Tpl2 Ablation Leads to Hypercytokinemia and Excessive Cellular Infiltration to the Lungs During Late Stages of Influenza Infection.

Tumor progression locus 2 (Tpl2) is a serine-threonine kinase known to promote inflammation in response to various pathogen-associated molecular patterns (PAMPs), inflammatory cytokines and G-protein-coupled receptors and consequently aids in host resistance to pathogens. We have recently shown that Tpl2-/- mice succumb to infection with a low-pathogenicity strain of influenza (x31, H3N2) by an unknown mechanism. In this study, we sought to characterize the cytokine and immune cell profile of influenza-infected Tpl2-/- mice to gain insight into its host protective effects. Although Tpl2-/- mice display modestly impaired viral control, no virus was observed in the lungs of Tpl2-/- mice on the day of peak morbidity and mortality suggesting that morbidity is not due to virus cytopathic effects but rather to an overactive antiviral immune response. Indeed, increased levels of interferon-ß (IFN-ß), the IFN-inducible monocyte chemoattractant protein-1 (MCP-1, CCL2), Macrophage inflammatory protein 1 alpha (MIP-1α; CCL3), MIP-1ß (CCL4), RANTES (CCL5), IP-10 (CXCL10) and Interferon-γ (IFN-γ) was observed in the lungs of influenza-infected Tpl2-/- mice at 7 days post infection (dpi). Elevated cytokine and chemokines were accompanied by increased infiltration of the lungs with inflammatory monocytes and neutrophils. Additionally, we noted that increased IFN-ß correlated with increased CCL2, CXCL1 and nitric oxide synthase (NOS2) expression in the lungs, which has been associated with severe influenza infections. Bone marrow chimeras with Tpl2 ablation localized to radioresistant cells confirmed that Tpl2 functions, at least in part, within radioresistant cells to limit pro-inflammatory response to viral infection. Collectively, this study suggests that Tpl2 tempers inflammation during influenza infection by constraining the production of interferons and chemokines which are known to promote the recruitment of detrimental inflammatory monocytes and neutrophils.

Tpl2 kinase regulates inflammation but not tumorigenesis in mice.

Tumor progression locus 2 (Tpl2, gene name MAP3K8), a mitogen-activated protein kinase, is widely expressed in immune and non-immune cells to integrate tumor necrosis factor (TNF), toll-like receptors (TLRs), and interleukin-1 (IL1) receptor signaling to regulate inflammatory response. Given its central role in inflammatory response, Tpl2 is an attractive small molecule drug target. However, the role of Tpl2 as an oncogene or tumor suppressor gene remains controversial, and its function outside immune cells is not understood. We therefore utilized a Tpl2 kinase dead (Tpl2-KD) mouse model in an 18-month aging study to further elucidate Tpl2 effects on lifespan and chronic disease. Histopathological studies revealed the incidence and severity of spontaneous tumors and non-neoplastic lesions were comparable between wild type and Tpl2-KD mice. The only finding was that male Tpl2-KD mice had higher bodyweight and an increased incidence of liver steatosis, suggesting a sex-specific role for Tpl2 in hepatic lipid metabolism. In conclusion, loss of Tpl2 kinase activity did not lead to increased tumorigenesis over aging in mice but affected likely alterations in lipid metabolism in male animals.

ABIN-2, of the TPL-2 Signaling Complex, Modulates Mammalian Inflammation.

Mammalian TPL-2 kinase (MAP3K8) mediates Toll-like receptor activation of ERK1/2 and p38α MAP kinases and is critical for regulating immune responses to pathogens. TPL-2 also has an important adaptor function, maintaining stability of associated ABIN-2 ubiquitin-binding protein. Consequently, phenotypes detected in Map3k8-/- mice can be caused by lack of TPL-2, ABIN-2, or both proteins. Recent studies show that increased inflammation of Map3k8-/- mice in allergic airway inflammation and colitis results from reduced ABIN-2 signaling, rather than blocked TPL-2 signaling. However, Map3k8-/- mice have been employed extensively to evaluate the potential of TPL-2 as an anti-inflammatory drug target. We posit that Map3k8D270A/D270A mice, expressing catalytically inactive TPL-2 and physiologic ABIN-2, should be used to evaluate the potential effects of TPL-2 inhibitors in disease.

MLK3 silence induces cervical cancer cell apoptosis via the Notch-1/autophagy network.

Mixed-lineage kinase 3 (MLK3), the mitogen-activated protein kinase kinase kinase (MAP3K), has been recognized as a player in tumorigenesis and oncogenic signalling, yet its detailed functions and signalling in cervical cancer have not been fully elucidated. Here, we identify that cervical cancer cells display higher mRNA and protein levels of MLK3 than normal cervical epithelial squamous cells. In HeLa and SiHa cell, MLK3 knockdown using siRNA remarkably suppressed cell survival and promoted cell apoptosis, with increased expression of the apoptosis-related protein Bax and reduced Bcl-2. Moreover, MLK3 knockdown promoted cell autophagy, demonstrated by increased ratio of autophagy-related proteins LC3II/LC3I and decreased p62 expression in MLK3 depletion cells. Furthermore, MLK3 knockdown remarkably abolished Notch-1 expression in cervical cancer cells. By co-treating Hela cells with MLK3 specific siRNA and pcDNA3.1-Notch-1 overexpression plasmid or autophagy inhibitor 3-MA, we found that MLK3 played its role in cervical cancer cells via the Notch-1/autophagy network. Our results demonstrate the importance of MLK3 in cervical cancer progression via modulating the Notch-1/autophagy network, and suggest that MLK3 is a promising therapeutic target for cervical cancer.

Coordinating Tissue Regeneration Through Transforming Growth Factor-ß Activated Kinase 1 Inactivation and Reactivation.

Aberrant wound healing presents as inappropriate or insufficient tissue formation. Using a model of musculoskeletal injury, we demonstrate that loss of transforming growth factor-ß activated kinase 1 (TAK1) signaling reduces inappropriate tissue formation (heterotopic ossification) through reduced cellular differentiation. Upon identifying increased proliferation with loss of TAK1 signaling, we considered a regenerative approach to address insufficient tissue production through coordinated inactivation of TAK1 to promote cellular proliferation, followed by reactivation to elicit differentiation and extracellular matrix production. Although the current regenerative medicine paradigm is centered on the effects of drug treatment ("drug on"), the impact of drug withdrawal ("drug off") implicit in these regimens is unknown. Because current TAK1 inhibitors are unable to phenocopy genetic Tak1 loss, we introduce the dual-inducible COmbinational Sequential Inversion ENgineering (COSIEN) mouse model. The COSIEN mouse model, which allows us to study the response to targeted drug treatment ("drug on") and subsequent withdrawal ("drug off") through genetic modification, was used here to inactivate and reactivate Tak1 with the purpose of augmenting tissue regeneration in a calvarial defect model. Our study reveals the importance of both the "drug on" (Cre-mediated inactivation) and "drug off" (Flp-mediated reactivation) states during regenerative therapy using a mouse model with broad utility to study targeted therapies for disease. Stem Cells 2019;37:766-778.

BMPRIA is required for osteogenic differentiation and RANKL expression in adult bone marrow mesenchymal stromal cells.

Bone morphogenetic proteins (BMPs) activate the canonical Smad1/5/8 and non-canonical Tak1-MAPK pathways via BMP receptors I and II to regulate skeletal development and bone remodeling. Specific ablation of Bmpr1a in immature osteoblasts, osteoblasts, or osteocytes results in an increase in cancellous bone mass, yet opposite results have been reported regarding the underlying mechanisms. Moreover, the role for BMPRIA-mediated signaling in bone marrow mesenchymal stromal cells (BM-MSCs) has not been explored. Here, we specifically ablated Bmpr1a in BM-MSCs in adult mice to study the function of BMPR1A in bone remodeling and found that the mutant mice showed an increase in cancellous and cortical bone mass, which was accompanied by a decrease in bone formation rate and a greater decrease in bone resorption. Decreased bone formation was associated with a defect in BM-MSC osteogenic differentiation whereas decreased bone resorption was associated with a decrease in RANKL production and osteoclastogenesis. However, ablation of Tak1, a critical non-canonical signaling molecule downstream of BMP receptors, in BM-MSCs at adult stage did not affect bone remodeling. These results suggest that BMP signaling through BMPRIA controls BM-MSC osteogenic differentiation/bone formation and RANKL expression/osteoclastogenesis in adult mice independent of Tak1 signaling.

TPL2 Is a Key Regulator of Intestinal Inflammation in Clostridium difficile Infection.

Tumor progression locus 2 (TPL2), a serine/threonine protein kinase, is a major inflammatory mediator in immune cells. The predominant inflammatory actions of TPL2 depend on the activation of mitogen-activated protein kinases (MAPK) and the upregulated production of the cytokines tumor necrosis factor alpha (TNF-α) and interleukin 1ß (IL-1ß) in macrophages and dendritic cells in response to lipopolysaccharide (LPS). Significant increases in TNF-α, IL-6, IL-ß, and IL-8 levels in patients with Clostridium difficile infection (CDI) have been reported. Both TNF-α and IL-6 have been postulated to play key roles in the systemic inflammatory response in CDI, and IL-8 is essential for the development of local intestinal inflammatory responses in CDI. The objective of this study was to elucidate the role of TPL2 in the pathogenesis of CDI. We found that TPL2 was significantly activated in human and mouse intestinal tissues upon C. difficile toxin exposure or CDI. We further demonstrated that TPL2 knockout (TPL2-KO) mice were significantly more resistant to CDI than wild-type mice, with significantly reduced production of TNF-α, IL-6, IL-1ß, KC (a mouse homologue of IL-8), and myeloperoxidase (MPO) in the ceca and colons of TPL2-KO mice. Finally, we found that TPL2 inhibition by a specific inhibitor or TPL2 gene ablation significantly reduced TcdB-induced production of TNF-α, IL-6, IL-ß, and KC by inhibiting the activation of p38, extracellular signal-regulated kinase (ERK), and c-Jun NH2-terminal kinase (JNK). Taken together, our data suggest that TPL2 represents a potential therapeutic target for CDI treatment.

The contribution of toll-like receptor signaling to the development of liver fibrosis and cancer in hepatocyte-specific TAK1-deleted mice.

Hepatocyte death is associated with liver inflammation, fibrosis and hepatocellular carcinoma (HCC). Damaged cells trigger inflammation through activation of Toll-like receptors (TLRs). Although the role of TLR4 in HCC development has been reported, the role of TLR9 in the development of HCC remains elusive. To investigate the role of TLR4 and TLR9 signaling in liver inflammation-fibrosis-cancer axis, we took advantage of mice with hepatic deletion of transforming growth factor-ß-activated kinase 1 (Tak1ΔHep) that develop spontaneous liver injury, inflammation, fibrosis, and HCC, recapitulating the pathology of human HCC. We generated double knockout mice lacking genes of our interest with hepatic Tak1. Tak1ΔHep mice and Tlr4-deficient Tak1ΔHep mice had similar serum ALT levels, but Tlr4-deficient Tak1ΔHep mice exhibited significantly reduced macrophage infiltration, myofibroblast activation and tumor formation. Ablation of TLR9 reduced spontaneous liver injury, inflammation, fibrosis, and cancer development in Tak1ΔHep mice. In addition, the common adaptor, myeloid differentiation factor 88 (MyD88)-deficient Tak1ΔHep mice also attenuated liver injury, macrophage recruitment, collagen deposition, and tumor growth compared with control Tak1ΔHep mice. Genetic ablation of TNF receptor type I (TNFR) in Tak1ΔHep mice remarkably reduced liver inflammation-fibrosis-cancer axis. Surprisingly, disruption of interleukin-1 receptor (IL-1R) had no effect on liver injury and tumor formation, although Il1r-deficient Tak1ΔHep showed attenuated macrophage infiltration and collagen deposition. In conclusion, TLR4- and TLR9-MyD88 are driving forces of progression to HCC accompanied by liver inflammation and fibrosis in Tak1ΔHep mice. Importantly, TLR4 and TLR9 downstream TNFR, but not IL-1R signaling is crucial for the development of HCC in Tak1ΔHep mice.

Tpl2 Promotes Innate Cell Recruitment and Effector T Cell Differentiation To Limit Citrobacter rodentium Burden and Dissemination.

Tumor progression locus 2 (Tpl2) is a serine-threonine kinase that regulates Th1 differentiation, secretion of the inflammatory cytokine gamma interferon (IFN-γ), and host defense against the intracellular pathogens Toxoplasma gondii, Listeria monocytogenes, and Mycobacterium tuberculosis However, relatively little is known about the contribution of Tpl2 to Th17 differentiation and immune cell function during infection with an extracellular pathogen. The goal of this study was to determine whether Tpl2 influences the immune response generated to the extracellular bacterium Citrobacter rodentium, which induces a mixed Th1 and Th17 response. During peak infection with C. rodentium, Tpl2-/- mice experienced greater bacterial burdens with evidence of dissemination to the liver and spleen but ultimately cleared the bacteria within 3 weeks postinfection, similar to the findings for wild-type mice. Tpl2-/- mice also recruited fewer neutrophils and monocytes to the colon during peak infection, which correlated with increased bacterial burdens. In mixed bone marrow chimeras, Tpl2 was shown to play a T cell-intrinsic role in promoting both IFN-γ and interleukin-17A production during infection with C. rodentium However, upon CD4 T cell transfer into Rag-/- mice, Tpl2-/- CD4 T cells were as protective as wild-type CD4 T cells against the dissemination of bacteria and mortality. These data indicate that the enhanced bacterial burdens in Tpl2-/- mice are not caused primarily by impairments in CD4 T cell function but result from defects in innate immune cell recruitment and function.

Severe Dermatitis Associated with Spontaneous Staphylococcus xylosus Infection in Rag-/-Tpl2-/- Mice.

Staphylococcus xylosus is a commensal bacterium found on the skin and mucosal surfaces of SPF mice. S. xylosus is rarely pathogenic, most often causing skin lesions and dermatitis in immunocompromised mice, particularly those with impaired NADPH oxidase function. Here we report spontaneous infection with S. xylosus in Rag1-/-Tpl2-/- mice. Infection was characterized by the presence of alopecia, crusts, and scaly skin. S. xylosus was detected in the feces, skin, lymph nodes, and lungs of Rag1-/-Tpl2-/- mice and led to mortality or euthanasia due to humane endpoints. C57BL/6 mice were culture-positive for S. xylosus on the skin, and Rag1-/- and Tpl2-/- mice were culture-positive on the skin and occasionally in the feces. However, S. xylosus did not cause clinical symptoms in C57BL/6, Rag1-/-, or Tpl2-/- mice. Compared with those in Rag1-/- mice, relative concentrations of circulating monocytes, but not neutrophils or lymphocytes, were increased in Rag1-/-Tpl2-/- mice, consistent with their increased incidence of clinical symptoms. Overall, this case study suggests a novel role for Tpl2 in T-cell-independent host resistance to the otherwise commensal organism S. xylosus.

Map3k8 Modulates Monocyte State and Atherogenesis in ApoE-/- Mice.

OBJECTIVE: Map3k8 (Cot/Tpl2) activates the MKK1/2-ERK1/2, MAPK pathway downstream from interleukin-1R, tumor necrosis factor-αR, NOD-2R (nucleotide-binding oligomerization domain-like 2R), adiponectinR, and Toll-like receptors. Map3k8 plays a key role in innate and adaptive immunity and influences inflammatory processes by modulating the functions of different cell types. However, its role in atherogenesis remains unknown. In this study, we analyzed the role of this kinase in this pathology. APPROACH AND RESULTS: We show here that Map3k8 deficiency results in smaller numbers of Ly6ChighCD11clow and Ly6ClowCD11chigh monocytes in ApoE-/- mice fed a high-fat diet (HFD). Map3k8-/-ApoE-/- monocytes displayed high rates of apoptosis and reduced amounts of Nr4a1, a transcription factor known to modulate apoptosis in Ly6ClowCD11chigh monocytes. Map3k8-/-ApoE-/- splenocytes and macrophages showed irregular patterns of cytokine and chemokine expression. Map3k8 deficiency altered cell adhesion and migration in vivo and decreased CCR2 expression, a determinant chemokine receptor for monocyte mobilization, on circulating Ly6ChighCD11clow monocytes. Map3k8-/-ApoE-/- mice fed an HFD showed decreased cellular infiltration in the atherosclerotic plaque, with low lipid content. Lesions had similar size after Map3k8+/+ApoE-/- bone marrow transplant into Map3k8-/-ApoE-/- and Map3k8+/+ApoE-/- mice fed an HFD, whereas smaller plaques were observed after the transplantation of bone marrow lacking both ApoE and Map3k8. CONCLUSIONS: Map3k8 decreases apoptosis of monocytes and enhances CCR2 expression on Ly6ChighCD11clow monocytes of ApoE-/- mice fed an HFD. These findings explain the smaller aortic lesions in ApoE-/- mice with Map3k8-/-ApoE-/- bone marrow cells fed an HFD, supporting further studies of Map3k8 as an antiatherosclerotic target.

Increased apoptosis and browning of TAK1-deficient adipocytes protects against obesity.

Obesity is an increasing health problem worldwide, and nonsurgical strategies to treat obesity have remained rather inefficient. We here show that acute loss of TGF-ß-activated kinase 1 (TAK1) in adipocytes results in an increased rate of apoptotic adipocyte death and increased numbers of M2 macrophages in white adipose tissue. Mice with adipocyte-specific TAK1 deficiency have reduced adipocyte numbers and are resistant to obesity induced by a high-fat diet or leptin deficiency. In addition, adipocyte-specific TAK1-deficient mice under a high-fat diet showed increased energy expenditure, which was accompanied by enhanced expression of the uncoupling protein UCP1. Interestingly, acute induction of adipocyte-specific TAK1 deficiency in mice already under a high-fat diet was able to stop further weight gain and improved glucose tolerance. Thus, loss of TAK1 in adipocytes reduces the total number of adipocytes, increases browning of white adipose tissue, and may be an attractive strategy to treat obesity, obesity-dependent diabetes, and other associated complications.

A Novel Zak Knockout Mouse with a Defective Ribotoxic Stress Response.

Ricin activates the proinflammatory ribotoxic stress response through the mitogen activated protein 3 kinase (MAP3K) ZAK, resulting in activation of mitogen activated protein kinases (MAPKs) p38 and JNK1/2. We had a novel zak-/- mouse generated to study the role of ZAK signaling in vivo during ricin intoxication. To characterize this murine strain, we intoxicated zak-/- and zak+/+ bone marrow-derived murine macrophages with ricin, measured p38 and JNK1/2 activation by Western blot, and measured zak, c-jun, and cxcl-1 expression by qRT-PCR. To determine whether zak-/- mice differed from wild-type mice in their in vivo response to ricin, we performed oral ricin intoxication experiments with zak+/+ and zak-/- mice, using blinded histopathology scoring of duodenal tissue sections to determine differences in tissue damage. Unlike macrophages derived from zak+/+ mice, those derived from the novel zak-/- strain fail to activate p38 and JNK1/2 and have decreased c-jun and cxcl-1 expression following ricin intoxication. Furthermore, compared with zak+/+ mice, zak-/- mice have decreased duodenal damage following in vivo ricin challenge. zak-/- mice demonstrate a distinct ribotoxic stress-associated phenotype in response to ricin and therefore provide a new animal model for in vivo studies of ZAK signaling.

Fibroblast Growth Factor 21 Mediates Glycemic Regulation by Hepatic JNK.

The cJun NH2-terminal kinase (JNK)-signaling pathway is implicated in metabolic syndrome, including dysregulated blood glucose concentration and insulin resistance. Fibroblast growth factor 21 (FGF21) is a target of the hepatic JNK-signaling pathway and may contribute to the regulation of glycemia. To test the role of FGF21, we established mice with selective ablation of the Fgf21 gene in hepatocytes. FGF21 deficiency in the liver caused marked loss of FGF21 protein circulating in the blood. Moreover, the protective effects of hepatic JNK deficiency to suppress metabolic syndrome in high-fat diet-fed mice were not observed in mice with hepatocyte-specific FGF21 deficiency, including reduced blood glucose concentration and reduced intolerance to glucose and insulin. Furthermore, we show that JNK contributes to the regulation of hepatic FGF21 expression during fasting/feeding cycles. These data demonstrate that the hepatokine FGF21 is a key mediator of JNK-regulated metabolic syndrome.

NF-κB1 p105 suppresses lung tumorigenesis through the Tpl2 kinase but independently of its NF-κB function.

Nuclear factor-κB (NF-κB) is generally believed to be pro-tumorigenic. Here we report a tumor-suppressive function for NF-κB1, the prototypical member of NF-κB. While NF-κB1 downregulation is associated with high lung cancer risk in humans and poor patient survival, NF-κB1-deficient mice are more vulnerable to lung tumorigenesis induced by the smoke carcinogen, urethane. Notably, the tumor-suppressive function of NF-κB1 is independent of its classical role as an NF-κB factor, but instead through stabilization of the Tpl2 kinase. NF-κB1-deficient tumors exhibit 'normal' NF-κB activity, but a decreased protein level of Tpl2. Reconstitution of Tpl2 or the NF-κB1 p105, but not p50 (the processed product of p105), inhibits the tumorigenicity of NF-κB1-deficient lung tumor cells. Remarkably, Tpl2-knockout mice resemble NF-κB1 knockouts in urethane-induced lung tumorigenesis. Mechanistic studies indicate that p105/Tpl2 signaling is required for suppressing urethane-induced lung damage and inflammation, and activating mutations of the K-Ras oncogene. These studies reveal an unexpected, NF-κB-independent but Tpl2-depenednt role of NF-κB1 in lung tumor suppression. These studies also reveal a previously unexplored role of p105/Tpl2 signaling in lung homeostasis.

Blockade of TGF-ß-activated kinase 1 prevents advanced glycation end products-induced inflammatory response in macrophages.

Advanced glycation end products (AGEs), inflammatory-activated macrophages are essential in the initiation and progression of diabetic nephropathy (DN). TGF-ß-activated kinase 1 (TAK1) plays a vital role in innate immune responses and inflammation. However, little information has been available about the effects of AGEs on the regulation of TAK1 expression and underlying mechanisms in AGEs-stimulated macrophage activation. We hypothesized TAK1 signal pathway in AGEs conditions could be a vital factor contributing to macrophage activation and inflammation. Thus, in the present study, we used bone marrow-derived macrophages (BMMs) to explore the functional role and potential mechanisms of TAK1 pathway under AGEs conditions. Results indicated that TAK1 played important roles in AGEs-induced mitogen-activated protein kinases (MAPKs) and nuclear factor kappa B protein (NF-κB) activation, which regulated the production of monocyte chemo-attractant protein-1 (MCP-1) and tumor necrosis factor-alpha (TNF-α) in AGEs-stimulated macrophages. The results also suggested that TAK1 inhibitor (5Z-7-oxozeaenol) could inhibit AGEs-induced macrophage activation to down-regulate inflammatory cytokine production via MAPKs and NF-κB pathways, indicating that 5Z-7-oxozeaenol might be an immunoregulatory agent against AGEs-stimulated inflammatory response in DN.

The Tpl2 Kinase Regulates the COX-2/Prostaglandin E2 Axis in Adipocytes in Inflammatory Conditions.

Bioactive lipid mediators such as prostaglandin E2 (PGE2) have emerged as potent regulator of obese adipocyte inflammation and functions. PGE2 is produced by cyclooxygenases (COXs) from arachidonic acid, but inflammatory signaling pathways controlling COX-2 expression and PGE2 production in adipocytes remain ill-defined. Here, we demonstrated that the MAP kinase kinase kinase tumor progression locus 2 (Tpl2) controls COX-2 expression and PGE2 secretion in adipocytes in response to different inflammatory mediators. We found that pharmacological- or small interfering RNA-mediated Tpl2 inhibition in 3T3-L1 adipocytes decreased by 50% COX-2 induction in response to IL-1ß, TNF-α, or a mix of the 2 cytokines. PGE2 secretion induced by the cytokine mix was also markedly blunted. At the molecular level, nuclear factor κB was required for Tpl2-induced COX-2 expression in response to IL-1ß but was inhibitory for the TNF-α or cytokine mix response. In a coculture between adipocytes and macrophages, COX-2 was mainly increased in adipocytes and pharmacological inhibition of Tpl2 or its silencing in adipocytes markedly reduced COX-2 expression and PGE2 secretion. Further, Tpl2 inhibition in adipocytes reduces by 60% COX-2 expression induced by a conditioned medium from lipopolysaccharide (LPS)-treated macrophages. Importantly, LPS was less efficient to induce COX-2 mRNA in adipose tissue explants of Tpl2 null mice compared with wild-type and Tpl2 null mice displayed low COX-2 mRNA induction in adipose tissue in response to LPS injection. Collectively, these data established that activation of Tpl2 by inflammatory stimuli in adipocytes and adipose tissue contributes to increase COX-2 expression and production of PGE2 that could participate in the modulation of adipose tissue inflammation during obesity.

Mouse models of liver cancer.

Hepatocellular carcinoma (HCC) is the sixth most common cancer worldwide, and the third leading cause of cancer mortality. The great majority of patients are not eligible for curative therapies, and therapeutic approaches for advanced disease show only limited efficacy. Difficulties to treat HCC are due to the heterogenous genetic alterations of HCC, profound alterations in the hepatic microenvironment, and incomplete understanding of HCC biology. Mouse models of HCC will be helpful to improve our understanding of HCC biology, the contributions of the specific pathways and genetic alterations to carcinogenesis. In addition, mouse models of HCC may contribute to elucidate the role of the tumor microenvironment, and serve as models for preclinical studies. As no single mouse model is appropriate to study all of the above, we discuss key features and limitations of commonly used models. Furthermore, we provide detailed protocols for select models, in which HCC is induced genetically, chemically or by transplantation of tumor cells.

Osteopetrosis in TAK1-deficient mice owing to defective NF-κB and NOTCH signaling.

The MAP kinase TGFß-activated kinase (TAK1) plays a crucial role in physiologic and pathologic cellular functions including cell survival, differentiation, apoptosis, inflammation, and oncogenesis. However, the entire repertoire of its mechanism of action has not been elucidated. Here, we found that ablation of Tak1 in myeloid cells causes osteopetrosis in mice as a result of defective osteoclastogenesis. Mechanistically, Tak1 deficiency correlated with increased NUMB-like (NUMBL) levels. Accordingly, forced expression of Numbl abrogated osteoclastogenesis whereas its deletion partially restored osteoclastogenesis and reversed the phenotype of Tak1 deficiency. Tak1 deletion also down-regulated Notch intracellular domain (NICD), but increased the levels of the transcription factor recombinant recognition sequence binding protein at Jκ site (RBPJ), consistent with NUMBL regulating notch signaling through degradation of NICD, a modulator of RBPJ. Accordingly, deletion of Rbpj partially corrected osteopetrosis in Tak1-deficient mice. Furthermore, expression of active IKK2 in RBPJ/TAK1-deficient cells significantly restored osteoclastogenesis, indicating that activation of NF-κB is essential for complete rescue of the pathway. Thus, we propose that TAK1 regulates osteoclastogenesis by integrating activation of NF-κB and derepression of NOTCH/RBPJ in myeloid cells through inhibition of NUMBL.