TWEAK/Fn14 Activation Participates in Skin Inflammation

TWEAK increases angiogenesis to promote diabetic skin wound healing by regulating Fn14/EGFR signaling

OBJECTIVE

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK), a member of tumor necrosis factor superfamily, can bind to fibroblast growth factor-inducible 14 (Fn14) receptor and stimulate angiogenesis. The interaction between epidermal growth factor receptor (EGFR) and endothelial growth factor (EGF) leads to EGFR signal transduction and promotes angiogenesis. The objective of this study was to explore whether TWEAK participated in the diabetic skin wound healing by regulating Fn14/EGFR signaling.

METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with 35 mmol/L d-glucose and classified into the Control Group, High Glucose (HG) Group and HG + TWEAK Group. Then, the TWEAK expression and the proliferation, migration and tubule formation of HUVECs were detected, respectively. In vivo experiment, the diabetic model was established by injecting streptozotocin (STZ, 50 mg/kg) into male BALB/c mice. On the back of successfully modeled diabetic mice, a full-thickness skin wound of 6 mm diameter was formed. Then, the mice were randomly assigned into three groups: Blank Group, Phosphate Buffer Saline (PBS) Group, and TWEAK Group. Subsequently, expression levels of TWEAK, Fn14, EGFR and vascular endothelial growth factor (VEGF)-A were measured, and the CD31 expression in the wounded skin tissue of mice was checked by immunohistochemistry staining.

RESULTS

The expression level of TWEAK in HUVECs of HG Group decreased significantly, as well as the viability, migration, and tubule formation of cells. After over-expression of TWEAK, the cell viability, migration, and tubule formation abilities of HUVECs recovered remarkably. In vivo, the wound healing rate of diabetic mice was raised, the neovascularization was increased, and the CD31 expression in the wounded tissue was obviously upregulated after injection with recombinant TWEAK antibody.

CONCLUSION

TWEAK stimulates angiogenesis and accelerates the wound healing of diabetic skin by regulating Fn14/EGFR signaling.

TWEAK/Fn14 disrupts Th17/Treg balance and aggravates conjunctivitis by inhibiting the Nrf2/HO-1 pathway in allergic conjunctivitis mice

BACKGROUND

Allergic conjunctivitis (AC) affects people's daily life and work, especially the health of children. Although there are few relevant studies, Th17/Treg imbalance plays an important role in AC development. The aim of this study was to elucidate the effect of TWEAK/Fn14 on AC and Th17/Treg balance.

METHODS

Ovalbumin induced AC mouse model was utilized to observe the mechanism of TWEAK/Fn14 in vivo. Conjunctivitis was evaluated by hematoxylin-eosin staining, toluidine blue staining and AC clinical score. Flow cytometry was used to measure Th17 and Treg cell ratios. The level of Th17/Treg balance related factors and Nrf2/HO-1 signal was detected by ELISA, WB, qRT-PCR and immunohistochemistry.

RESULTS

In the AC state, disruption of Th17/Treg cell balance, increased TWEAK/Fn14 signaling level and conjunctival inflammation were observed. After TWEAK knockdown, Th17 cell differentiation was inhibited, Treg cell differentiation was promoted, and AC symptoms were alleviated in AC mice. Moreover, TWEAK knockdown caused an enhancement of the Nrf2/HO-1 signaling pathway in the AC models. Treatment with Nrf2 inhibitor reversed these changes induced by TWEAK knockdown. Therefore, TWEAK/Fn14 regulated the Nrf2/HO-1 pathway to affect Th17/Treg cell balance and conjunctivitis in AC mouse models.

CONCLUSION

In summary, TWEAK/Fn14 caused Th17/Treg imbalance by inhibiting Nrf2/HO-1 pathway, which might be one potential mechanism of the exacerbation of AC.

Deciphering the Etiologies of Adult Erythroderma: An Updated Guide to Presentations, Diagnostic Tools, Pathophysiologies, and Treatments

Erythroderma, an inflammatory skin condition characterized by widespread erythema with variable degrees of exfoliation, pustulation, or vesiculobullous formation, is associated with high morbidity and mortality. Determining the underlying cause of erythroderma frequently presents a diagnostic challenge, which may contribute to the condition's relatively poor prognosis. This review covers the clinical presentation, pathophysiology, diagnosis, and treatment of erythroderma. It discusses similarities and differences among the many underlying etiologies of the condition and differences between erythrodermic and non-erythrodermic presentations of the same dermatosis. Finally, this article explores current research that may provide future tools in the diagnosis and management of erythroderma.

Anti-inflammatory Capacity of a Medicinal herb extract, Anemarrhena asphodeloides, on In vivo and In vitro models-induced atopic dermatitis

Anemarrhena asphodeloides (AA) Bunge, a rhizomatous plant from the Liliaceae family, is traditionally utilized to manage inflammatory conditions. Nevertheless, its impact on atopic dermatitis (AD) and the associated molecular pathways have not yet been fully explored. This study explored the therapeutic effects of AA on AD both in vivo, using 2,4-dinitrofluorobenzene-induced NC/Nga mice, and in vitro, with tumor necrosis factor-α/interferon-γ-stimulated HaCaT keratinocytes. Topical application of AA ointment on the dorsal skin notably alleviated AD symptoms and skin lesions, enhanced the dermatitis score, and improved parameters such as the rate of trans-epidermal water loss, epidermal thickness, mast cell infiltration, systemic IgE levels, and cytokine expression. Furthermore, AA treatment significantly reduced serum levels of thymic stromal lymphopoietin (TSLP) and locally suppressed mRNA expression of thymus and activation-regulated chemokine (TARC) along with other relevant cytokines in affected skin. Both in vivo and in vitro applications of AA curtailed TSLP levels by inhibiting the expression of signal transducer and activator of transcription 6, a key regulator of pruritus and an initiator of mitogen-activated protein kinase signaling pathways. Additionally, AA affected the expression of tumor necrosis factor-like weak inducer of apoptosis/fibroblast growth factor-inducible 14, a pathway of interest in the study of cutaneous inflammatory diseases. Collectively, these findings propose that AA holds potential as an effective therapeutic agent for treating AD-induced skin inflammation.

TWEAK levels in psoriatic patients treated with narrowband ultraviolet B and methotrexate

BACKGROUND

Psoriasis is an autoimmune disease which has an effect on the joints and skin. Tumor Necrosis Factor-Like Weak Inducer of Apoptosis (TWEAK) is a multi-functional cytokine which regulates the cellular processes and has been related to a variation of conditions.

OBJECTIVES

To measure the level of serum TWEAK in psoriatic diseased persons and its relationship to the PASI score pre- and post-therapy with narrowband ultraviolet B phototherapy (NB-UVB) and methotrexate (MTX).

METHODS

This randomized controlled trial was conducted on 40 patients and 20 healthy persons as controls. Patient Group was randomly subdivided to two groups. The 1st group consisted of 20 patients who received NB-UVB treatment. The 2nd group included 20 MTX-treated candidates. Blood samples were drawn from patients in order to detect serum TWEAK levels using ELISA. The research was registered on Clinical Trials Registration: RCT approval numbers: NCT0481191.

RESULTS

The mean PASI score percent improvement after 12 weeks of treatment was higher in the MTX group (90%) than NB-UVB group (60%). The serum TWEAK level at baseline was 60.47 ± 12.6 pg/mL in NB-UVB group and 54.69 ± 21.7 pg/mL in MTX group which reduced to 24.93 ± 17.6 pg/mL and 32.13 ± 23.6 pg/mL, respectively (p < 0.001), after 12 weeks of treatment. There was a positive correlation between the serum levels of TWEAK and severity of PASI score (r = 0.399, p = 0.014).

CONCLUSION

TWEAK grades in psoriasis are substantially higher than in controls. TWEAK levels were dramatically reduced during NB-UVB and MTX treatment. TWEAK may have a potential sign for psoriasis diagnosis and prognosis.

The cytokine receptor Fn14 is a molecular brake on neuronal activity that mediates circadian function in vivo

To survive, organisms must adapt to a staggering diversity of environmental signals, ranging from sensory information to pathogenic infection, across the lifespan. At the same time, organisms intrinsically generate biological oscillations, such as circadian rhythms, without input from the environment. While the nervous system is well-suited to integrate extrinsic and intrinsic cues, how the brain balances these influences to shape biological function system-wide is not well understood at the molecular level. Here, we demonstrate that the cytokine receptor Fn14, previously identified as a mediator of sensory experience-dependent synaptic refinement during brain development, regulates neuronal activity and function in adult mice in a time-of-day-dependent manner. We show that a subset of excitatory pyramidal (PYR) neurons in the CA1 subregion of the hippocampus increase Fn14 expression when neuronal activity is heightened. Once expressed, Fn14 constrains the activity of these same PYR neurons, suggesting that Fn14 operates as a molecular brake on neuronal activity. Strikingly, differences in PYR neuron activity between mice lacking or expressing Fn14 were most robust at daily transitions between light and dark, and genetic ablation of Fn14 caused aberrations in circadian rhythms, sleep-wake states, and sensory-cued and spatial memory. At the cellular level, microglia contacted fewer, but larger, excitatory synapses in CA1 in the absence of Fn14, suggesting that these brain-resident immune cells may dampen neuronal activity by modifying synaptic inputs onto PYR neurons. Finally, mice lacking Fn14 exhibited heightened susceptibility to chemically induced seizures, implicating Fn14 in disorders characterized by hyperexcitation, such as epilepsy. Altogether, these findings reveal that cytokine receptors that mediates inflammation in the periphery, such as Fn14, can also play major roles in healthy neurological function in the adult brain downstream of both extrinsic and intrinsic cues.

TWEAK and Fn14 are overexpressed in immune-mediated necrotizing myopathy: implications for muscle damage and repair

OBJECTIVES

TNF-like weak inducer of apoptosis (TWEAK) and its sole receptor fibroblast growth factor-inducible 14 (Fn14) are involved in various inflammatory conditions. This study was performed to investigate the potential role of TWEAK/Fn14 in immune-mediated necrotizing myopathy (IMNM).

METHODS

Muscle biopsies from patients with IMNM (n = 37) and controls (n = 11) were collected. Human muscle cells were treated with TWEAK in vitro. Muscle biopsies and cultured muscle cells were analysed by immunostaining and quantitative PCR. Serum levels of TWEAK and Fn14 were detected by ELISA.

RESULTS

TWEAK and Fn14 were overexpressed in IMNM muscle biopsies. The percentage of Fn14-positive myofibers correlated with disease severity, myonecrosis, regeneration and inflammation infiltrates. Fn14-positive myofibers tended to be surrounded or invaded by CD68+ macrophages. TWEAK treatment had a harmful effect on cultured muscle cells by inducing the production of multiple chemokines and pro-inflammatory cytokines. Serum Fn14 levels were increased in patients with IMNM and correlated with muscle weakness.

CONCLUSIONS

TWEAK/Fn14 signalling was activated in IMNM, most likely aggravating muscle damage via amplifying inflammatory response and macrophages chemotaxis. Fn14 seems to be a biomarker for assessing disease severity in IMNM. In addition, Fn14 may also contribute to muscle injury repair.

Artemisinin-Type Drugs in Tumor Cell Death: Mechanisms, Combination Treatment with Biologics and Nanoparticle Delivery

Artemisinin, the most famous anti-malaria drug initially extracted from Artemisia annua L., also exhibits anti-tumor properties in vivo and in vitro. To improve its solubility and bioavailability, multiple derivatives have been synthesized. However, to reveal the anti-tumor mechanism and improve the efficacy of these artemisinin-type drugs, studies have been conducted in recent years. In this review, we first provide an overview of the effect of artemisinin-type drugs on the regulated cell death pathways, which may uncover novel therapeutic approaches. Then, to overcome the shortcomings of artemisinin-type drugs, we summarize the recent advances in two different therapeutic approaches, namely the combination therapy with biologics influencing regulated cell death, and the use of nanocarriers as drug delivery systems. For the former approach, we discuss the superiority of combination treatments compared to monotherapy in tumor cells based on their effects on regulated cell death. For the latter approach, we give a systematic overview of nanocarrier design principles used to deliver artemisinin-type drugs, including inorganic-based nanoparticles, liposomes, micelles, polymer-based nanoparticles, carbon-based nanoparticles, nanostructured lipid carriers and niosomes. Both approaches have yielded promising findings in vitro and in vivo, providing a strong scientific basis for further study and upcoming clinical trials.

Anti-Inflammatory Effects of Lagerstroemia ovalifolia Teijsm. & Binn. in TNFα/IFNγ-Stimulated Keratinocytes

Ethnopharmacological Relevance. Atopic dermatitis is a chronic inflammatory skin disease. Lagerstroemia ovalifolia Teijsm. & Binn. (LO) has traditionally been used as an herbal medicine for anti-inflammatory diseases. The effect of LO on atopic dermatitis has not been verified scientifically. We investigated the effects of CHCl₃ fraction number 5 of LO (LOC) on atopic dermatitis through cell-based experiments. HaCaT cells were treated with tumor necrosis factor-alpha (TNFα)/interferon-gamma (IFNγ) to induce an inflammatory reaction. Proinflammatory cytokines, interleukin- (IL-) 6, IL-8, and IL-1β and chemokines such as thymus and activation-regulated chemokine (TARC/CCL17), monocyte chemoattractant protein 1 (MCP1/CCL2), and macrophage-derived chemokine (MDC/CCL22) were measured by RT-PCR and ELISA. In addition, the degree of phosphorylation and activation of JAK/STAT1, PI3K/AKT, and nuclear factor-kappa B (NF-κB) were measured by western blot and luciferase assays. The production of inflammatory cytokines and chemokines and activation of the JAK/STAT1, PI3K/AKT, and NF-κB pathways were induced by TNFα/IFNγ in HaCaT cells. Under these conditions, LOC treatment inhibited the production of targeted cytokines and chemokines and decreased the phosphorylation and activation of JAK/STAT1, PI3K/AKT, and NF-κB. These results suggest that LOC reduces the production of proinflammatory cytokines and chemokines by suppressing the JAK/STAT1, PI3K/AKT, and NF-κB pathways. Therefore, LOC may have potential as a drug for atopic dermatitis.

Diversity of cell death signaling pathways in macrophages upon infection with modified vaccinia virus Ankara (MVA)

Regulated cell death frequently occurs upon infection by intracellular pathogens, and extent and regulation is often cell-type-specific. We aimed to identify the cell death-signaling pathways triggered in macrophages by infection with modified vaccinia virus Ankara (MVA), an attenuated strain of vaccinia virus used in vaccination. While most target cells seem to be protected by antiapoptotic proteins encoded in the MVA genome, macrophages die when infected with MVA. We targeted key signaling components of specific cell death-pathways and pattern recognition-pathways using genome editing and small molecule inhibitors in an in vitro murine macrophage differentiation model. Upon infection with MVA, we observed activation of mitochondrial and death-receptor-induced apoptosis-pathways as well as the necroptosis-pathway. Inhibition of individual pathways had a little protective effect but led to compensatory death through the other pathways. In the absence of mitochondrial apoptosis, autocrine/paracrine TNF-mediated apoptosis and, in the absence of caspase-activity, necroptosis occurred. TNF-induction depended on the signaling molecule STING, and MAVS and ZBP1 contributed to MVA-induced apoptosis. The mode of cell death had a substantial impact on the cytokine response of infected cells, indicating that the immunogenicity of a virus may depend not only on its PAMPs but also on its ability to modulate individual modalities of cell death. These findings provide insights into the diversity of cell death-pathways that an infection can trigger in professional immune cells and advance our understanding of the intracellular mechanisms that govern the immune response to a virus.

Regenerative Effects of Hypoxia Primed Flowable Placental Formulation in Muscle and Dermal Injury

The placental tissue, due to its angiogenic, anti-inflammatory, antioxidative, antimicrobial, and anti-fibrotic properties, has become a compelling source towards a solution for several indications in regenerative medicine. However, methods to enhance and capture the therapeutic properties with formulations that can further the applications of viable placental tissue have not been explored. In this study, we investigated the regenerative effects of a hypoxia primed flowable placental formulation (FPF), composed of amnion/chorion and umbilical tissue, in two in vivo injury models. Laser Doppler data from rodent ischemia hindlimbs treated with FPF revealed significant tissue perfusion improvements compared to control ischemic hindlimbs. To further corroborate FPF's effects, we used a rodent ischemic bipedicle skin flap wound model. FPF treatment significantly increased the rate of wound closure and the quality of wound healing. FPF-treated wounds displayed reduced inflammation and an increase in angiogenesis. Furthermore, quantitative PCR and next-generation sequencing analysis confirmed these changes in the FPF-treated group at both the gene and transcriptional level. The observed modulation in miRNAs was associated with angiogenesis, regulation of inflammatory microenvironment, cell migration and apoptosis, reactive oxygen species generation, and restoring epithelial barrier function, all processes involved in impaired tissue healing. Taken together, these data validate the tissue regenerative properties of the flowable placental formulation configuration tested.

Adjunctive S100A8/A9 Immunomodulation Hinders Ciprofloxacin Resistance in Pseudomonas aeruginosa in a Murine Biofilm Wound Model

Objective

Pseudomonas aeruginosa is known to contribute to the pathogenesis of chronic wounds by biofilm-establishment with increased tolerance to host response and antibiotics. The neutrophil-factor S100A8/A9 has a promising adjuvant effect when combined with ciprofloxacin, measured by quantitative bacteriology, and increased anti- and lowered pro-inflammatory proteins. We speculated whether a S100A8/A9 supplement could prevent ciprofloxacin resistance in infected wounds.

Method

Full-thickness 2.9cm²-necrosis was inflicted on 32 mice. On day 4, P.aeruginosa in seaweed alginate was injected sub-eschar to mimic a mono-pathogenic biofilm. Mice were randomized to receive ciprofloxacin and S100A8/A9 (n=14), ciprofloxacin (n=12) or saline (n=6). Half of the mice in each group were euthanized day 6 and the remaining day 10 post-infection. Mice were treated until sacrifice. Primary endpoint was the appearance of ciprofloxacin resistant P.aeruginosa. The study was further evaluated by genetic characterization of resistance, means of quantitative bacteriology, wound-size and cytokine-production.

Results

Three mice receiving ciprofloxacin monotherapy developed resistance after 14 days. None of the mice receiving combination therapy changed resistance pattern. Sequencing of fluoroquinolone-resistance determining regions in the ciprofloxacin resistant isolates identified two high-resistant strains mutated in gyrA C248T (MIC>32µg/ml) and a gyr B mutation was found in the sample with low level resistance (MIC=3µg/ml). Bacterial densities in wounds were lower in the dual treated group compared to the placebo group on both termination days.

Conclusion

This study supports the ciprofloxacin augmenting effect and indicates a protective effect in terms of hindered ciprofloxacin resistance of adjuvant S100A8/A9 in P.aeruginosa biofilm infected chronic wounds.

Histology-based profile of inflammatory mediators in experimentally induced pulpitis in a rat model: screening for possible biomarkers

Aim

To profile molecular changes in lipopolysaccharide (LPS)‐induced experimental pulpitis in a rat model and explore the feasibility of a molecular‐based diagnostic strategy for pulpitis.

Methodology

Seventy‐three maxillary incisors of Sprague‐Dawley rats were used to establish pulpitis models with LPS. Inflammatory grading was performed in four equal sections of the pulp divided from the injured site to the root apex. An antibody array was used to compare the expression of 67 molecules between control pulp and inflamed pulp 12 and 72 h after LPS application. The levels of differentially expressed molecules in the control and inflamed pulp (collected at 3, 6, 9, 12, 24 and 72 h after LPS treatment) were examined via ELISA, and correlations between inflammatory scores and molecule expression were assessed. The molecule distributions in the pulp were investigated by immunofluorescence staining. Data were analysed with paired t‐test, one‐way anova, Kruskal–Wallis tests, and Spearman’s and Pearson’s correlations with significance set at P < 0.05.

Results

Polymorphonuclear neutrophils were observed in the injured site 3 h after LPS stimulation. Inflammatory infiltration peaked at 12 h and was limited to the injured site with osteodentine deposition at 72 h. Thirteen molecules were significantly differentially expressed between the control and LPS‐injured pulp. ELISA validated that tissue inhibitor of metalloproteinase‐1 (TIMP‐1) expression dramatically peaked at 12 h (compared with other time points, P < 0.05) and returned to baseline at 72 h. The TIMP‐1 concentration was strongly correlated with inflammation severity in the apical three‐quarters of the pulp, and the strongest correlation was found in the lower‐middle quarter (r = 0.786, P < 0.001). Immunofluorescence staining revealed that in the apical three‐quarters of the pulp, TIMP‐1 expression was significantly higher in the 12 h group than in the control and 3, 6, 24 and 72 h groups (P < 0.01).

Conclusion

This study provides a molecular profile of LPS‐induced pulpitis in a rat model. TIMP‐1 had a strong positive correlation with the severity of dental pulp inflammation, verifying the feasibility of applying biomarkers to identify specific pathological conditions in pulpitis.

Involvement of the cytokine TWEAK in the pathogenesis of psoriasis vulgaris, pustular psoriasis, and erythrodermic psoriasis

Psoriasis is a common chronic inflammatory dermatitis in which various cytokines play a detrimental role. The cytokine tumor necrosis factor-related weak inducer of apoptosis (TWEAK) is involved in the pathogenesis of multiple inflammatory disorders. However, the potential role of TWEAK in various subtypes of psoriasis has not been studied in depth. To investigate whether the levels of TWEAK are associated with clinical traits and the levels of some known psoriasis-related cytokines, such as interleukin (IL)-17A, IL-22, interferon (IFN)-γ, and IL-36γ, 20 patients with psoriasis vulgaris (PV), 8 patients with pustular psoriasis (PP), 8 patients with erythrodermic psoriasis (EP), and 20 healthy controls (HCs) were recruited into this study. The levels of serum cytokines were detected by commercial enzyme-linked immunosorbent assay kits. The average levels of TWEAK, IL-17A, IL-22, IFN-γ, and IL-36γ were significantly higher in the psoriasis groups than in the HC group. Furthermore, there was a statistically significant correlation between TWEAK and IL-17A/IFN-γ in PV and IL-36γ in EP, but there was no correlation between TWEAK and IL-22 in any subtype of psoriasis. This study suggests that TWEAK may have a role in the pathogenesis of PV, PP, and EP via synergy with IL-17A, IFN-γ, or IL-36γ, but not with IL-22.

Serum TWEAK: A cutoff between segmental and nonsegmental vitiligo

BACKGROUND

TWEAK/Fn14 is expressed in many tissues including the skin, playing an important role in many inflammatory, autoimmune, and neoplastic cutaneous disorders.

AIMS

To assess the serum levels of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) in vitiligo patients.

METHODS

This case-control study included 100 subjects (50 vitiligo patients and 50 control subjects) recruited from Dermatology Outpatient Clinic, Benha University. All patients were subjected to complete cutaneous examination, to evaluate the clinical type, distribution and severity of vitiligo using the Vitiligo Area Scoring Index (VASI).

RESULTS

TWEAK serum levels were significantly higher in patients than in the control subjects (644.76 ± 688.93 vs 282.75 ± 125.67, respectively). Serum levels were significantly elevated in segmental versus nonsegmental vitiligo. Receiver operating characteristic (ROC) analysis revealed that TWEAK shows 80% sensitivity and 56.67% specificity in diagnosing vitiligo and 100% sensitivity and 80.09% specificity in differentiating segmental from nonsegmental vitiligo.

CONCLUSION

TWEAK may play a role in vitiligo pathogenesis. It may be used in the differentiation between segmental and nonsegmental vitiligo and represent a promising therapeutic target in vitiligo.

Tumor Necrosis Factor-Like Weak Inducer of Apoptosis (TWEAK) Enhances Activation of STAT3/NLRC4 Inflammasome Signaling Axis through PKCδ in Astrocytes: Implications for Parkinson's Disease

Astrocytic dysfunction has been implicated in Parkinson's disease (PD) pathogenesis. While the Tumor necrosis factor-like weak inducer of apoptosis (TWEAK)/Fn14 signaling axis is known to play a role in PD-like neuropathology, the molecular mechanisms that govern this process remain poorly understood. Herein, we show that TWEAK levels are elevated in PD serum compared to controls. Moreover, using both U373 human astrocyte cells and primary mouse astrocytes, we demonstrate that TWEAK induces mitochondrial oxidative stress as well as protein kinase C delta (PKCδ) and signal transducer and activator of transcription 3 (STAT3) activation, accompanied by NLRC4 inflammasome activation and upregulation and release of proinflammatory cytokines, including IL-1β, TNF-α, and IL-18. Mechanistically, TWEAK-induced PKCδ activation enhances the STAT3/NLRC4 signaling pathway and other proinflammatory mediators through a mitochondrial oxidative stress-dependent mechanism. We further show that PKCδ knockdown and mito-apocynin, a mitochondrial antioxidant, suppress TWEAK-induced proinflammatory NLRC4/STAT3 signaling and cellular oxidative stress response. Notably, we validated our in vitro findings in an MPTP mouse model of PD and in mice receiving intrastriatal administration of TWEAK. These results indicate that TWEAK is a key regulator of astroglial reactivity and illustrate a novel mechanism by which mitochondrial oxidative stress may influence dopaminergic neuronal survival in PD.

Emerging molecular mediators and targets for age-related skeletal muscle atrophy

The age-associated decline in muscle mass has become synonymous with physical frailty among the elderly due to its major contribution in reduced muscle function. Alterations in protein and redox homeostasis along with chronic inflammation, denervation, and hormonal dysregulation are all hallmarks of muscle wasting and lead to clinical sarcopenia in older adults. Reduction in skeletal muscle mass has been observed and reported in the scientific literature for nearly 2 centuries; however, identification and careful examination of molecular mediators of age-related muscle atrophy have only been possible for roughly 3 decades. Here we review molecular targets of recent interest in age-related muscle atrophy and briefly discuss emerging small molecule therapeutic treatments for muscle wasting in sarcopenic susceptible populations.

TWEAK Promotes the Proliferation of Squamous Cell Carcinoma Cells Through Activating cIAP1 Signals

Recent studies showed that tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) induces the proliferation of squamous cell carcinoma (SCC) cells. However, the precise mechanism underlying such effect of TWEAK remains unclear. This study was designed to elucidate the role of cellular inhibitor of apoptosis 1 (cIAP1) in TWEAK-induced proliferation of SCC cells. Human SCC cells (SCC-13, A431, and SCC-9) were cultured in vitro, receiving the stimulation of TWEAK or TNF-related apoptosis-inducing ligand (TRAIL). We found that TWEAK induced cytoplasmic cIAP1 importation and RIP1 ubiquitination in cells, followed by the activation of canonical nuclear factor kappa B signals. MV1, a cIAP1 inhibitor, abrogated TWEAK-induced proliferation of these cells. Moreover, the interaction between TWEAK and its receptor, fibroblast growth factor-inducible 14 (Fn14), enhanced the expression of TRAIL receptor types 3 and 4 (TRAIL-R3/4). Furthermore, the transfection of TRAIL-R3/4 siRNA abrogated the promotion effect of TWEAK on SCC-13 cell proliferation and cIAP1 expression. Therefore, TWEAK/Fn14 interaction promotes the proliferation of SCC cells through activating cIAP1 signals. Targeting the downstream cIAP1 signals might attenuate the effect of TWEAK on SCC cells.

Tumor Necrosis Factor-Like Weak Inducer of Apoptosis (TWEAK)/Fibroblast Growth Factor-Inducible 14 (Fn14) Axis in Cardiovascular Diseases: Progress and Challenges

Cardiovascular diseases (CVD) are the leading cause of mortality in Western countries. CVD include several pathologies, such as coronary artery disease, stroke, peripheral artery disease, and aortic aneurysm, among others. All of them are characterized by a pathological vascular remodeling in which inflammation plays a key role. Interaction between different members of the tumor necrosis factor superfamily and their cognate receptors induce several biological actions that may participate in CVD. The cytokine tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its functional receptor, fibroblast growth factor-inducible 14 (Fn14), are abundantly expressed during pathological cardiovascular remodeling. The TWEAK/Fn14 axis controls a variety of cellular functions, such as proliferation, differentiation, and apoptosis, and has several biological functions, such as inflammation and fibrosis that are linked to CVD. It has been demonstrated that persistent TWEAK/Fn14 activation is involved in both vessel and heart remodeling associated with acute and chronic CVD. In this review, we summarized the role of the TWEAK/Fn14 axis during pathological cardiovascular remodeling, highlighting the cellular components and the signaling pathways that are involved in these processes.

Experimental atopic dermatitis is dependent on the TWEAK/Fn14 signaling pathway

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) acts through its receptor fibroblast growth factor inducible 14 (Fn14), and participates in skin inflammation. Both TWEAK and Fn14 are highly expressed in skin lesions of patients with atopic dermatitis. The purpose of this study was to further explore the effect of Fn14 inhibition on experimental atopic dermatitis. Experimental atopic dermatitis was induced in the wild-type and Fn14 knock-out BALB/c mice. The effect of TWEAK/Fn14 interaction on keratinocytes was studied in an in-vitro model of atopic dermatitis. Fn14 deficiency ameliorates skin lesions in the mice model, accompanied by less infiltration of inflammatory cells and lower local levels of proinflammatory cytokines, including TWEAK, TNF-α and interleukin (IL)-17. Fn14 deficiency also attenuates the up-regulation of TNFR1 in skin lesions of atopic dermatitis. Moreover, topical TWEAK exacerbates skin lesion in the wild-type but not in the Fn14 knock-out mice. In vitro, TWEAK enhances the expressions of IL-17, IL-18 and IFN-γ in keratinocytes under atopic dermatitis-like inflammation. These results suggest that Fn14 deficiency protects mice from experimental atopic dermatitis, involving the attenuation of inflammatory responses and keratinocyte apoptosis. In the context of atopic dermatitis-like inflammation, TWEAK modulates keratinocytes via a TNFR1-mediated pathway.

Tumor Necrosis Factor (TNF) Receptor Expression Determines Keratinocyte Fate upon Stimulation with TNF-Like Weak Inducer of Apoptosis

The interaction between tumor necrosis factor- (TNF-) like weak inducer of apoptosis (TWEAK) and fibroblast growth factor-inducible 14 (Fn14) regulates the fate of keratinocytes, depending on the relative expression of TNF receptor (TNFR) 1 or TNFR2. However, the precise mechanism underlying this TWEAK-mediated regulation remains unclear. The aim of this study was to provide comprehensive insight into the roles of Fn14, TNFR1/2, and other relevant molecules in the fate of keratinocytes. Further, we sought to elucidate the structural basis for the interaction of TWEAK and Fn14 in regulating cellular outcomes. Normal keratinocytes (mainly expressing TNFR1) and TNFR2-overexpressing keratinocytes were stimulated with TWEAK. Through immunoprecipitation and Western blotting of keratinocyte lysates, we elucidated the associations between Fn14, TNFR-associated factor 2 (TRAF2), cellular inhibitor of apoptosis protein 1 (cIAP1), and TNFR1/2 molecules. Additionally, we found that TRAF2 exhibited binding to Fn14, cIAP1, and TNFR1/2. Our data suggest that TWEAK induces apoptosis in normal keratinocytes and proliferation in TNFR2-overexpressing keratinocytes in a TNF-α-independent manner; however, inhibition of TRAF2 appears to reverse this effect. Interestingly, the interaction between TWEAK and Fn14 increased TNFR1-associated death domain protein and caspase-8 expression in normal keratinocytes and promoted cytoplasmic import of cIAP1 in TNFR2-overexpressing keratinocytes. In conclusion, we found that the Fn14-TRAF2-TNFR signaling axis mediates TWEAK's regulation of the fate of keratinocytes, possibly in a manner involving the TNF-α-independent TNFR signal transduction.

Hepatic progenitor cell activation is induced by the depletion of the gut microbiome in mice

The homeostasis of the gut microbiome is crucial for human health and for liver function. However, it has not been established whether the gut microbiome influence hepatic progenitor cells (HPCs). HPCs are capable of self‐renewal and differentiate into hepatocytes and cholangiocytes; however, HPCs are normally quiescent and are rare in adults. After sustained liver damage, a ductular reaction occurs, and the number of HPCs is substantially increased. Here, we administered five broad‐spectrum antibiotics for 14 days to deplete the gut microbiomes of male C57BL/6 mice, and we measured the plasma aminotransferases and other biochemical indices. The expression levels of two HPC markers, SRY‐related high mobility group‐box gene 9 (Sox9) and cytokeratin (CK), were also measured. The plasma aminotransferase activities were not affected, but the triglyceride, lactate dehydrogenase, low‐density lipoprotein, and high‐density lipoprotein concentrations were significantly altered; this suggests that liver function is affected by the composition of the gut microbiome. The mRNA expression of Sox9 was significantly higher in the treated mice than it was in the control mice (p < 0.0001), and a substantial expression of Sox9 and CK was observed around the bile ducts. The mRNA expression levels of proinflammatory factors (interleukin [IL]‐1β, IL‐6, tumor necrosis factor [TNF]‐α, and TNF‐like weak inducer of apoptosis [Tweak]) were also significantly higher in the antibiotic‐treated mice than the levels in the control mice. These data imply that the depletion of the gut microbiome leads to liver damage, negatively impacts the hepatic metabolism and function, and activates HPCs. However, the underlying mechanisms remain to be determined.

TRAIL, OPG, and TWEAK in kidney disease: biomarkers or therapeutic targets?

Ligands and receptors of the tumor necrosis factor (TNF) superfamily regulate immune responses and homeostatic functions with potential diagnostic and therapeutic implications. Kidney disease represents a global public health problem, whose prevalence is rising worldwide, due to the aging of the population and the increasing prevalence of diabetes, hypertension, obesity, and immune disorders. In addition, chronic kidney disease is an independent risk factor for the development of cardiovascular disease, which further increases kidney-related morbidity and mortality. Recently, it has been shown that some TNF superfamily members are actively implicated in renal pathophysiology. These members include TNF-related apoptosis-inducing ligand (TRAIL), its decoy receptor osteoprotegerin (OPG), and TNF-like weaker inducer of apoptosis (TWEAK). All of them have shown the ability to activate crucial pathways involved in kidney disease development and progression (e.g. canonical and non-canonical pathways of the transcription factor nuclear factor-kappa B), as well as the ability to regulate cell proliferation, differentiation, apoptosis, necrosis, inflammation, angiogenesis, and fibrosis with double-edged effects depending on the type and stage of kidney injury. Here we will review the actions of TRAIL, OPG, and TWEAK on diabetic and non-diabetic kidney disease, in order to provide insights into their full clinical potential as biomarkers and/or therapeutic options against kidney disease.

Decrease in inflammatory biomarker concentration by intervention with selenium and coenzyme Q10: a subanalysis of osteopontin, osteoprotergerin, TNFr1, TNFr2 and TWEAK

Background

Inflammation is central to the pathogenesis of many diseases. Supplementation with selenium and coenzyme Q10 has been shown to reduce cardiovascular mortality, and increase cardiac function in elderly persons with a low intake of selenium. There are indications that one of the mechanisms of this positive effect is a decrease in inflammation.

Methods

Osteopontin, osteoprotegerin, sTNF receptor 1, sTNF receptor 2 and the tumor necrosis factor-like weak inducer of apoptosis called TWEAK, were determined in plasma after 6 months and 42 months in 219 community-living elderly persons, of whom 119 received supplements of selenium (200 μg/day) and coenzyme Q10 (200 mg/day), and 101 received a placebo. Repeated measures of variance were used to evaluate the levels, and the results were validated through ANCOVA analyses with adjustments for important covariates.

Results

Significantly lower concentrations of four of the five biomarkers for inflammation were observed as a result of the intervention with the supplements. Only TWEAK did not show significant differences.

Conclusion

In this sub-analysis of the intervention with selenium and coenzyme Q10 or placebo in an elderly community-living population, biomarkers for inflammation were evaluated. A significantly lower concentration in four of the five biomarkers tested could be demonstrated as a result of the supplementation, indicating a robust effect on the inflammatory system. The decrease in inflammation could be one of the mechanisms behind the positive clinical results on reduced cardiovascular morbidity and mortality reported earlier as a result of the intervention. The study is small and should be regarded as hypothesis-generating, but nonetheless adds important data about mechanisms presently known to increase the risk of clinical effects such as reduced cardiovascular mortality, increased cardiac function and better health-related quality of life scoring, as previously demonstrated in the active treatment group .

Trial registration

The intervention study was registered at Clinicaltrials.gov, and has the identifier NCT01443780 and registered on 09/30/2011.

Reverse Signaling of Tumor Necrosis Factor Superfamily Proteins in Macrophages and Microglia: Superfamily Portrait in the Neuroimmune Interface

The tumor necrosis factor (TNF) superfamily (TNFSF) is a protein superfamily of type II transmembrane proteins commonly containing the TNF homology domain. The superfamily contains more than 20 protein members, which can be released from the cell membrane by proteolytic cleavage. Members of the TNFSF function as cytokines and regulate diverse biological processes, including immune responses, proliferation, differentiation, apoptosis, and embryogenesis, by binding to TNFSF receptors. Many TNFSF proteins are also known to be responsible for the regulation of innate immunity and inflammation. Both receptor-mediated forward signaling and ligand-mediated reverse signaling play important roles in these processes. In this review, we discuss the functional expression and roles of various reverse signaling molecules and pathways of TNFSF members in macrophages and microglia in the central nervous system (CNS). A thorough understanding of the roles of TNFSF ligands and receptors in the activation of macrophages and microglia may improve the treatment of inflammatory diseases in the brain and periphery. In particular, TNFSF reverse signaling in microglia can be exploited to gain further insights into the functions of the neuroimmune interface in physiological and pathological processes in the CNS.

Hyperoside decreases the apoptosis and autophagy rates of osteoblast MC3T3‑E1 cells by regulating TNF‑like weak inducer of apoptosis and the p38mitogen activated protein kinase pathway

Wear particles generated between the interface of joints and artificial joint replacements are one of the primary causes of aseptic loosening. The aim of the present study was to investigate the influence of titanium (Ti) particles on the apoptosis and autophagy of osteoblasts, and probe into the potential use of hyperoside (Hy) as a protector for osteoblasts in Ti particle-induced injury. MC3T3-E1 cells were divided into control, Ti, Hy-1+Ti and Hy-2+Ti groups. Cell viability was detected using a Cell Counting Kit-8 assay. Apoptosis and autophagy rates were determined using flow cytometry. Expression levels of apoptosis-associated genes, including caspase-3, apoptosis regulator BAX, apoptosis regulator Bcl-2 and cellular tumor antigen p53, in addition to autophagy-associated genes, including Beclin1 and microtubule-associated protein light chain 3 conversion LC3-II/I, were measured using reverse transcription-quantitative polymerase chain reaction and western blotting. Activation of the tumor necrosis factor ligand superfamily member 12 (TWEAK)-mitogen activated protein kinase 11 (p38) mitogen activated protein kinase (MAPK) pathway was observed by western blotting. The present study demonstrated that pretreatment with Hy was able to increase cell viability and proliferation, and decrease apoptosis and autophagy to protect MC3T3-E1 cells against Ti particle-induced damage. Activation of the TWEAK-p38 pathway contributed to the repair processes of treatment with Hy. The present results suggested that Hy protected osteoblasts against Ti particle-induced damage by regulating the TWEAK-p38 pathway, which suggested the potential of Hy as a protective agent for bones.

Human and Murine Evidence for Mechanisms Driving Autoimmune Photosensitivity

Ultraviolet (UV) light is an important environmental trigger for systemic lupus erythematosus (SLE) patients, yet the mechanisms by which UV light impacts disease are not fully known. This review covers evidence in both human and murine systems for the impacts of UV light on DNA damage, apoptosis, autoantigen exposure, cytokine production, inflammatory cell recruitment, and systemic flare induction. In addition, the role of the circadian clock is discussed. Evidence is compared in healthy individuals and SLE patients as well as in wild-type and lupus-prone mice. Further research is needed into the effects of UV light on cutaneous and systemic immune responses to understand how to prevent UV-light mediated lupus flares.

Fn14 deficiency ameliorates psoriasis-like skin disease in a murine model

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) is a multifunctional cytokine that acts through its receptor fibroblast growth factor-inducible 14 (Fn14). Recent studies demonstrated that the TWEAK/Fn14 signals participate in the development of psoriasis. The purpose of this study was to further explore the effect of Fn14 inhibition on experimental psoriasis. Psoriasis-like skin disease was induced in the wild-type and Fn14-knockout BALB/c mice. We found that Fn14 deficiency ameliorates psoriasis-like lesion in this model, accompanied by less inflammatory cell infiltration and proinflammatory cytokine production in lesional skin. The cutaneous expression of TNF receptor type 2 also decreased in the Fn14-deficient mice. Moreover, the topical application of TWEAK exacerbated psoriatic lesion in the wild-type but not in the Fn14-deficient mice. Furthermore, TWEAK promoted the expression of interleukin 8, keratin 17, and epidermal growth factor receptor (EGFR) but inhibited the expression of involucrin in psoriatic keratinocytes in vitro. Interestingly, such effect of TWEAK was abrogated by an EGFR inhibitor (erlotinib). TWEAK also enhances the proliferation and interleukin-6 production of dermal microvascular endothelial cells under psoriatic condition. In conclusion, TWEAK/Fn14 signals contribute to the development of psoriasis, and involves the modulation of resident cells and the transduction of the EGFR pathway. Fn14 inhibition might be a novel therapeutic strategy for patients with psoriasis.

Topical TWEAK Accelerates Healing of Experimental Burn Wounds in Mice

The interaction of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor fibroblast growth factor inducible 14 (Fn14) participates in inflammatory responses, fibrosis, and tissue remodeling, which are central in the repair processes of wounds. Fn14 is expressed in main skin cells including dermal fibroblasts. This study was designed to explore the therapeutic effect of TWEAK on experimental burn wounds and the relevant mechanism underlying such function. Third-degree burns were introduced in two BALB/c mouse strains. Recombinant TWEAK was administrated topically, followed by the evaluation of wound areas and histologic changes. Accordingly, the downstream cytokines, inflammatory cell infiltration, and extracellular matrix synthesis were examined in lesional tissue. Moreover, the differentiation markers were analyzed in cultured human dermal fibroblasts upon TWEAK stimulation. The results showed that topical TWEAK accelerated the healing of burn wounds in wild-type mice but not in Fn14-deficient mice. TWEAK strengthened inflammatory cell infiltration, and exaggerated the production of growth factor and extracellular matrix components in wound areas of wild-type mice. Moreover, TWEAK/Fn14 activation elevated the expression of myofibroblastic differentiation markers, including alpha-smooth muscle actin and palladin, in cultured dermal fibroblasts. Therefore, topical TWEAK exhibits therapeutic effect on experimental burn wounds through favoring regional inflammation, cytokine production, and extracellular matrix synthesis. TWEAK/Fn14 activation induces the myofibroblastic differentiation of dermal fibroblasts, partially contributing to the healing of burn wounds.

BP180 Is Critical in the Autoimmunity of Bullous Pemphigoid

Bullous pemphigoid (BP) is by far the most common autoimmune blistering dermatosis that mainly occurs in the elderly. The BP180 is a transmembrane glycoprotein, which is highly immunodominant in BP. The structure and location of BP180 indicate that it is a significant autoantigen and plays a key role in blister formation. Autoantibodies from BP patients react with BP180, which leads to its degradation and this has been regarded as the central event in BP pathogenesis. The consequent blister formation involves the activation of complement-dependent or -independent signals, as well as inflammatory pathways induced by BP180/anti-BP180 autoantibody interaction. As a multi-epitope molecule, BP180 can cause dermal-epidermal separation via combining each epitope with specific immunoglobulin, which also facilitates blister formation. In addition, some inflammatory factors can directly deplete BP180, thereby leading to fragility of the dermal-epidermal junction and blister formation. This review summarizes recent investigations on the role of BP180 in BP pathogenesis to determine the potential targets for the treatment of patients with BP.