Interleukin-6 is not essential for bone turnover in hypothyroid mice

Interleukin-6 (IL-6) has been shown to be involved in the pathogenesis of several bone diseases characterized by an imbalance between bone resorption and formation. The aim of the study was to estimate serum markers of bone turnover: osteoclast-derived tartrate-resistant acid phosphatase form 5a (TRACP 5b) and osteocalcin in IL-6-deficient mice to assess the role of IL-6 in bone metabolism in hypothyroidism in mice. C57BL/6J (wild-type; WT) and C57BL/6J(IL6-/-Kopf) (IL-6 knock-out; IL6KO) mice randomly divided into 4 groups with 10 in each one: 1/ WT mice in hypothyroidism (WT-ht), 2/ WT controls, 3/ IL6KO mice with hypothyroidism (IL6KO-ht) and 4/ IL6KO controls. Experimental model of hypothyroidism was induced by intraperitoneal injection of propylthiouracyl. The serum levels of TRACP 5b and osteocalcin were determined by ELISA. Serum concentrations of TRACP 5b (median and interquartile ranges) were significantly decreased in both groups of mice with hypothyroidism: WT (3.2 (2.5-4.7) U/l) and IL6KO (2.6 (1.8-3.5) U/l) as compared to the respective controls. Similarly, serum osteocalcin levels were significantly reduced in both groups of mice in experimental hypothyroidism: WT (25.8 (23.0-28.2) ng/ml) and IL6KO (21.5(19.0-24.6) ng/ml) in comparison to the respective controls. There were no significant differences in bone turnover markers between IL6KO and WT mice both in hypothyroid and control animals. The results of the present study suggest that IL-6 does not play an important role in bone turnover in both euthyroid and hypothyroid mice.     

A crucial role of interleukin-6 in the pathogenesis of thyrotoxicosis-related disturbances of bone turnover in mice.

Interleukin-6 (IL-6) has been shown to be involved in the pathogenesis of several bone diseases characterized by a negative balance between bone resorption and formation. The aim of the study was to estimate serum markers of bone turnover: osteoclast-derived tartrate-resistant acid phosphatase form 5a (TRACP 5b) reflecting resorption, and osteocalcin as a marker of bone formation in IL-6 knock-out mice to assess the role of IL-6 in the pathogenesis of thyrotoxicosis-related disturbances of bone metabolism. The study was performed on forty, 14-15 weeks old, female mice: C57BL/6J (wild-type; WT) and C57BL/6J (IL6-/-Kopf) (IL-6 knock-out; IL6KO). The mice were randomly divided into 4 groups with 10 mice in each one: 1. WT mice in thyrotoxicosis (WT-thx), 2. WT controls (WT-ctrl), 3. IL6KO mice with thyrotoxicosis (IL6KO-thx), and 4. IL6KO controls. Experimental model of hyperthyroidism was induced by intraperitoneal injection of levothyroxine at a dose of 1 microg/g, daily over 21 days. The serum levels of TRACP 5b and osteocalcin were determined by ELISA. Serum concentration of TRACP 5b (median and interquartile ranges) were significantly increased in both groups of mice with thyrotoxicosis: WT [28.2(18.8-41.6) U/l] and IL6KO [26.4(23.0-31.2) U/l] as compared to the respective controls. Osteocalcin serum levels in IL6KO-thx mice [111.9(103.1-175.6) ng/ml] were significantly elevated in comparison to WT-thx animals [46.1(32.5-58.9) ng/ml]. In summary, the results of the present study suggest that IL-6 plays a crucial role in thyrotoxicosis-related disturbances of bone turnover in mice, determining the imbalance between bone resorption and bone formation caused by excess of thyroid hormones predominantly by inhibition of bone formation.     

Invariant NKT cell defects in vitamin D receptor knockout mice prevents experimental lung inflammation

Vitamin D receptor (VDR) deficiency (knockout [KO]) results in a failure of mice to generate an airway hyperreactivity (AHR) response on both the BALB/c and C57BL/6 background. The cause of the failed AHR response is the defective population of invariant NKT (iNKT) cells in the VDR KO mice because wild-type (WT) iNKT cells rescued the AHR response. VDR KO mice had significantly fewer iNKT cells and normal numbers of T cells in the spleen compared with WT mice. In BALB/c VDR KO mice, the reduced frequencies of iNKT cells were not apparent in the liver or thymus. VDR KO and WT Th2 cells produced similar levels of IFN-γ and IL-5. On the BALB/c background, Th2 cells from VDR KO mice produced less IL-13, whereas on the C57BL/6 background, Th2 cells from VDR KO mice produced less IL-4. Conversely, VDR KO iNKT cells were defective for the production of multiple cytokines (BALB/c: IL-4, IL-5, and IL-13; C57BL/6: IL-4 and IL-17). Despite relatively normal Th2 responses, BALB/c and C57BL/6 VDR KO mice failed to develop AHR responses. The defect in iNKT cells as a result of the VDR KO was more important than the highly susceptible Th2 background of the BALB/c mice. Defective iNKT cell responses in the absence of the VDR result in the failure to generate AHR responses in the lung. The implication of these mechanistic findings for human asthma requires further investigation.     

Interferon-gamma is required for the late but not early control of Leishmania amazonensis infection in C57Bl/6 mice

The critical role of interferon-gamma (IFN-gamma) in the resistance of C57Bl/6 mice to Leishmania major is widely established but its role in the relative resistance of these animals to L. amazonensis infection is still not clear. In this work we use C57Bl/6 mice congenitally deficient in the IFN-gamma gene (IFN-gamma KO) to address this issue. We found that IFN-gamma KO mice were as resistant as their wild-type (WT) counterparts at least during the first two months of infection. Afterwards, whereas WT mice maintained lesion growth under control, IFN-gamma KO mice developed devastating lesions. At day 97 of infection, their lesions were 9-fold larger than WT controls, concomitant with an increased parasite burden. At this stage, lesion-draining cells from IFN-gamma KO mice had impaired capacity to produce interleukin-12 (IL-12) and tumour necrosis factor-a in response to parasite antigens whereas IL-4 was slightly increased in comparison to infected WT mice. Together, these results show that IFN-gamma is not critical for the initial control of L. amazonensis infection in C57Bl/6 mice, but is essential for the development of a protective Th1 type immune response in the later stages.     

Prolonged renal allograft survival by donor interleukin-6 deficiency: association with decreased alloantibodies and increased intragraft T regulatory cells

Both humoral and cellular immune responses are involved in renal allograft rejection. Interleukin (IL)-6 is a regulatory cytokine for both B and Foxp3 (forkhead box P3)-expressing regulatory T (Treg) cells. This study was designed to investigate the impact of donor IL-6 production on renal allograft survival. Donor kidneys from IL-6 knockout (KO) vs. wild-type (WT) C57BL/6 mice (H-2(b)) were orthotopically transplanted to nephrotomized BALB/c mice (H-2(d)). Alloantibodies and Treg cells were examined by fluorescence-activated cell sorting analysis. Graft survival was determined by the time to graft failure. Here, we showed that a deficiency in IL-6 expression in donor kidneys significantly prolonged renal allograft survival compared with WT controls. IL-6 protein was upregulated in renal tubules and endothelium of renal allografts following rejection, which correlated with an increase in serum IL-6 compared with that in those receiving KO grafts or naive controls. The absence of graft-producing IL-6 or lower levels of serum IL-6 in the recipients receiving IL-6 KO allografts was associated with decreased circulating anti-graft alloantibodies and increased the percentage of intragraft CD4(+)CD25(+)Foxp3(+) Treg cells compared with those with WT allografts. In conclusion, the lack of graft-producing IL-6 significantly prolongs renal allograft survival, which is associated with reduced alloantibody production and/or increased intragraft Treg cell population, implying that targeting donor IL-6 may effectively prevent both humoral and cellular rejection of kidney transplants.     

Diurnal variation of heart rate, locomotor activity, and body temperature in interleukin-1 alpha/beta doubly deficient mice.

This study was investigated the roles of interleukin-1 (IL-1) on diurnal rhythms of heart rate (HR), locomotor activity (LA), and body temperature (BT). For this purpose, HR, LA, and BT were recorded from conscious and unrestrained IL-1 alpha/beta doubly deficient (KO) and normal C57BL/6J mice using a telemetry system. These parameters were continuously recorded from just after to 2 weeks after transmitter implantation, because we thought that the surgical stress-induced IL-1 might affect the biobehavioral activities of the animals. At 1 day after implantation, HR and LA in IL-1 alpha/beta KO mice were higher than those in C57BL/6J mice. While BT in IL-1 alpha/beta KO mice was lower than that in C57BL/6J mice. Moreover, diurnal rhythmicity in these parameters after implantation in IL-1 alpha/beta KO mice appeared earlier than in C57BL/6J mice. At 2 weeks after implantation, there were no significant differences in the light- and dark-phase values of each parameter between IL-1 alpha/beta KO and C57BL/6J mice, however, IL-1 alpha/beta KO mice showed clear ultradian rhythmicity. It is thought that a phenotypical difference in biobehavioral activities between IL-1 alpha/beta KO and C57BL/6J mice may reflect IL-1 induced febrile and behavioral responses. These results suggest that IL-1 may play important physiological and pathophysiological roles on biobehavioral activities.     

Bleomycin-induced lung fibrosis in IL-4-overexpressing and knockout mice

The role of IL-4 in the development of lung fibrosis is as yet unclear. Bleomycin (Bleo) or saline (Sal) was injected intratracheally into three groups of C57BL/6J mice: transgenic animals that overexpressed IL-4 (IL-4 TG, n = 14), mice with a targeted knockout mutation of the IL-4 gene (IL-4 KO, n = 11), and wild-type (WT, n = 13) mice. At 14 days, lung fibrosis was evaluated by hydroxyproline measurement and by quantitative image analysis of fibrosis fraction and alveolar wall area fraction. Bronchoalveolar lavage cell counts in all Bleo-treated groups demonstrated an increased percentage of lymphocytes with a corresponding decrease in the percentage of macrophages. Comparing Bleo- to Sal-treated controls within each group of mice showed increases in all lung fibrosis parameters in IL-4 KO and WT, but not in any of the parameters in IL-4 TG mice. The severity of Bleo-induced fibrotic response was decreased in overexpressed IL-4 TG compared with IL-4 KO mice. These data negate a critical profibrotic role for IL-4 in Bleo-induced lung fibrosis.     

Abrogated RANKL expression in properdin-deficient mice is associated with better outcome from collagen-antibody-induced arthritis

Introduction

Properdin amplifies the alternative pathway of complement activation. In the present study, we evaluated its role in the development of collagen antibody-induced arthritis (CAIA).

Methods

Arthritis was induced by intraperitoneal injection of a collagen antibody cocktail into properdin-deficient (KO) and wild-type (WT) C57BL/6 mice. Symptoms of disease were evaluated daily. The degree of joint damage was assessed histologically and with immunostaining for bone-resorption markers. Phenotypes of cell populations, their receptor expression, and intracellular cytokine production were determined with flow cytometry. Osteoclast differentiation of bone marrow (BM) precursors was evaluated by staining for tartrate-resistant acid phosphatase (TRAP).

Results

Properdin-deficient mice developed less severe CAIA than did WT mice. They showed significantly improved clinical scores and downregulated expression of bone-resorption markers in the joints at day 10 of disease. The frequencies of Ly6G⁺CD11b⁺ cells were fewer in BM, blood, and synovial fluid (SF) of KO than of WT CAIA mice. The receptor activator of nuclear factor κB ligand (RANKL) was downregulated on arthritic KO neutrophils from BM and the periphery. Decreased C5a amounts in KO SF contributed to lower frequencies of CD5aR⁺-bearing neutrophils. In blood, surface C5aR was detected on KO Ly6G⁺ cells as a result of low receptor engagement. Circulating CD4⁺ T cells had an altered ability to produce interleukin (IL)-17 and interferon (IFN)-γ and to express RANKL. In KO CAIA mice, decreased frequencies of CD4⁺ T cells in the spleen were related to low CD86 expression on Ly6G^highCD11b⁺ cells. Arthritic KO T cells spontaneously secreted IFN-γ but not IL-17 and IL-6, and responded to restimulation with less-vigorous cytokine production in comparison to WT cells. Fewer TRAP-positive mature osteoclasts were found in KO BM cell cultures.

Conclusions

Our data show that the active involvement of properdin in arthritis is related to an increased proinflammatory cytokine production and RANKL expression on immune cells and to a stimulation of the RANKL-dependent osteoclast differentiation.     

CD4+ Th1 and CD8+ type 1 cytotoxic T cells both play a crucial role in the full development of contact hypersensitivity

The role of CD4(+) vs CD8(+) T cells in contact hypersensitivity (CHS) remains controversial. In this study, we used gene knockout (KO) mice deficient in CD4(+) or CD8(+) T cells to directly address this issue. Mice lacking either CD4(+) or CD8(+) T cells demonstrated depressed CHS responses to dinitrofluorobenzene and oxazolone compared with wild-type C57BL/6 mice. The depression of CHS was more significant in CD8 KO mice than in CD4 KO mice. Furthermore, in vivo depletion of either CD8(+) T cells from CD4 KO mice or CD4(+) T cells from CD8 KO mice virtually abolished CHS responses. Lymph node cells (LNCs) from hapten-sensitized CD4 and CD8 KO mice showed a decreased capacity for transferring CHS. In vitro depletion of either CD4(+) T cells from CD8 KO LNCs or CD8(+) T cells from CD4 KO LNCs resulted in a complete loss of CHS transfer. LNCs from CD4 and CD8 KO mice produced significant amounts of IFN-gamma, indicating that both CD4(+) and CD8(+) T cells are able to secrete IFN-gamma. LNCs from CD8, but not CD4, KO mice were able to produce IL-4 and IL-10, suggesting that IL-4 and IL-10 are mainly derived from CD4(+) T cells. Intracellular cytokine staining of LNCs confirmed that IFN-gamma-positive cells consisted of CD4(+) (Th1) and CD8(+) (type 1 cytotoxic T) T cells, whereas IL-10-positive cells were exclusively CD4(+) (Th2) T cells. Collectively, these results suggest that both CD4(+) Th1 and CD8(+) type 1 cytotoxic T cells are crucial effector cells in CHS responses to dinitrofluorobenzene and oxazolone in C57BL/6 mice.     

IL-6 is essential for development of gut barrier dysfunction after hemorrhagic shock and resuscitation in mice

We sought to determine the role of IL-6 as a mediator of the alterations in gut barrier function that occur after hemorrhagic shock and resuscitation (HS/R). C57Bl/6 wild-type (WT) and IL-6 knockout (KO) mice on a C57Bl/6 background were subjected to either a sham procedure or HS/R. Organ and tissue samples were obtained 4 h after resuscitation. In WT mice, HS/R significantly increased ileal mucosal permeability to fluorescein isothiocyanate-labeled dextran (average molecular mass, 4 kDa) and bacterial translocation to mesenteric lymph nodes. These alterations in gut barrier function were not observed in IL-6 KO animals. HS/R increased ileal steady-state mRNA levels for IL-6, TNF, and IL-10 in WT but not in IL-6 KO mice. Ileal mucosal expression of the tight junction protein, ZO-1, decreased after HS/R in WT but not IL-6 KO mice. Collectively, these data support the view that expression of IL-6 is essential for the development of gut barrier dysfunction after HS/R.     

CD44-deficient mice exhibit enhanced hepatitis after concanavalin A injection: evidence for involvement of CD44 in activation-induced cell death

Administration of Con A induces severe injury to hepatocytes in mice and is considered to be a model for human hepatitis. In the current study, we investigated the role of CD44 in Con A-induced hepatitis. Intravenous administration of Con A (20 mg/kg) caused 100% mortality in C57BL/6 CD44-knockout (KO) mice, although it was not lethal in C57BL/6 CD44 wild-type (WT) mice. Administration of lower doses of Con A (12 mg/kg body weight) into CD44 WT mice induced hepatitis as evident from increased plasma aspartate aminotransferase levels accompanied by active infiltration of mononuclear cells and neutrophils, and significant induction of apoptosis in the liver. Interestingly, CD44 KO mice injected with similar doses of Con A exhibited more severe acute suppurative hepatitis. Transfer of spleen cells from Con A-injected CD44 KO mice into CD44 WT mice induced higher levels of hepatitis when compared with transfer of similar cells from CD44 WT mice into CD44 WT mice. The increased hepatitis seen in CD44 KO mice was accompanied by increased production of cytokines such as TNF-alpha, IL-2 and IFN-gamma, but not Fas or Fas ligand. The increased susceptibility of CD44 KO mice to hepatitis correlated with the observation that T cells from CD44 KO mice were more resistant to activation-induced cell death when compared with the CD44 WT mice. Together, these data demonstrate that activated T cells use CD44 to undergo apoptosis, and dysregulation in this pathway could lead to increased pathogenesis in a number of diseases, including hepatitis.     

Genetic Difference of Hypothyroidism-Induced Cognitive Dysfunction in C57BL/6j and 129/Sv Mice

Adult-onset hypothyroidism induces cognitive impairments in learning and memory. Thyroxin (T4) replacement therapy appears to be effective in biochemically restoring euthyroidism, as evidenced by serum T4 and triiodothyronine concentrations within the normal range, although some the patients still exhibit cognitive dysfunctions. Here, we investigated the cognitive functions of propylthiouracil-induced hypothyroid mice in C57BL/6j and 129/Sv strains using the passive avoidance task and the novel object recognition test. Cognitive dysfunctions in hypothyroid mice were found only in the C57BL/6j strain, not in the 129/Sv strain. Further, we found that cholinergic neurons in the basal forebrain increased the membrane potential and input resistance with decreased capacitance, and that they decreased the amplitude and width of action potential in hypothyroid mice in the C57BL/6j strain but not in those in the 129/Sv strain, compared with the controls for each strain. Additionally, the excitability of cholinergic neurons in the basal forebrain was reduced in the hypothyroid mice in the C57BL/6j strain. These results indicated that transgenic mice with the C57BL/6j genetic background are more suitable for revealing the mechanism underlying hypothyroidism-induced cognitive dysfunction, and that the cholinergic basal forebrain may be the appropriate target for treating cognitive dysfunction in adult-onset hypothyroidism.

     

IL-23 is critical in the induction but not in the effector phase of experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE), a T cell-mediated inflammatory disease of the CNS, is a rodent model of human multiple sclerosis. IL-23 is one of the critical cytokines in EAE development and is currently believed to be involved in the maintenance of encephalitogenic responses during the tissue damage effector phase of the disease. In this study, we show that encephalitogenic T cells from myelin oligodendrocyte glycopeptide (MOG)-immunized wild-type (WT) mice caused indistinguishable disease when adoptively transferred to WT or IL-23-deficient (p19 knockout (KO)) recipient mice, demonstrating that once encephalitogenic cells have been generated, EAE can develop in the complete absence of IL-23. Furthermore, IL-12/23 double-deficient (p35/p19 double KO) recipient mice developed EAE that was indistinguishable from WT recipients, indicating that IL-12 did not compensate for IL-23 deficiency during the effector phase of EAE. In contrast, MOG-specific T cells from p19KO mice induced EAE with delayed onset and much lower severity when transferred to WT recipient mice as compared with the EAE that was induced by cells from WT controls. MOG-specific T cells from p19KO mice were highly deficient in the production of IFN-gamma, IL-17A, and TNF, indicating that IL-23 plays a critical role in development of encephalitogenic T cells and facilitates the development of T cells toward both Th1 and Th17 pathways.     

IL-6 KO mice develop experimental amoebic liver infection with eosinophilia

Interleukin 6 (IL-6) is a multifunctional cytokine that regulates various aspects of the immune response, such as acute phase reaction and hematopoiesis, and is an important signal that coordinates activities of liver cells, macrophages, and lymphocytes. Amoebic liver lesions have been studied, usually in hamsters, due to the problem of abscess development in mice. We report here the development of an experimental amoebic liver abscess (ALA) model in mice deficient in IL-6. Axenically grown amoebae were injected directly into the livers of C57BL/6 wild type (WT) and IL-6 KO -/- mice; the abscesses produced were counted and the inflammatory process was examined on 5, 10, and 20 days postinfection. Our results showed that IL-6 KO -/- mice develop ALA, in contrast to the WT strain, which usually do not have signs of abscess or infection. Histological analysis of the abscesses showed extended inflammatory response, mainly mediated by eosinophils, which strongly infiltrate the abscess in IL-6 K -/- mice. The present results suggest that in mice, IL-6 could play a role in the resistance against ALA.     

Role of phosphatidylinositol-3-kinase-gamma (PI3Kgamma)-mediated pathway in 17beta-estradiol-induced killing of L. mexicana in macrophages from C57BL/6 mice

We recently demonstrated that 17beta-estradiol (E2) enhances killing of Leishmania mexicana in macrophages from both male and female DBA/2 mouse by increasing nitric oxide (NO) production. Here, we analyzed the effect of E2 on leishmanicidal activity and cytokine production by bone marrow-derived macrophages (BMDMs) from male and female C57BL/6 mice in vitro, specifically examining the role of phosphatidylinositol-3-kinase-gamma (PI3Kgamma) in E2-induced parasite killing. Unlike its effect on macrophages from both male and female DBA/2 mice, E2 only increased leishmanicidal activity in macrophages from female C57BL/6 mice, which was evident by a significant reduction in both infection rates and infection levels compared to sham controls. E2-treated BMDMs from female C57BL/6 mice expressed higher levels of interferon-gammaRalpha, and also produced more interleukin (IL)-12, IL-6 and NO than both the sham controls and E2-treated male-derived macrophages. Sham-treated BMDMs from female PI3Kgamma-/- C57BL/6 mice displayed lower infection rates and infection levels compared to sham-treated wild-type (WT) macrophages. However E2, unlike its effect on macrophages from female WT C57BL/6 mice, failed to reduce infection rates and infection levels in BMDMs from female PI3Kgamma-/- mice. Interestingly, E2-treated BMDMs from female C57BL/6 mice produced significant amounts of inflammatory cytokines and NO in levels comparable to those observed in sham-treated PI3Kgamma-deficient macrophages as well as E2-treated macrophages from WT mice. These findings show that E2 exerts a distinct effect on leishmanicidal activity of macrophages from male versus female C57BL/6 mice. In addition, they suggest that PI3Kgamma is not required for E2-induced cytokine and NO production in L. mexicana-infected macrophages from female C57BL/6 mice but it may be involved in parasite clearance from these cells.     

IL-12 is required for antibody-mediated protective immunity against blood-stage Plasmodium chabaudi AS malaria infection in mice.

In this study, we investigated the role of endogenous IL-12 in protective immunity against blood-stage P. chabaudi AS malaria using IL-12 p40 gene knockout (KO) and wild-type (WT) C57BL/6 mice. Following infection, KO mice developed significantly higher levels of primary parasitemia than WT mice and were unable to rapidly resolve primary infection and control challenge infection. Infected KO mice had severely impaired IFN-gamma production in vivo and in vitro by NK cells and splenocytes compared with WT mice. Production of TNF-alpha and IL-4 was not compromised in infected KO mice. KO mice produced significantly lower levels of Th1-dependent IgG2a and IgG3 but a higher level of Th2-dependent IgG1 than WT mice during primary and challenge infections. Treatment of KO mice with murine rIL-12 during the early stage of primary infection corrected the altered IgG2a, IgG3, and IgG1 responses and restored the ability to rapidly resolve primary and control challenge infections. Transfer of immune serum from WT mice to P. chabaudi AS-infected susceptible A/J mice completely protected the recipients, whereas immune serum from KO mice did not, as evidenced by high levels of parasitemia and 100% mortality in recipient mice. Furthermore, depletion of IgG2a from WT immune serum significantly reduced the protective effect of the serum while IgG1 depletion had no significant effect. Taken together, these results demonstrate the protective role of a Th1-immune response during both acute and chronic phases of blood-stage malaria and extend the immunoregulatory role of IL-12 to Ab-mediated immunity against Plasmodium parasites.     

Helicobacter pylori-induced mucosal inflammation is Th1 mediated and exacerbated in IL-4, but not IFN-gamma, gene-deficient mice

To elucidate the pathogenesis of Helicobacter pylori-associated gastritis, we studied immune responses of C57BL/6J wild-type (WT), SCID, and gene deficient (IFN-gamma-/- and IL-4-/-) mice following infection with a pathogenic isolate of H. pylori (SPM326). During early infection in WT mice, mononuclear and polymorphonuclear cells accumulated in the gastric lamina propria, and the numbers of cells in the inflamed mucosa expressing IFN-gamma, but not IL-4, mRNA rose significantly (p < 0.005), consistent with a local Th1 response. Splenic T cells from the same infected WT mice produced high levels of IFN-gamma, no detectable IL-4, and low amounts of IL-10 following in vitro H. pylori urease stimulation, reflecting a systemic Th1 response. Infected C57BL/6J SCID mice did not develop gastric inflammation despite colonization by many bacteria. Infected C57BL/10J and BALB/c mice also did not develop gastric inflammation and displayed a mixed Th1/Th2 splenic cytokine profile. These data imply a major role for the Th1 cytokine IFN-gamma in H. pylori-associated gastric inflammation in C57BL/6J mice. Compared with WT animals, infected IL-4-/- animals had more severe gastritis and higher levels of IFN-gamma production by urease-stimulated splenocytes (p < 0.01), whereas IFN-gamma-/- mice exhibited no gastric inflammation and higher levels of IL-4 production by stimulated splenocytes. These findings establish C57BL/6J mice as an important model for H. pylori infection and demonstrate that up-regulated production of IFN-gamma, in the absence of the opposing effects of IL-4 (and possibly IL-10), plays a pivotal role in promoting H. pylori-induced mucosal inflammation.     

Role of IL-6 in Exercise Training- and Cold-Induced UCP1 Expression in Subcutaneous White Adipose Tissue

Expression of brown adipose tissue (BAT) associated proteins like uncoupling protein 1 (UCP1) in inguinal WAT (iWAT) has been suggested to alter iWAT metabolism. The aim of this study was to investigate the role of interleukin-6 (IL-6) in exercise training and cold exposure-induced iWAT UCP1 expression. The effect of daily intraperitoneal injections of IL-6 (3 ng/g) in C57BL/6 mice for 7 days on iWAT UCP1 expression was examined. In addition, the expression of UCP1 in iWAT was determined in response to 3 days of cold exposure (4°C) and 5 weeks of exercise training in wild type (WT) and whole body IL-6 knockout (KO) mice. Repeated injections of IL-6 in C57BL/6 mice increased UCP1 mRNA but not UCP1 protein content in iWAT. Cold exposure increased iWAT UCP1 mRNA content similarly in IL-6 KO and WT mice, while exercise training increased iWAT UCP1 mRNA in WT mice but not in IL-6 KO mice. Additionally, a cold exposure-induced increase in iWAT UCP1 protein content was blunted in IL-6 KO mice, while UCP1 protein content in iWAT was lower in both untrained and exercise trained IL-6 KO mice than in WT mice. In conclusion, repeated daily increases in plasma IL-6 can increase iWAT UCP1 mRNA content and IL-6 is required for an exercise training-induced increase in iWAT UCP1 mRNA content. In addition IL-6 is required for a full induction of UCP1 protein expression in response to cold exposure and influences the UCP1 protein content iWAT of both untrained and exercise trained animals.     

Angiotensin II hypertension is attenuated in interleukin-6 knockout mice

Plasma levels of IL-6 correlate with high blood pressure under many circumstances, and ANG II has been shown to stimulate IL-6 production from various cell types. This study tested the role of IL-6 in mediating the hypertension caused by high-dose ANG II and a high-salt diet. Male C57BL6 and IL-6 knockout (IL-6 KO) mice were implanted with biotelemetry devices and placed in metabolic cages to measure mean arterial pressure (MAP), heart rate (HR), sodium balance, and urinary albumin excretion. Baseline MAP during the control period averaged 114 +/- 1 and 109 +/- 1 mmHg for wild-type (WT) and IL-6 KO mice, respectively, and did not change significantly when the mice were placed on a high-salt diet (HS; 4% NaCl). ANG II (90 ng/min sc) caused a rapid increase in MAP in both groups, to 141 +/- 9 and 141 +/- 4 in WT and KO mice, respectively, on day 2. MAP plateaued at this level in KO mice (134 +/- 2 mmHg on day 14 of ANG II) but began to increase further in WT mice by day 4, reaching an average of 160 +/- 4 mmHg from days 10 to 14 of ANG II. Urinary albumin excretion on day 4 of ANG II was not different between groups (9.18 +/- 4.34 and 8.53 +/- 2.85 microg/2 days for WT and KO mice). By day 14, albumin excretion was nearly fourfold greater in WT mice, but MAP dropped rapidly back to control levels in both groups when the ANG II was stopped after 14 days. Thus the approximately 30 mmHg greater ANG II hypertension in the WT mice suggests that IL-6 contributes significantly to ANG II-salt hypertension. In addition, the early separation in MAP, the albumin excretion data, and the rapid, post-ANG II recovery of MAP suggest an IL-6-dependent mechanism that is independent of renal injury.     

Role of IL-5 in innate and adaptive immunity to larval Strongyloides stercoralis in mice

Protective immunity to Strongyloides stercoralis infective larvae in mice has been shown to be dependent on IL-5 based on mAb depletion studies. The goal of this study was to determine the functional role of IL-5 during the innate and adaptive immune response to larval S. stercoralis in mice. In these studies, three strains of mice were used: wild-type C57BL/6J (WT), IL-5 knockout (KO), and IL-5 transgenic (TG). Innate responses to the larvae indicated that there was enhanced survival in the KO animals and decreased survival in the TG animals compared with WT. Furthermore, killing of larvae in TG mice was associated with eosinophil infiltration and degranulation. In studying the adaptive immune response, it was observed that immunization of KO mice did not lead to the development of protective immunity. Experiments were then performed to determine whether KO mice reconstituted with Abs or cells could then develop protective immunity. KO mice displayed protective immunity via a granulocyte-dependent mechanism following injection of purified IgM from immune wild-type animals. Immunity in KO mice could also be reconstituted by the injection of eosinophils at the time of immunization. These eosinophils did not participate in actively killing the challenge infection, but rather were responsible for the induction of a protective Ab response. We conclude that IL-5 is required in the protective immune response for the production of eosinophils, and that eosinophils were involved in larval killing during innate immunity and in the induction of protective Abs in the adaptive immune response.