Transcriptional repression of NFKBIA triggers constitutive IKK- and proteasome-independent p65/RelA activation in senescence.

The IκB kinase (IKK)-NF-κB pathway is activated as part of the DNA damage response and controls both inflammation and resistance to apoptosis. How these distinct functions are achieved remained unknown. We demonstrate here that DNA double-strand breaks elicit two subsequent phases of NF-κB activation in vivo and in vitro, which are mechanistically and functionally distinct. RNA-sequencing reveals that the first-phase controls anti-apoptotic gene expression, while the second drives expression of senescence-associated secretory phenotype (SASP) genes. The rapidly activated first phase is driven by the ATM-PARP1-TRAF6-IKK cascade, which triggers proteasomal destruction of inhibitory IκBα, and is terminated through IκBα re-expression from the NFKBIA gene. The second phase, which is activated days later in senescent cells, is on the other hand independent of IKK and the proteasome. An altered phosphorylation status of NF-κB family member p65/RelA, in part mediated by GSK3ß, results in transcriptional silencing of NFKBIA and IKK-independent, constitutive activation of NF-κB in senescence. Collectively, our study reveals a novel physiological mechanism of NF-κB activation with important implications for genotoxic cancer treatment.

NF-κB determines Paneth versus goblet cell fate decision in the small intestine.

Although the role of the transcription factor NF-κB in intestinal inflammation and tumor formation has been investigated extensively, a physiological function of NF-κB in sustaining intestinal epithelial homeostasis beyond inflammation has not been demonstrated. Using NF-κB reporter mice, we detected strong NF-κB activity in Paneth cells, in '+4/+5' secretory progenitors and in scattered Lgr5+ crypt base columnar stem cells of small intestinal (SI) crypts. To examine NF-κB functions in SI epithelial self-renewal, mice or SI crypt organoids ('mini-guts') with ubiquitously suppressed NF-κB activity were used. We show that NF-κB activity is dispensable for maintaining SI epithelial proliferation, but is essential for ex vivo organoid growth. Furthermore, we demonstrate a dramatic reduction of Paneth cells in the absence of NF-κB activity, concomitant with a significant increase in goblet cells and immature intermediate cells. This indicates that NF-κB is required for proper Paneth versus goblet cell differentiation and for SI epithelial homeostasis, which occurs via regulation of Wnt signaling and Sox9 expression downstream of NF-κB. The current study thus presents evidence for an important role for NF-κB in intestinal epithelial self-renewal.

Deficiency in IκBα in the intestinal epithelium leads to spontaneous inflammation and mediates apoptosis in the gut.

The IκB kinase (IKK)-NF-κB signaling pathway plays a multifaceted role in inflammatory bowel disease (IBD): on the one hand, it protects from apoptosis; on the other, it activates transcription of numerous inflammatory cytokines and chemokines. Although several murine models of IBD rely on disruption of IKK-NF-κB signaling, these involve either knockouts of a single family member of NF-κB or of upstream kinases that are known to have additional, NF-κB-independent, functions. This has made the distinct contribution of NF-κB to homeostasis in intestinal epithelium cells difficult to assess. To examine the role of constitutive NF-κB activation in intestinal epithelial cells, we generated a mouse model with a tissue-specific knockout of the direct inhibitor of NF-κB, Nfkbia/IκBα. We demonstrate that constitutive activation of NF-κB in intestinal epithelial cells induces several hallmarks of IBD including increased apoptosis, mucosal inflammation in both the small intestine and the colon, crypt hyperplasia, and depletion of Paneth cells, concomitant with aberrant Wnt signaling. To determine which NF-κB-driven phenotypes are cell-intrinsic, and which are extrinsic and thus require the immune compartment, we established a long-term organoid culture. Constitutive NF-κB promoted stem-cell proliferation, mis-localization of Paneth cells, and sensitization of intestinal epithelial cells to apoptosis in a cell-intrinsic manner. Increased number of stem cells was accompanied by a net increase in Wnt activity in organoids. Because aberrant Wnt signaling is associated with increased risk of cancer in IBD patients and because NFKBIA has recently emerged as a risk locus for IBD, our findings have critical implications for the clinic. In a context of constitutive NF-κB, our findings imply that general anti-inflammatory or immunosuppressive therapies should be supplemented with direct targeting of NF-κB within the epithelial compartment in order to attenuate apoptosis, inflammation, and hyperproliferation. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

In contrast to Western diet, a plant-based, high-fat, low-sugar diet does not exacerbate retinal endothelial injury in streptozotocin-induced diabetes.

Controversy remains about how diet affects the vascular endothelial dysfunction associated with disordered insulin-glucose homeostasis. It is postulated that the type and level of certain macronutrients contribute to endothelial dysfunction in vascular diabetes complications. However, it is not well understood how specific macronutrients affect the molecular inflammatory response under conditions of hyperglycemia. Here, we examined retinal microvascular endothelial injury in streptozotocin (STZ)-diabetic rats fed a laboratory Western diet (WD). WD, characterized by its high content of saturated fat, cholesterol, and sugar, significantly increased retinal leukocyte accumulation and endothelial injury in the STZ-diabetic rats. Suppression of endothelial NF-κB signaling in the STZ model reduced the WD-induced increase in leukocyte accumulation. To isolate the effect of dietary fat, we generated high-fat diets with varying fatty acid balance and type. These diets contained moderate amounts of carbohydrates but no sugar. We found that neither high levels of saturated or unsaturated fats per se increased retinal leukocyte accumulation and endothelial injury in the STZ-diabetic rat model but that the combination of high levels of dietary cholesterol with specific saturated fatty acids that are abundant in WD exacerbated leukocyte accumulation and endothelial injury in the retinas of STZ-diabetic rats.-Barakat, A., Nakao, S., Zandi, S., Sun, D., Schmidt-Ullrich, R., Hayes, K. C., Hafezi-Moghadam, A. In contrast to Western diet, a plant-based, high-fat, low-sugar diet does not exacerbate retinal endothelial injury in streptozotocin-induced diabetes.

Overactivation of the NF-κB pathway impairs molar enamel formation.

OBJECTIVE: Hypohidrotic ectodermal dysplasia (HED) is a hereditary disorder characterized by abnormal structures and functions of the ectoderm-derived organs, including teeth. HED patients exhibit a variety of dental symptoms, such as hypodontia. Although disruption of the EDA/EDAR/EDARADD/NF-κB pathway is known to be responsible for HED, it remains unclear whether this pathway is involved in the process of enamel formation. EXPERIMENTAL SUBJECTS AND METHODS: To address this question, we examined the mice overexpressing Ikkß (an essential component required for the activation of NF-κB pathway) under the keratin 5 promoter (K5-Ikkß). RESULTS: Upregulation of the NF-κB pathway was confirmed in the ameloblasts of K5-Ikkß mice. Premature abrasion was observed in the molars of K5-Ikkß mice, which was accompanied by less mineralized enamel. However, no significant changes were observed in the enamel thickness and the pattern of enamel rods in K5-Ikkß mice. Klk4 expression was significantly upregulated in the ameloblasts of K5-Ikkß mice at the maturation stage, and the expression of its substrate, amelogenin, was remarkably reduced. This suggests that abnormal enamel observed in K5-Ikkß mice was likely due to the compromised degradation of enamel protein at the maturation stage. CONCLUSION: Therefore, we could conclude that the overactivation of the NF-κB pathway impairs the process of amelogenesis.

Canonical BMP signaling in tubular cells mediates recovery after acute kidney injury.

Bone morphogenetic protein (BMP) signaling has been shown to modulate the development of renal fibrosis in animal models of kidney injury, but the downstream mediators are incompletely understood. In wild-type mice, canonical BMP signaling mediated by SMAD1/5/8 transcription factors was constitutively active in healthy renal tubules, transiently down-regulated after ischemia reperfusion injury (IRI), and reactivated during successful tubular regeneration. We then induced IRI in mice with a tubular-specific BMP receptor 1A (BMPR1A) deletion. These mice failed to reactivate SMAD1/5/8 signaling in the post-ischemic phase and developed renal fibrosis after injury. Using unbiased genomic analyses, we identified three genes encoding inhibitor of DNA-binding (ID) proteins (Id1, Id2, and Id4) as key targets of BMPR1A-SMAD1/5/8 signaling. BMPR1A-deficient mice failed to re-induce these targets following IRI. Instead, BMPR1A-deficiency resulted in activation of pro-fibrotic signaling proteins that are normally repressed by ID proteins, namely, p38 mitogen-activated protein kinase and cell cycle inhibitor p27. These data indicate that the post-ischemic activation of canonical BMP signaling acts endogenously to repress pro-fibrotic signaling in tubular cells and may help to prevent the progression of acute kidney injury to chronic kidney disease.

Lhx2 is a direct NF-κB target gene that promotes primary hair follicle placode down-growth.

In the epidermis of mice lacking transcription factor nuclear factor-kappa B (NF-κB) activity, primary hair follicle (HF) pre-placode formation is initiated without progression to proper placodes. NF-κB modulates WNT and SHH signaling at early stages of HF development, but this does not fully account for the phenotypes observed upon NF-κB inhibition. To identify additional NF-κB target genes, we developed a novel method to isolate and transcriptionally profile primary HF placodes with active NF-κB signaling. In parallel, we compared gene expression at the same developmental stage in NF-κB-deficient embryos and controls. This uncovered novel NF-κB target genes with potential roles in priming HF placodes for down-growth. Importantly, we identify Lhx2 (encoding a LIM/homeobox transcription factor) as a direct NF-κB target gene, loss of which replicates a subset of phenotypes seen in NF-κB-deficient embryos. Lhx2 and Tgfb2 knockout embryos exhibit very similar abnormalities in HF development, including failure of the E-cadherin suppression required for follicle down-growth. We show that TGFß2 signaling is impaired in NF-κB-deficient and Lhx2 knockout embryos and that exogenous TGFß2 rescues the HF phenotypes in Lhx2 knockout skin explants, indicating that it operates downstream of LHX2. These findings identify a novel NF-κB/LHX2/TGFß2 signaling axis that is crucial for primary HF morphogenesis, which may also function more broadly in development and disease.

NF-κB Activation Protects Oligodendrocytes against Inflammation.

NF-κB is a key player in inflammatory diseases, including multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). However, the effects of NF-κB activation on oligodendrocytes in MS and EAE remain unknown. We generated a mouse model that expresses IκBαΔN, a super-suppressor of NF-κB, specifically in oligodendrocytes and demonstrated that IκBαΔN expression had no effect on oligodendrocytes under normal conditions (both sexes). Interestingly, we showed that oligodendrocyte-specific expression of IκBαΔN blocked NF-κB activation in oligodendrocytes and resulted in exacerbated oligodendrocyte death and hypomyelination in young, developing mice that express IFN-γ ectopically in the CNS (both sexes). We also showed that NF-κB inactivation in oligodendrocytes aggravated IFN-γ-induced remyelinating oligodendrocyte death and remyelination failure in the cuprizone model (male mice). Moreover, we found that NF-κB inactivation in oligodendrocytes increased the susceptibility of mice to EAE (female mice). These findings imply the cytoprotective effects of NF-κB activation on oligodendrocytes in MS and EAE.SIGNIFICANCE STATEMENT Multiple sclerosis (MS) is an inflammatory demyelinating disease of the CNS. NF-κB is a major player in inflammatory diseases that acts by regulating inflammation and cell viability. Data indicate that NF-κB activation in inflammatory cells facilitates the development of MS. However, to date, attempts to understand the role of NF-κB activation in oligodendrocytes in MS have been unsuccessful. Herein, we generated a mouse model that allows for inactivation of NF-κB specifically in oligodendrocytes and then used this model to determine the precise role of NF-κB activation in oligodendrocytes in models of MS. The results presented in this study represent the first demonstration that NF-κB activation acts cell autonomously to protect oligodendrocytes against inflammation in animal models of MS.

Ectodysplasin/NF-κB Promotes Mammary Cell Fate via Wnt/ß-catenin Pathway.

Mammary gland development commences during embryogenesis with the establishment of a species typical number of mammary primordia on each flank of the embryo. It is thought that mammary cell fate can only be induced along the mammary line, a narrow region of the ventro-lateral skin running from the axilla to the groin. Ectodysplasin (Eda) is a tumor necrosis factor family ligand that regulates morphogenesis of several ectodermal appendages. We have previously shown that transgenic overexpression of Eda (K14-Eda mice) induces formation of supernumerary mammary placodes along the mammary line. Here, we investigate in more detail the role of Eda and its downstream mediator transcription factor NF-κB in mammary cell fate specification. We report that K14-Eda mice harbor accessory mammary glands also in the neck region indicating wider epidermal cell plasticity that previously appreciated. We show that even though NF-κB is not required for formation of endogenous mammary placodes, it is indispensable for the ability of Eda to induce supernumerary placodes. A genome-wide profiling of Eda-induced genes in mammary buds identified several Wnt pathway components as potential transcriptional targets of Eda. Using an ex vivo culture system, we show that suppression of canonical Wnt signalling leads to a dose-dependent inhibition of supernumerary placodes in K14-Eda tissue explants.

Central immune tolerance depends on crosstalk between the classical and alternative NF-κB pathways in medullary thymic epithelial cells.

Medullary thymic epithelial cells (mTECs) contribute to self-tolerance by expressing and presenting peripheral tissue antigens for negative selection of autoreactive T cells and differentiation of natural regulatory T cells. The molecular control of mTEC development remains incompletely understood. We here demonstrate by TEC-specific gene manipulation in mice that the NF-κB transcription factor subunit RelB, which is activated by the alternative NF-κB pathway, regulates development of mature mTECs in a dose-dependent manner. Mice with conditional deletion of Relb lacked mature mTECs and developed spontaneous autoimmunity. In addition, the NF-κB subunits RelA and c-Rel, which are both activated by classical NF-κB signaling, were jointly required for mTEC differentiation by directly regulating the transcription of Relb. Our data reveal a crosstalk mechanism between classical and alternative NF-κB pathways that tightly controls the development of mature mTECs to ensure self-tolerance.

Tubular Epithelial NF-κB Activity Regulates Ischemic AKI.

NF-κB is a key regulator of innate and adaptive immunity and is implicated in the pathogenesis of AKI. The cell type-specific functions of NF-κB in the kidney are unknown; however, the pathway serves distinct functions in immune and tissue parenchymal cells. We analyzed tubular epithelial-specific NF-κB signaling in a mouse model of ischemia-reperfusion injury (IRI)-induced AKI. NF-κB reporter activity and nuclear localization of phosphorylated NF-κB subunit p65 analyses in mice revealed that IRI induced widespread NF-κB activation in renal tubular epithelia and in interstitial cells that peaked 2-3 days after injury. To genetically antagonize tubular epithelial NF-κB activity, we generated mice expressing the human NF-κB super-repressor IκBαΔN in renal proximal, distal, and collecting duct epithelial cells. Compared with control mice, these mice exhibited improved renal function, reduced tubular apoptosis, and attenuated neutrophil and macrophage infiltration after IRI-induced AKI. Furthermore, tubular NF-κB-dependent gene expression profiles revealed temporally distinct functional gene clusters for apoptosis, chemotaxis, and morphogenesis. Primary proximal tubular cells isolated from IκBαΔN-expressing mice and exposed to hypoxia-mimetic agent cobalt chloride exhibited less apoptosis and expressed lower levels of chemokines than cells from control mice did. Our results indicate that postischemic NF-κB activation in renal tubular epithelia aggravates tubular injury and exacerbates a maladaptive inflammatory response.

Regional regulation of Filiform tongue papillae development by Ikkα/Irf6.

BACKGROUND: Non-gustatory filiform papillae play critical roles in helping to grip food, drawing food to the esophagus, cleaning the mouth, and spreading saliva. The molecular mechanisms of filiform tongue papillae development however are not fully understood. RESULTS: We found Ikkα and Irf6 expression in developing tongue epithelium, and describe here specific tongue abnormalities in mice with mutation of these genes, indicating a role for Ikkα and Irf6 in filiform papillae development. Ikkα and Irf6 mutant tongues showed ectopic vertical epithelium at the midline, while lateral sides of mutant tongues adhered to the oral mucosa. Both the ectopic median vertical epithelium and adhered epithelium exhibited the presence of filiform tongue papillae, whereas epithelium between the median vertical epithelium and adhered tongue showed a loss of filiform tongue papillae. Timing of filiform papillae development was found to be slightly different between the midline and lateral regions of the wild-type tongue. CONCLUSIONS: Filiform papillae thus develop through distinct molecular mechanisms between the regions of tongue dorsum in the medio-lateral axis, with some filiform papillae developing under the control of Ikkα and Irf6. Developmental Dynamics 245:937-946, 2016. © 2016 Wiley Periodicals, Inc.

Ectodysplasin regulates hormone-independent mammary ductal morphogenesis via NF-κB.

Ductal growth of the mammary gland occurs in two distinct stages. The first round of branching morphogenesis occurs during embryogenesis, and the second round commences at the onset of puberty. Currently, relatively little is known about the genetic networks that control the initial phases of ductal expansion, which, unlike pubertal development, proceeds independent of hormonal input in female mice. Here we identify NF-κB downstream of the TNF-like ligand ectodysplasin (Eda) as a unique regulator of embryonic and prepubertal ductal morphogenesis. Loss of Eda, or inhibition of NF-κB, led to smaller ductal trees with fewer branches. On the other hand, overexpression of Eda caused a dramatic NF-κB-dependent phenotype in both female and male mice characterized by precocious and highly increased ductal growth and branching that correlated with enhanced cell proliferation. We have identified several putative transcriptional target genes of Eda/NF-κB, including PTHrP, Wnt10a, and Wnt10b, as well as Egf family ligands amphiregulin and epigen. We developed a mammary bud culture system that allowed us to manipulate mammary development ex vivo and found that recombinant PTHrP, Wnt3A, and Egf family ligands stimulate embryonic branching morphogenesis, suggesting that these pathways may cooperatively mediate the effects of Eda.

Ectodysplasin and Wnt pathways are required for salivary gland branching morphogenesis.

The developing submandibular salivary gland (SMG) is a well-studied model for tissue interactions and branching morphogenesis. Its development shares similar features with other ectodermal appendages such as hair and tooth. The ectodysplasin (Eda) pathway is essential for the formation and function of several ectodermal organs. Mutations in the signaling components of the Eda pathway lead to a human syndrome known as hypohidrotic ectodermal dysplasia (HED), which is characterized by missing and malformed teeth, sparse hair and reduced sweating. Individuals with HED suffer also from dry mouth because of reduced saliva flow. In order to understand the underlying mechanism, we analyzed salivary gland development in mouse models with altered Eda pathway activities. We have found that Eda regulates growth and branching of the SMG via transcription factor NF-κB in the epithelium, and that the hedgehog pathway is an important mediator of Eda/NF-κB. We also sought to determine whether a similar reciprocal interplay between the Eda and Wnt/ß-catenin pathways, which are known to operate in other skin appendages, functions in developing SMG. Surprisingly and unlike in developing hair follicles and teeth, canonical Wnt signaling activity did not colocalize with Edar/NF-κB in salivary gland epithelium. Instead, we observed high mesenchymal Wnt activity and show that ablation of mesenchymal Wnt signaling either in vitro or in vivo compromised branching morphogenesis. We also provide evidence suggesting that the effects of mesenchymal Wnt/ß-catenin signaling are mediated, at least in part, through regulation of Eda expression.

The role of Irf6 in tooth epithelial invagination.

Thickening and the subsequent invagination of the epithelium are an important initial step in ectodermal organ development. Ikkα has been shown to play a critical role in controlling epithelial growth, since Ikkα mutant mice show protrusions (evaginations) of incisor tooth, whisker and hair follicle epithelium rather than invagination. We show here that mutation of the Interferon regulatory factor (Irf) family, Irf6 also results in evagination of incisor epithelium. In common with Ikkα mutants, Irf6 mutant evagination occurs in a NF-κB-independent manner and shows the same molecular changes as those in Ikkα mutants. Irf6 thus also plays a critical role in regulating epithelial invagination. In addition, we also found that canonical Wnt signaling is upregulated in evaginated incisor epithelium of both Ikkα and Irf6 mutant embryos.

NF-κB signaling in tanycytes mediates inflammation-induced anorexia.

OBJECTIVES: Infections, cancer, and systemic inflammation elicit anorexia. Despite the medical significance of this phenomenon, the question of how peripheral inflammatory mediators affect the central regulation of food intake is incompletely understood. Therefore, we have investigated the sickness behavior induced by the prototypical inflammatory mediator IL-1ß. METHODS: IL-1ß was injected intravenously. To interfere with IL-1ß signaling, we deleted the essential modulator of NF-κB signaling (Nemo) in astrocytes and tanycytes. RESULTS: Systemic IL-1ß increased the activity of the transcription factor NF-κB in tanycytes of the mediobasal hypothalamus (MBH). By activating NF-κB signaling, IL-1ß induced the expression of cyclooxygenase-2 (Cox-2) and stimulated the release of the anorexigenic prostaglandin E2 (PGE2) from tanycytes. When we deleted Nemo in astrocytes and tanycytes, the IL-1ß-induced anorexia was alleviated whereas the fever response and lethargy response were unchanged. Similar results were obtained after the selective deletion of Nemo exclusively in tanycytes. CONCLUSIONS: Tanycytes form the brain barrier that mediates the anorexic effect of systemic inflammation in the hypothalamus.

Wnt/beta-catenin signaling directs multiple stages of tooth morphogenesis.

Wnt/beta-catenin signaling plays key roles in tooth development, but how this pathway intersects with the complex interplay of signaling factors regulating dental morphogenesis has been unclear. We demonstrate that Wnt/beta-catenin signaling is active at multiple stages of tooth development. Mutation of beta-catenin to a constitutively active form in oral epithelium causes formation of large, misshapen tooth buds and ectopic teeth, and expanded expression of signaling molecules important for tooth development. Conversely, expression of key morphogenetic regulators including Bmp4, Msx1, and Msx2 is downregulated in embryos expressing the secreted Wnt inhibitor Dkk1 which blocks signaling in epithelial and underlying mesenchymal cells. Similar phenotypes are observed in embryos lacking epithelial beta-catenin, demonstrating a requirement for Wnt signaling within the epithelium. Inducible Dkk1 expression after the bud stage causes formation of blunted molar cusps, downregulation of the enamel knot marker p21, and loss of restricted ectodin expression, revealing requirements for Wnt activity in maintaining secondary enamel knots. These data place Wnt/beta-catenin signaling upstream of key morphogenetic signaling pathways at multiple stages of tooth development and indicate that tight regulation of this pathway is essential both for patterning tooth development in the dental lamina, and for controlling the shape of individual teeth.

A dual role for Ikk alpha in tooth development.

IKK alpha is a component of the I kappa B kinase (IKK) complex that plays a key role in the activation of NF-kappa B. In Ikk alpha mutant mice and mice expressing a transdominant negative mutant of I kappa B alpha (cI kappa B alpha Delta N), molars have abnormal cusps, indicating that Ikk alpha is involved in cusp formation through the NF-kappa B pathway. However, Ikk alpha mutant incisors also have an earlier phenotype where epithelium evaginates outward into the developing oral cavity rather than invaginating into the underlying mesenchyme. A similar evagination of epithelium was also observed in whisker development, suggesting that Ikk alpha contributes to the direction of epithelial growth during the early stages of development in many ectodermal appendages. Since cI kappa B alpha Delta N mice have normal incisor epithelial invagination, Ikk alpha's role appears to be NF-kappa B independent. Changes in Notch1, Notch2, Wnt7b, and Shh expression found in incisor epithelium of Ikk alpha mutants suggest that this NF-kappa B-independent function is mediated by Notch/Wnt/Shh signaling pathways.

Proteasome-mediated degradation of IkappaBalpha and processing of p105 in Crohn disease and ulcerative colitis.

Enhanced NF-kappaB activity is involved in the pathology of both forms of inflammatory bowel disease (IBD), Crohn disease (CD) and ulcerative colitis (UC). Here we analyzed the mechanism of proteasome-mediated NF-kappaB activation in CD and UC. Our studies demonstrate that the subunit composition and the proteolytic function of proteasomes differ between UC and CD. High expression of the immunoproteasome subunits beta1i and beta2i is characteristic of the inflamed mucosa of CD. In line with this, we found enhanced processing of NF-kappaB precursor p105 and degradation of inhibitor of NF-kappaB, IkappaBalpha, by immunoproteasomes isolated from the mucosa of CD patients. In comparison with healthy controls and CD patients, UC patients exhibited an intermediate phenotype regarding the proteasome-mediated processing/degradation of NF-kappaB components. Finally, increased expression of the NF-kappaB family member c-Rel in the inflamed mucosa of CD patients suggests that p50/c-Rel is important for IFN-gamma-mediated induction of immunoproteasomes via IL-12-driven Th1 responses. These findings suggest that distinct proteasome subunits influence the intensity of NF-kappaB-mediated inflammation in IBD patients.

Vascular endothelial cell-specific NF-kappaB suppression attenuates hypertension-induced renal damage.

Nuclear factor kappa B (NF-kappaB) participates in hypertension-induced vascular and target-organ damage. We tested whether or not endothelial cell-specific NF-kappaB suppression would be ameliorative. We generated Cre/lox transgenic mice with endothelial cell-restricted NF-kappaB super-repressor IkappaBalphaDeltaN (Tie-1-DeltaN mice) overexpression. We confirmed cell-specific IkappaBalphaDeltaN expression and reduced NF-kappaB activity after TNF-alpha stimulation in primary endothelial cell culture. To induce hypertension with target-organ damage, we fed mice a high-salt diet and N(omega)-nitro-l-arginine-methyl-ester (L-NAME) and infused angiotensin (Ang) II. This treatment caused a 40-mm Hg blood pressure increase in both Tie-1-DeltaN and control mice. In contrast to control mice, Tie-1-DeltaN mice developed a milder renal injury, reduced inflammation, and less albuminuria. RT-PCR showed significantly reduced expression of the NF-kappaB targets VCAM-1 and ICAM-1, compared with control mice. Thus, the data demonstrate a causal link between endothelial NF-kappaB activation and hypertension-induced renal damage. We conclude that in vivo NF-kappaB suppression in endothelial cells stops a signaling cascade leading to reduced hypertension-induced renal damage despite high blood pressure.