Cholecystokinin Downregulates Psoriatic Inflammation by Its Possible Self-Regulatory Effect on Epidermal Keratinocytes

The Immunology of Psoriasis-Current Concepts in Pathogenesis

Psoriasis is one of the most common inflammatory skin diseases with a chronic, relapsing-remitting course. The last decades of intense research uncovered a pathological network of interactions between immune cells and other types of cells in the pathogenesis of psoriasis. Emerging evidence indicates that dendritic cells, TH17 cells, and keratinocytes constitute a pathogenic triad in psoriasis. Dendritic cells produce TNF-α and IL-23 to promote T cell differentiation toward TH17 cells that produce key psoriatic cytokines IL-17, IFN-γ, and IL-22. Their activity results in skin inflammation and activation and hyperproliferation of keratinocytes. In addition, other cells and signaling pathways are implicated in the pathogenesis of psoriasis, including TH9 cells, TH22 cells, CD8+ cytotoxic cells, neutrophils, γδ T cells, and cytokines and chemokines secreted by them. New insights from high-throughput analysis of lesional skin identified novel signaling pathways and cell populations involved in the pathogenesis. These studies not only expanded our knowledge about the mechanisms of immune response and the pathogenesis of psoriasis but also resulted in a revolution in the clinical management of patients with psoriasis. Thus, understanding the mechanisms of immune response in psoriatic inflammation is crucial for further studies, the development of novel therapeutic strategies, and the clinical management of psoriasis patients. The aim of the review was to comprehensively present the dysregulation of immune response in psoriasis with an emphasis on recent findings. Here, we described the role of immune cells, including T cells, B cells, dendritic cells, neutrophils, monocytes, mast cells, and innate lymphoid cells (ILCs), as well as non-immune cells, including keratinocytes, fibroblasts, endothelial cells, and platelets in the initiation, development, and progression of psoriasis.

Somatostatin Receptor 2 in 10 Different Types of Human Non-Neoplastic Gastrointestinal Neuroendocrine Cells

Somatostatin is known to inhibit the secretion of various hormones by acting on endocrine cells through the somatostatin receptor 2 (SSTR2). Immunohistochemical evaluation of SSTR2 has become increasingly important in clinical practice to determine treatment strategies for patients with a neuroendocrine tumor (NET). Gastrointestinal (GI) tracts contain various neuroendocrine cells that constitute a diffuse endocrine system and some NETs are derived from those cells. In addition, NETs have been well known to express a variable spectrum of proteins shared by their normal cell counterparts of the specific anatomical sites. Thus, we may derive the kinetics of SSTR2 expression of NETs, including de novo expression, from the SSTR2 expression of the corresponding normal neuroendocrine cells. Therefore, a detailed study on the distribution of SSTR2 in normal human neuroendocrine cells may contribute to understanding the expression of SSTR2 in GI-NETs. However, the detailed cellular localization of SSTR2 in non-neoplastic neuroendocrine cells remains unknown. Therefore, we immunolocalized SSTR2 in neuroendocrine cells of normal human GI tracts, including the stomach, duodenum, ileum, and rectum, obtained from 41 surgically resected tissue specimens. Double immunohistochemistry of SSTR2 and hormones or hormone-associated proteins was performed. In all GI neuroendocrine cells, cell types other than D- and EC-cells demonstrated a high percentage of SSTR2-positive cases or a high double-positive ratio. In particular, EC-cells showed lower SSTR2-positive ratios in all sites. Midgut NETs, which often produce serotonin, are excellent targets for somatostatin analogs and are positive for SSTR2. Thus, we speculated that EC-cell NETs might lead to the de novo expression of SSTR2. In addition, a previous report showed high SSTR2 expression in ECL-cell NETs and gastrinomas, which could be because they are derived from neuroendocrine cells with high SSTR2 expression. This study may contribute to understanding the expression of SSTR2 in GI-NETs.

CCK regulates osteogenic differentiation through TNFα/NF-κB in peri-implantitis

OBJECTIVE

Peri-implantitis is characterized by peri-implant mucositis and alveolar bone resorption. This study investigated cholecystokinin (CCK) expression and the mechanism underlying its involvement in peri-implantitis.

METHODS

mRNA sequencing was performed using the Gene Expression Omnibus database GSE106090. Human bone marrow mesenchymal stem cells (hBMSCs) were pretreated with various concentrations of CCK (0, 10, 30, or 100 nM) for 1 hour before induction in osteogenic differentiation medium for 2 weeks. Alkaline phosphatase (ALP) activity was determined, and the cells were stained with alizarin red. The expression levels of TNFα and the osteogenic markers ALP, RUNX2, and OCN were measured using quantitative real-time PCR. TNFα, phosphorylated P65, and total P65 levels were determined by western blot.

RESULTS

Compared with healthy individuals, 262 and 215 genes were up- and down-regulated, respectively, in the periodontal tissues of patients with peri-implantitis. CCK expression was significantly upregulated in patients with peri-implantitis. CCK reduced ALP activity, osteogenic differentiation, and levels of the osteogenic markers ALP, RUNX2, and OCN. Moreover, CCK promoted levels of TNFα and phosphorylated P65, which is a marker of activation for the NF-κB inflammatory pathway.

CONCLUSIONS

CCK regulates osteogenic differentiation through the TNFα/NF-κB axis in peri-implantitis.

Cholecystokinin receptor antagonist suppresses melanoma growth by inducing apoptosis of tumor cells

Melanoma is a malignant skin tumor with high metastatic activity. Although melanoma has been well-studied, its cellular kinetics remain elusive. The cholecystokinin (CCK) receptor is expressed in various types of tumors because CCK promotes the survival and proliferation of tumor cells. Thus, we hypothesized that the growth of melanoma was positively regulated by signals from the CCK receptor and sought to investigate whether CCK receptor antagonists affect the growth of melanoma cells expressing CCK receptor. Immunohistochemically, the CCK receptor A is expressed in the clinical specimens of melanoma. CCK receptor antagonists decreased the viability of melanoma cells by suppressing cell division and promoting apoptosis. CCK receptor antagonists also decreased the mitochondrial membrane potential through enhanced gene expression of the proapoptotic protein, Bcl2-associated X, and tumor suppressor, p53, suggesting that the antagonist induced the apoptosis of melanoma cells in a mitochondria-dependent manner. In addition, a caspase 3 inhibitor, Z-DEVD-FMK, partially blocked the antiviability of the antagonist, indicating that caspase 3 is involved in antagonist-induced apoptosis. Notably, tumor growth was attenuated when a CCK receptor antagonist was locally administered to the melanoma-bearing mice. Therefore, our study suggests the therapeutic potential of CCK receptor antagonists in the treatment of skin cancer.

Advances in the pathogenesis of psoriasis: from keratinocyte perspective

Psoriasis is a complex long-lasting inflammatory skin disease with high prevalence and associated comorbidity. It is characterized by epidermal hyperplasia and dermal infiltration of immune cells. Here, we review the role of keratinocytes in the pathogenesis of psoriasis, focusing on factors relevant to genetics, cytokines and receptors, metabolism, cell signaling, transcription factors, non-coding RNAs, antimicrobial peptides, and proteins with other different functions. The critical role of keratinocytes in initiating and maintaining the inflammatory state suggests the great significance of targeting keratinocytes for the treatment of psoriasis.

The hair follicle-psoriasis axis: Shared regulatory mechanisms and therapeutic targets

It has long been known that there is a special affinity of psoriasis for the scalp: Here, it occurs most frequently, lesions terminate sharply in frontal skin beyond the hair line and are difficult to treat. Yet, surprisingly, scalp psoriasis only rarely causes alopecia, even though the pilosebaceous unit clearly is affected. Here, we systematically explore the peculiar, insufficiently investigated connection between psoriasis and growing (anagen) terminal scalp hair follicles (HFs), with emphasis on shared regulatory mechanism and therapeutic targets. Interestingly, several drugs and stressors that can trigger/aggravate psoriasis can inhibit hair growth (e.g. beta-blockers, chloroquine, carbamazepine, interferon-alpha, perceived stress). Instead, several anti-psoriatic agents can stimulate hair growth (e.g. cyclosporine, glucocorticoids, dithranol, UV irradiation), while skin/HF trauma (Köbner phenomenon/depilation) favours the development of psoriatic lesions and induces anagen in "quiescent" (telogen) HFs. On this basis, we propose two interconnected working models: (a) the existence of a bidirectional "hair follicle-psoriasis axis," along which keratinocytes of anagen scalp HFs secrete signals that favour the development and maintenance of psoriatic scalp lesions and respond to signals from these lesions, and (b) that anagen induction and psoriatic lesions share molecular "switch-on" mechanisms, which invite pharmacological targeting, once identified. Therefore, we advocate a novel, cross-fertilizing and integrative approach to psoriasis and hair research that systematically characterizes the "HF-psoriasis axis," focused on identification and therapeutic targeting of selected, shared signalling pathways in the future management of both, psoriasis and hair growth disorders.

Methylene Blue Application to Lessen Pain: Its Analgesic Effect and Mechanism

Methylene blue (MB) is a cationic thiazine dye, widely used as a biological stain and chemical indicator. Growing evidence have revealed that MB functions to restore abnormal vasodilation and notably it is implicated even in pain relief. Physicians began to inject MB into degenerated disks to relieve pain in patients with chronic discogenic low back pain (CDLBP), and some of them achieved remarkable outcomes. For osteoarthritis and colitis, MB abates inflammation by suppressing nitric oxide production, and ultimately relieves pain. However, despite this clinical efficacy, MB has not attracted much public attention in terms of pain relief. Accordingly, this review focuses on how MB lessens pain, noting three major actions of this dye: anti-inflammation, sodium current reduction, and denervation. Moreover, we showed controversies over the efficacy of MB on CDLBP and raised also toxicity issues to look into the limitation of MB application. This analysis is the first attempt to illustrate its analgesic effects, which may offer a novel insight into MB as a pain-relief dye.

Pathophysiology of Skin Resident Memory T Cells

Tissue resident memory T (T_RM) cells reside in peripheral, non-lymphoid tissues such as the skin, where they act as alarm-sensor cells or cytotoxic cells. Physiologically, skin T_RM cells persist for a long term and can be reactivated upon reinfection with the same antigen, thus serving as peripheral sentinels in the immune surveillance network. CD8⁺CD69⁺CD103⁺ T_RM cells are the well-characterized subtype that develops in the epidermis. The local mediators such as interleukin (IL)-15 and transforming growth factor (TGF)-β are required for the formation of long-lived T_RM cell population in skin. Skin T_RM cells engage virus-infected cells, proliferate in situ in response to local antigens and do not migrate out of the epidermis. Secondary T_RM cell populations are derived from pre-existing T_RM cells and newly recruited T_RM precursors from the circulation. In addition to microbial pathogens, topical application of chemical allergen to skin causes delayed-type hypersensitivity and amplifies the number of antigen-specific CD8⁺ T_RM cells at challenged site. Skin T_RM cells are also involved in the pathological conditions, including vitiligo, psoriasis, fixed drug eruption and cutaneous T-cell lymphoma (CTCL). The functions of these T_RM cells seem to be different, depending on each pathology. Psoriasis plaques are seen in a recurrent manner especially at the originally affected sites. Upon stimulation of the skin of psoriasis patients, the CD8⁺CD103⁺CD49a^- T_RM cells in the epidermis seem to be reactivated and initiate IL-17A production. Meanwhile, autoreactive CD8⁺CD103⁺CD49a⁺ T_RM cells secreting interferon-γ are present in lesional vitiligo skin. Fixed drug eruption is another disease where skin T_RM cells evoke its characteristic clinical appearance upon administration of a causative drug. Intraepidermal CD8⁺ T_RM cells with an effector-memory phenotype resident in the skin lesions of fixed drug eruption play a major contributing role in the development of localized tissue damage. CTCL develops primarily in the skin by a clonal expansion of a transformed T_RM cells. CD8⁺ CTCL with the pagetoid epidermotropic histology is considered to originate from epidermal CD8⁺ T_RM cells. This review will discuss the current understanding of skin T_RM biology and their contribution to skin homeostasis and diseases.

A promising therapeutic target for psoriasis: Neuropeptides in human skin

Psoriasis is a chronic inflammatory skin disease featured by excessive proliferation of keratinocytes, clearly defined round erythema and dry, scaly plaques, long-term inflammatory cells infiltration in skin lesions. However, the physiopathological mechanism of psoriasis is still not clearly understood. Neuropeptides, a class of peptides secreted by the nervous system, may play important roles in promoting excessive proliferation of keratinocyte, enhancing angiogenesis, vasodilation, plasma extravasation and chemotaxis of inflammatory cells during the development of psoriasis. To understand the pathogenesis of neuropeptides in psoriasis, we summarized the function of several common neuropeptides in psoriasis and hypothesize neuropeptides may serve as therapeutic potential novel targets in psoriasis.

Preventative effects of the partial RANKL peptide MHP1-AcN in a mouse model of imiquimod-induced psoriasis

We recently developed a partial peptide of receptor activator of nuclear factor-кB ligand (RANKL) known as microglial healing peptide 1 (MHP1-AcN), that inhibits Toll-like receptor (TLR)-related inflammation through RANKL/RANK signaling in microglia and macrophages without promoting osteoclast activation. The abnormal activation of TLRs contributes to the initiation and maintenance of psoriasis, which is a chronic inflammatory skin disease that involves the aberrant expression of proinflammatory cytokines and the subsequent dermal γδ T cell and T helper 17 (Th17) cell responses. The inhibition of TLR-mediated inflammation provides an important strategy to treat psoriasis. Here, we examined the preventative effects of MHP1-AcN in a mouse model of imiquimod (a TLR 7/8 agonist)-induced psoriasis. Topical imiquimod application induced psoriasis-like skin lesions on the ear and dorsal skin. Systemic administration of MHP1-AcN by daily subcutaneous injection significantly prevented the development of skin lesions, including erythema, scaling and thickening. Mice treated with MHP1-AcN showed reduced levels of skin Il6 mRNA at 32 h and reduced levels of Il23 and Il17a mRNA at d9. Serum levels of IL-6 and IL-23 were reduced at 32 h, and IL-17A was reduced at d9. These results indicated that MHP1-AcN could decrease imiquimod-induced IL-6, IL-23 and IL-17A production. MHP1-AcN is potentially an alternative treatment for psoriasis.