining the balance between immunity and inflammation in tumor-bearing mice. This suggests that manipulation of IL-1 could be useful in anti-tumor therapy, by reducing invasiveness and promoting immunity against the malignant cells.

Immune phenomena involved in the in vivo regression of fibrosarcoma cells expressing cell-associated IL-1alpha.

Constitutive expression of cell-associated, but not secreted, interleukin-1alpha (IL-1alpha) by oncogene-transformed fibrosarcoma cells induced regressing tumors in mice, a phenomenon that was abrogated by the IL-1 inhibitor, the IL-1 receptor antagonist (IL-1Ra). On the contrary, non-IL-1alpha-expressing tumor cells induce progressive tumors in mice. In vivo and ex vivo experiments have shown that regression of IL-1alpha-positive fibrosarcoma cells depends on CD8(+) T cells, which can also be activated in CD4(+) T cell-depleted mice, with some contribution of natural killer cells. In spleens of mice bearing the non-IL-1alpha-expressing fibrosarcoma cells, some early and transient manifestations of antitumor-specific immunity, such as activation of specific proliferating T cells, are evident; however, no development of cytolytic T lymphocytes or other antitumor protective cells could be detected. In spleens of mice bearing the non-IL-1alpha-expressing fibrosarcoma cells, the development of early tumor-mediated suppression was observed, and in spleens of mice injected with IL-1alpha-positive fibrosarcoma cells, protective immunity developed in parallel to tumor regression. Treatment of mice bearing violent fibrosarcoma tumors with syngeneic-inactivated, IL-1alpha-positive fibrosarcoma cells, at a critical interval after injection of the malignant cells (Days 5-12), induced tumor regression, possibly by potentiating and amplifying transient antitumor cell immune responses or by ablation of tumor-mediated suppression. Membrane-associated IL-1alpha may thus serve as an adhesion molecule, which allows efficient cell-to-cell interactions between the malignant and immune effector cells that bear IL-1Rs and function as a focused cytokine with adjuvant activities at nontoxic, low levels of expression. Our results also point to the potential of using antitumor immunotherapeutic approaches using cell-associated IL-1alpha.

Interleukin-6 and interleukin-10 are expressed in organs of normal young and old mice.

Interleukin-6 (IL-6) is a pleiotropic inflammatory cytokine, also endowed with inflammation-inhibiting properties. The status of interleukin-10 (IL-10) as an anti-inflammatory cytokine is more solidly established. The roles of IL-6 and IL-10 in the context of organ physiology, and their possible modulation by the aging process, are not satisfactorily understood. The purpose of this work was to characterize organ IL-6 and IL-10 expression in different cellular compartments in mice, under steady-state and stress conditions. The former was evaluated by immunohistochemistry (IHC) and enzyme-linked immunosorbent assay (ELISA) analyses of organ lysates (LYS) (addressing the intracellular compartment), while the latter was assessed by ELISA analyses of organ-conditioned media (CM), obtained after 48 hrs of organ culturing (addressing the potential of cytokine secretion/diffusion). Under steady-state conditions, the overall level of IL-6 and IL-10 expression was relatively low in both age groups (exceptionally, IHC staining demonstrated an enhanced expression of these cytokines in the heart, skeletal muscle and brain of young mice). Much more elevated levels of IL-6 and IL-10 expression were demonstrated in organ CM, possibly emphasizing the role of these cytokines in the context of organ stress. This was most characteristically shown in the highly specialized organs (heart, skeletal muscle and kidney) and liver of old mice, as compared with the other lymphoreticular organs (lungs, spleen, small intestine) tested. Thus, IL-10 was markedly upregulated in the highly specialized organs, while IL-6 was considerably reduced in the lymphoreticular organs. In addition, aging appears to be associated with altered patterns of intracellular expression and secretion/diffusion potentials of IL-6 and IL-10 in the heart and skeletal muscle, as demonstrated by reduced IHC staining on one hand, and an increased detection in organ CM, on the other. These findings may contribute to a better understanding of the unique functions of organ IL-6 and IL-10 in various age groups, and suggest an important role in organ response to stress in old age.

Different patterns of interleukin-1alpha and interleukin-1beta expression in organs of normal young and old mice.

The different physiological roles of interleukin-1alpha (IL-1alpha) and interleukin-1beta (IL-1beta) are not well understood, especially when considering the apparent overlap and redundancy of the two IL-1 molecules. Characterization of IL-1alpha and IL-1beta expression was performed in this study in organs from young and old mice, using immunohistochemistry and ELISA (enzyme-linked immunosorbent assay). The results indicate that organ IL-1alpha and IL-1beta display different patterns of expression: IL-1alpha is manifested more prominently in lymphoreticular organs (lungs, small intestine, spleen, liver), while IL-1beta is more evident in highly specialized and more vulnerable organs, which do not play a leading role in defense against infections and intoxication (heart, brain, skeletal muscle, kidney). This differential expression is more accentuated in old mice, possibly pointing to the special relevance of these cytokines to organ homeostasis in old age. These findings may shed new light on the physiological functions of IL-1alpha and IL-1beta, and may also lead to the development of improved therapeutic approaches, based on the specific manipulation of these cytokines.