Blockade of TNF receptor superfamily 1 (TNFR1)-dependent and TNFR1-independent cell death is crucial for normal epidermal differentiation

Necroptosis and Its Involvement in Various Diseases

Necroptosis is a regulated form of cell death involved in the development of various pathological conditions. In contrast to apoptosis, plasma membrane rupture (PMR) occurs in cells in the relatively early stage of necroptosis; therefore, necroptosis induces a strong inflammatory response. Stimuli, including tumor necrosis factor (TNF), interferon (IFN)α/β, lipopolysaccharide, polyI:C, and viral infection, induce the formation of necrosomes that lead to membrane rupture and the release of intracellular contents, termed danger-associated molecular patterns (DAMPs). DAMPs are the collective term for molecules that normally reside in the cytoplasm or nucleus in living cells without inducing inflammation but induce strong inflammatory responses when released outside cells. Recent studies have provided a better understanding of the mechanisms underlying PMR and the release of DAMPs. Moreover, necroptosis is involved in various pathological conditions, and mutations in necroptosis-related genes can cause hereditary autoinflammatory syndromes. Thus, manipulating necroptosis signaling pathways may be useful for treating diseases involving necroptosis.

Composite Hydrogels with Embedded Silver Nanoparticles and Ibuprofen as Wound Dressing

The wound healing process is often slowed down as a result of complications from bacterial infections and inflammatory reactions. Therefore, it is necessary to develop dressings with fast antibacterial and anti-inflammatory activity that shorten the wound healing period by promoting cell migration and proliferation. Chitosan (CS)-based hydrogels have been widely studied for their antibacterial and wound healing capabilities. Herein, we developed a composite hydrogel based on CS and PVA embedding silver nanoparticles (AgNPs) with antibacterial properties and ibuprofen (Ib) as an anti-inflammatory agent. The hydrogel prepared by double physical cross-linking, with oxalic acid and by freeze-thawing, loaded with 0.225 wt.% AgNPs and 0.264 wt.% Ib, displayed good mechanical properties (compressive modulus = 132 kPa), a high swelling degree and sustained drug delivery (in simulated skin conditions). Moreover, the hydrogel showed strong antibacterial activity against S. aureus and K. pneumoniae due to the embedded AgNPs. In vivo, this hydrogel accelerated the wound regeneration process through the enhanced expression of TNF alpha IP8, by activating downstream cascades and supporting the healing process of inflammation; Cox2, which enhances the migration and proliferation of cells involved in re-epithelization and angiogenesis; MHCII, which promotes immune cooperation between local cells, eliminating dead tissue and controlling infection; the intense expression of Col I as a major marker in the tissue granulation process; and αSMA, which marks the presence of myofibroblasts involved in wound closure and indicates ongoing re-epithelization. The results reveal the potential healing effect of CS/PVA/AgNPs/Ib hydrogels and suggest their potential use as wound dressings.

Effect of celecoxib administration on the skin of 40-week-old mice

Various side effects associated with the use of nonsteroidal anti-inflammatory drugs (NSAIDs) in analgesia have been reported. Among the NSAIDs, celecoxib has fewer side effects and is often used in therapeutic applications. However, the effect of celecoxib on aged skin is unknown. In this study, we investigated the effects of celecoxib administration on the skin of aged mice. We analyzed a 40-week-old mouse model and a 10-week-old mice as the control group. The animals were orally administered celecoxib for four consecutive days and then killed and dissected the day after the last dose. In aged mice treated with celecoxib, the water content of the stratum corneum, which is one of the markers of dry skin, was lower than that in the control and young mice groups. In addition, serum hyaluronic acid, creatinine, and inflammatory cytokines in the collected blood samples of aged mice were elevated compared to those in other mice groups, suggesting the onset of acute renal injury. Therefore, it was considered that acute renal injury occurred from the administration of celecoxib to aged mice, whereas dry skin developed by the promotion of inflammatory cytokine secretion and release into the bloodstream in this group.

Cellular Heterogeneity and Plasticity of Skin Epithelial Cells in Wound Healing and Tumorigenesis

Cellular differentiation, the fundamental hallmark of cells, plays a critical role in homeostasis. And stem cells not only regulate the process where embryonic stem cells develop into a complete organism, but also replace ageing or damaged cells by proliferation, differentiation and migration. In characterizing distinct subpopulations of skin epithelial cells, stem cells show large heterogeneity and plasticity for homeostasis, wound healing and tumorigenesis. Epithelial stem cells and committed progenitors replenish each other or by themselves owing to the remarkable plasticity and heterogeneity of epidermal cells under certain circumstance. The development of new assay methods, including single-cell RNA sequence, lineage tracing assay, intravital microscopy systems and photon-ablation assay, highlight the plasticity of epidermal stem cells in response to injure and tumorigenesis. However, the critical mechanisms and key factors that regulate cellular plasticity still need for further exploration. In this review, we discuss the recent insights about the heterogeneity and plasticity of epithelial stem cells in homeostasis, wound healing and skin tumorigenesis. Understanding how stem cells collaborate together to repair injury and initiate tumor will offer new solutions for relevant diseases. Schematic abstract of cellular heterogeneity and plasticity of skin epithelial cells in wound healing and tumorigenesis.

Indomethacin, a non-steroidal anti-inflammatory drug, induces skin dryness via PPARγ in mice

Cyclooxygenase (COX)-1-selective inhibitors have side effects such as itching and dryness of the skin. In this study, the degree of skin dryness and the onset mechanism of this condition were investigated by comparing the effects of three non-steroidal anti-inflammatory drugs (NSAIDs) in mice. Mice were orally administered either indomethacin, loxoprofen sodium, or celecoxib (n = 5 per group) once daily for four consecutive days, and blood samples as well as skin and jejunal tissues were isolated on day 5. In the mice treated with indomethacin, transepidermal water loss was significantly increased, and dry skin was observed. In addition, the expression of matrix metalloproteinase (MMP)-I, mast cells, CD163, CD23, CD21, histamine, and peroxisome proliferation-activated receptor (PPAR)γ in the skin and jejunum was increased, and the blood levels of interleukin-10 and immunoglobulin E were also increased. In contrast, the expression of collagen type I in the skin was decreased. These results show that indomethacin activates PPARγ in the skin and jejunum, changes the polarity of macrophages, increases the secretion of MMP-1 from mast cells, and decomposes collagen type I, leading to dry skin.

Proinflammatory cytokines regulate epidermal stem cells in wound epithelialization

The skin, which serves as the first barrier of the human body, is particularly susceptible to exogenous injuries. Skin wounds, including acute burns and chronic non-healing ulcers, are commonly observed in clinics. Healing of skin wounds is a complex process, consisting of infiltration of inflammatory cells, cellular proliferation, and tissue remodeling phases, which restore the integrity and functions of the skin. Epithelialization is involved in wound healing through re-establishing an intact keratinocyte layer. Epidermal stem cells are indispensable for epithelialization, and they are regulated by multiple proinflammatory cytokines or growth factors. In this review, we summarize recent advances in the effect of these cytokines on migration, proliferation, and differentiation processes of epidermal stem cells. We also introduce promising therapeutic strategies targeting epidermal stem cells or related proinflammatory cytokines for patients with skin wounds.

FasL-PDPK1 Pathway Promotes the Cytotoxicity of CD8+ T Cells During Ischemic Stroke

CD8⁺ T cells are recognized as key players in exacerbation of ischemic stroke; however, the underlying mechanism in modulating the function of CD8⁺ T cells has not been completely elucidated. Here, we uncovered that FasL enhanced the cytotoxicity of CD8⁺ T cells to neurons after ischemic stroke. Inactivation of FasL specific on CD8⁺ T cells protected against brain damage and neuron loss. Proteomic analysis identified that PDPK1 functioned downstream of FasL signaling and inhibition of PDPK1 effectively reduced cytotoxicity of CD8⁺ T cells and improved ischemic neurological deficits. Taken together, these results highlight an intrinsic FasL-PDPK1 pathway regulating the cytotoxicity of CD8⁺ T cells in ischemic stroke.

Flavonoids of Tripodanthus acutifolius inhibit TNF-α production in LPS-activated THP-1 and B16-F10 cells

ETHNOPHARMACOLOGICAL RELEVANCE

T. acutifolius is an endemic species from South America which has been used in traditional medicine since ancient times due to its biological properties, including its anti-inflammatory effects.

AIM OF THE STUDY

The aim of the article is to investigate the inhibitory activity of T. acutifolius over TNF-α production in THP-1 and B16-F10 cells. To achieve this, phytochemical analysis has been used to determine the compounds present in the species with anti-inflammatory effects.

MATERIALS AND METHODS

Leaves and stems of T. acutifolius were extracted with n-heptane, dichloromethane, methanol and water. The resulting extracts were analysed in THP-1 and B16-F10 cells by measuring their inhibitory capacity over the production of TNF-α stimulated with LPS.

RESULTS

The guided-bioassay led to the isolation of 6,2',4'-trimethoxyflavone (1), 5,3',4'-trihydroxy-6,7,8-trimethoxyflavone (2), (E)-2',4'-dihydroxy-6'-methoxy-chalcone (3) and 5,4'-dihydroxy-6,7,8-trimethoxyflavone (4) from the dichloromethanic extract. Compounds showed an inhibitory activity of TNF-⍺ production in THP-1 cells, with IC₅₀ of 2.38 ± 0.02 μM, 12.36 ± 0.17 μM, 1.12 ± 0.01 μM and 8.09 ± 0.04 μM, respectively. In addition, the compounds showed an inhibitory activity of TNF-⍺ production in B16-F10 cells with IC₅₀ of 1.32 ± 0.03 μM, 5.63 ± 0.09 μM, 0.60 ± 0.02 μM and 3.77 ± 0.15 μM, respectively.

CONCLUSIONS

We identified 3 flavones (6,2',4'-trimethoxyflavone, 5,3',4'-trihydroxy-6,7,8-trimethoxyflavone, 5,4'-dihydroxy-6,7,8-trimethoxyflavone) and a chalcone ((E)-2',4'-dihydroxy-6'-methoxy-chalcone) present in the leaves and stems of T. acutifolius. These compounds are an alternative for the treatment of immune-mediated inflammatory disorders, acting as negative modulators over the TNF-α production.

Necroptosis of Intestinal Epithelial Cells Induces Type 3 Innate Lymphoid Cell-Dependent Lethal Ileitis

A short form of cellular FLICE-inhibitory protein encoded by CFLARs promotes necroptosis. Although necroptosis is involved in various pathological conditions, the detailed mechanisms are not fully understood. Here we generated transgenic mice wherein CFLARs was integrated onto the X chromosome. All male CFLARs Tg mice died perinatally due to severe ileitis. Although necroptosis was observed in various tissues of CFLARs Tg mice, large numbers of intestinal epithelial cells (IECs) died by apoptosis. Deletion of Ripk3 or Mlkl, essential genes of necroptosis, prevented both necroptosis and apoptosis, and rescued lethality of CFLARs Tg mice. Type 3 innate lymphoid cells (ILC3s) were activated and recruited to the small intestine along with upregulation of interleukin-22 (Il22) in CFLARs Tg mice. Deletion of ILC3s or Il22 rescued lethality of CFLARs Tg mice by preventing apoptosis, but not necroptosis of IECs. Together, necroptosis-dependent activation of ILC3s induces lethal ileitis in an IL-22-dependent manner.

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CFLARs Tg mice develop severe ileitis in utero

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Intestinal epithelial cells die by apoptosis and necroptosis in CFLARs Tg mice

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Blockade of necroptosis rescues lethality of CFLARs Tg mice

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Necroptosis activates type 3 innate lymphoid cells, resulting in severe ileitis