Polycystin-1 downregulation induces ERK-dependent mTOR pathway activation in a cellular model of psoriasis

Therapeutic overview of sudachitin

Citrus fruits are extensively cultivated and eaten both raw and in refined forms. Citrus fruit peels are highly concentrated in polyphenolic substances. This makes them useful resources. Polymethoxyflavones (PMFs), found in citrus peels, belong to a specific subclass of flavonoids where most or all hydroxyl groups are methylated. PMFs have been documented to possess chemopreventive actions, anticancer, anti-inflammatory, and anti-atherosclerosis properties, as well as neuroprotective effects. Sudachitin, a PMF, is primarily found in Citrus sudachi. Japan's Tokushima prefecture is home to this famous fruit. In recent years, there has been a growing interest among researchers in exploring the potential health benefits of sudachitin, spurred by its presence in traditional diets and its association with various positive health outcomes. Studies conducted over the past decade have revealed promising effects of sudachitin in multiple health conditions, including cancer, skin disorders, inflammatory conditions, diabetes, obesity, and neurodegenerative disorders. Although these promising results exist, there is still a need for thorough preclinical and clinical research to confirm sudachitin's effectiveness in treating chronic conditions. This review seeks to summarize animal and cell studies exploring sudachitin's pharmacological properties and the potential molecular pathways underlying its therapeutic effects. Through this, we aim to clarify the clinical potential of sudachitin across various disorders, paving the way for future research and the development of sudachitin-based therapies.

Targeted siRNA Therapy for Psoriasis: Translating Preclinical Potential into Clinical Treatments

Psoriasis is a chronic inflammatory skin disease characterized by the excessive proliferation of keratinocytes and heightened immune activation. Targeting pathogenic genes through small interfering RNA (siRNA) therapy represents a promising strategy for the treatment of psoriasis. This mini-review provides a comprehensive summary of siRNA research targeting the pathogenesis of psoriasis, covering aspects such as keratinocyte function, inflammatory cell roles, preclinical animal studies, and siRNA delivery mechanisms. It details recent advancements in RNA interference that modulate key factors including keratinocyte proliferation (Fibroblast Growth Factor Receptor 2, FGFR2), apoptosis (Interferon Alpha Inducible Protein 6, G1P3), differentiation (Grainyhead Like Transcription Factor 2, GRHL2), and angiogenesis (Vascular Endothelial Growth Factor, VEGF); immune cell infiltration and inflammation (Tumor Necrosis Factor-Alpha, TNF-α; Interleukin-17, IL-17); and signaling pathways (JAK-STAT, Nuclear Factor Kappa B, NF-κB) that govern immunopathology. Despite significant advances in siRNA-targeted treatments for psoriasis, several challenges persist. Continued scientific developments promise the creation of more effective and safer siRNA medications, potentially enhancing the quality of life for psoriasis patients and revolutionizing treatments for other diseases. This article focuses on the most recent research advancements in targeting the pathogenesis of psoriasis with siRNA and explores its future therapeutic prospects.

Runx2 and Polycystins in Bone Mechanotransduction: Challenges for Therapeutic Opportunities

Bone mechanotransduction is a critical process during skeletal development in embryogenesis and organogenesis. At the same time, the type and level of mechanical loading regulates bone remodeling throughout the adult life. The aberrant mechanosensing of bone cells has been implicated in the development and progression of bone loss disorders, but also in the bone-specific aspect of other clinical entities, such as the tumorigenesis of solid organs. Novel treatment options have come into sight that exploit the mechanosensitivity of osteoblasts, osteocytes, and chondrocytes to achieve efficient bone regeneration. In this regard, runt-related transcription factor 2 (Runx2) has emerged as a chief skeletal-specific molecule of differentiation, which is prominent to induction by mechanical stimuli. Polycystins represent a family of mechanosensitive proteins that interact with Runx2 in mechano-induced signaling cascades and foster the regulation of alternative effectors of mechanotransuction. In the present narrative review, we employed a PubMed search to extract the literature concerning Runx2, polycystins, and their association from 2000 to March 2024. The keywords stated below were used for the article search. We discuss recent advances regarding the implication of Runx2 and polycystins in bone remodeling and regeneration and elaborate on the targeting strategies that may potentially be applied for the treatment of patients with bone loss diseases.

Pathophysiological Roles of Ion Channels in Epidermal Cells, Immune Cells, and Sensory Neurons in Psoriasis

Psoriasis is a chronic inflammatory skin disease characterized by the rapid abnormal growth of skin cells in the epidermis, driven by an overactive immune system. Consequently, a complex interplay among epidermal cells, immune cells, and sensory neurons contributes to the development and progression of psoriasis. In these cellular contexts, various ion channels, such as acetylcholine receptors, TRP channels, Ca2+ release-activated channels, chloride channels, and potassium channels, each serve specific functions to maintain the homeostasis of the skin. The dysregulation of ion channels plays a major role in the pathophysiology of psoriasis, affecting various aspects of epidermal cells, immune responses, and sensory neuron signaling. Impaired function of ion channels can lead to altered calcium signaling, inflammation, proliferation, and sensory signaling, all of which are central features of psoriasis. This overview summarizes the pathophysiological roles of ion channels in epidermal cells, immune cells, and sensory neurons during early and late psoriatic processes, thereby contributing to a deeper understanding of ion channel involvement in the interplay of psoriasis and making a crucial advance toward more precise and personalized approaches for psoriasis treatment.

Detoxified pneumolysin derivative ΔA146Ply inhibits autophagy and induces apoptosis in acute myeloid leukemia cells by activating mTOR signaling

Leukemia is caused by the malignant clonal expansion of hematopoietic stem cells, and in adults, the most common type of leukemia is acute myeloid leukemia (AML). Autophagy inhibitors are often used in preclinical and clinical models in leukemia therapy. However, clinically available autophagy inhibitors and their efficacy are very limited. More effective and safer autophagy inhibitors are urgently needed for leukemia therapy. In a previous study, we showed that ΔA146Ply, a mutant of pneumolysin that lacks hemolytic activity, inhibited autophagy of triple-negative breast cancer cells by activating mannose receptor (MR) and toll-like receptor 4 (TLR4) and that tumor-bearing mice tolerated ΔA146Ply well. Whether this agent affects AML cells expressing TLR4 and MR and the related mechanisms remain to be determined. In this study, we found that ΔA146Ply inhibited autophagy and induced apoptosis in AML cells. A mechanistic study showed that ΔA146Ply inhibited autophagy by activating mammalian target of rapamycin signaling and induced apoptosis by inhibiting autophagy. ΔA146Ply also inhibited autophagy and induced apoptosis in a mouse model of AML. Furthermore, the combination of ΔA146Ply and chloroquine synergistically inhibited autophagy and induced apoptosis in vitro and in vivo. Overall, this study provides an alternative effective autophagy inhibitor that may be used for leukemia therapy.

A mutated form of the bacterial protein pneumolysin offers a new approach to treating acute myeloid leukemia (AML), due to its ability to stimulate cancer cells to undergo a form of cell suicide called apoptosis. Researchers in China led by Xuemei Zhang at Chongquing Medical University studied the effects of a pneumolysin derivative on cultured human and mouse AML cells. They identified the mechanism by which this derivative activates a known molecular signaling system to inhibit the process of autophagy, in which cells routinely ‘clean up’ degraded or unnecessary components during normal maintenance. This inhibition of autophagy then induced the apoptosis that killed cancer cells. The effect became more pronounced when the pneumolysin derivative was combined with the existing autophagy-inhibiting drug chloroquine. The new combination could be safer and more effective than using chloroquine alone.

LncRNA AGXT2L1-2:2 facilitates keratinocytes proliferation and inhibits apoptosis by interacting with estrogen-related receptor alpha in psoriasis

Our previous studies have revealed that long noncoding RNA (lncRNA) AGXT2L1-2:2 was highly expressed in keratinocytes of psoriasis. However, the functions of lnc-AGXT2L1-2:2 in keratinocytes remain unknown. Meanwhile, co-expression network analysis indicated lnc-AGXT2L1-2:2 could interact with estrogen-related receptor alpha (ERRα). In this study, interleukin (IL)-17A could stimulate the production of lnc-AGXT2L1-2:2 in keratinocytes, thus establishing an in vitro cellular model of psoriasis. Lnc-AGXT2L1-2:2 was overexpressed using lentiviral-vector and ERRα was downregulated with small interfering RNA. Then the effects of lnc-AGXT2L1-2:2 and ERRα on viability, apoptosis, and cell cycle in IL-17A-stimulated keratinocytes were assessed by CCK-8, EdU assay, and flow cytometry. We found that lnc-AGXT2L1-2:2 and ERRα both resulted in higher proliferation ability, lower apoptosis rates, and reduction of G0/G1 phase proportion. Furthermore, lnc-AGXT2L1-2:2 could promote the expression of ERRα and siERRα antagonized the effects of lnc-AGXT2L1-2:2 on the phenotypes above in IL-17A-induced keratinocytes. In conclusion, lnc-AGXT2L1-2:2 was found to promote keratinocytes proliferation, inhibit cell apoptosis and the effects of lnc-AGXT2L1-2:2 on keratinocytes are dependent on ERRα.

Polycystin‐1 regulates cell proliferation and migration through AKT/mTORC2 pathway in a human craniosynostosis cell model

Craniosynostosis is the premature fusion of skull sutures and has a severe pathological impact on childrens’ life. Mechanical forces are capable of triggering biological responses in bone cells and regulate osteoblastogenesis in cranial sutures, leading to premature closure. The mechanosensitive proteins polycystin‐1 (PC1) and polycystin‐2 (PC2) have been documented to play an important role in craniofacial proliferation and development. Herein, we investigated the contribution of PC1 to the pathogenesis of non‐syndromic craniosynostosis and the associated molecular mechanisms. Protein expression of PC1 and PC2 was detected in bone fragments derived from craniosynostosis patients via immunohistochemistry. To explore the modulatory role of PC1 in primary cranial suture cells, we further abrogated the function of PC1 extracellular mechanosensing domain using a specific anti‐PC1 IgPKD1 antibody. Effect of IgPKD1 treatment was evaluated with cell proliferation and migration assays. Activation of PI3K/AKT/mTOR pathway components was further detected via Western blot in primary cranial suture cells following IgPKD1 treatment. PC1 and PC2 are expressed in human tissues of craniosynostosis. PC1 functional inhibition resulted in elevated proliferation and migration of primary cranial suture cells. PC1 inhibition also induced activation of AKT, exhibiting elevated phospho (p)‐AKT (Ser473) levels, but not 4EBP1 or p70S6K activation. Our findings indicate that PC1 may act as a mechanosensing molecule in cranial sutures by modulating osteoblastic cell proliferation and migration through the PC1/AKT/mTORC2 cascade with a potential impact on the development of non‐syndromic craniosynostosis.

Predominant Role of mTOR Signaling in Skin Diseases with Therapeutic Potential

The serine/threonine kinase mechanistic target of rapamycin (mTOR) plays a pivotal role in the regulation of cell proliferation, survival, and motility in response to availability of energy and nutrients as well as mitogens. The mTOR signaling axis regulates important biological processes, including cellular growth, metabolism, and survival in many tissues. In the skin, dysregulation of PI3K/AKT/mTOR pathway may lead to severe pathological conditions characterized by uncontrolled proliferation and inflammation, including skin hyperproliferative as well as malignant diseases. Herein, we provide an update on the current knowledge regarding the pathogenic implication of the mTOR pathway in skin diseases with inflammatory features (such as psoriasis, atopic dermatitis, pemphigus, and acne) and malignant characteristics (such as cutaneous T cell lymphoma and melanoma) while we critically discuss current and future perspectives for therapeutic targeting of mTOR axis in clinical practice.

Expression and significance of mammalian target of rapamycin in cutaneous squamous cell carcinoma and precancerous lesions

The aim of this study is to explore the role of mammalian target of rapamycin (mTOR) in cutaneous squamous cell carcinoma (CSCC), Bowen’s disease (BD), and actinic keratosis (AK) with squamous cell differentiation abnormality and its relationship with the degree of tumor proliferation. Thirty cases of clinical paraffin specimens of CSCC, BD, and AK were each collected from Jinhua Fifth Hospital, while 30 cases of normal skin specimens surgically resected in Department of Plastic Surgery were selected as controls. The expressions of mTOR and Ki-67 in tissues were detected by immunohistochemical staining. The positive expression rate of mTOR in the CSCC group was higher than those in the BD group and AK group (P < 0.05), while it was higher in the BD group and AK group than in the normal skin group (P < 0.05). The CSCC group had a higher positive expression rate of Ki-67 than the AK group (P < 0.01). The results of logistic regression analysis showed that the pathogenic site [odds ratio (OR) = 1.189, 95% confidence interval (95%CI): 1.028–1.381, P = 0.021], course of disease (OR = 2.059, 95%CI: 1.036–4.087, P = 0.043), and differentiation degree (OR = 1.325, 95%CI: 1.169–1.512, P = 0.001) were independent factors for the positive expression of mTOR. OR>1, indicating that the factor is a risk factor. The expression levels of mTOR in CSCC, BD, and AK were positively correlated with the expression level of Ki-67 (r = 0.827, P < 0.01, r = 0.608, P < 0.01, r = 0.368, P = 0.045). These results suggest that mTOR may be involved in the pathogenesis of CSCC, and related to the proliferation degree of CSCC, as an index reflecting the proliferation status of CSCC.

Koebner phenomenon leading to the formation of new psoriatic lesions: evidences and mechanisms

Koebner phenomenon refers to the emergence of new psoriatic lesions in the healthy skin regions following an injury/trauma to psoriatic patients. The occurrence of psoriatic lesions at unusual areas of the body regions such as on penis, around eyes and on keloids suggest that the Koebner phenomenon may be responsible for these lesions. A number of agents/triggers have been reported to induce the development of new psoriatic lesions in healthy skin areas and these include, tattooing skin, radiations, skin incision, viral infections and striae etc. The different mechanisms that contribute in inducing the development of new psoriatic lesions as Koebernization include the involvement of mast cell-derived inflammatory mediators such as tryptase, IL-6, IL-8, IL-17, and IL-36γ. Moreover, an increased expression of nerve growth factor (NGF) and vascular endothelial growth factor (VEGF) also contribute in Koebernization. Apart from these, there is a critical role of α 2 β1 integrins, S100A7 (psoriasin) and S100A15 (koebnerisin), change in the ratio of CD4+/CD8+ T cells, down-regulation of mechanosensitive polycystin 1 protein, decrease in inflammation controlling atypical chemokine receptor 2 (ACKR2), reduced expression of N-methyl-d-aspartate (NMDA) receptors (NMDARs) on the keratinocytes and increase in levels of chemokines (CXCL8 and CCL20) in inducing formation of new psoriatic lesions. The present review discusses the role of Koebner phenomenon in the development of new psoriatic lesions. Moreover, it also describes the mechanisms involved in Koebernization in the form of discussion of different key targets that may be potentially modulated pharmacologically to attenuate/halt the development of new psoriatic lesions.

Polycystin-1 induces activation of the PI3K/AKT/mTOR pathway and promotes angiogenesis in renal cell carcinoma

In the present study we investigated the expression and the functional role of mechanosensitive polycystins in renal cell carcinoma (RCC). In 115 RCC patients we evaluated the protein expression of polycystin-1 (PC1), polycystin-2 (PC2), VEGF and protein components of the PI3K/Akt/mTOR pathway, which have been implicated both in RCC and polycystic kidney disease. PC1 and PC2 demonstrated reduced expression throughout the RCC tissue compared to the adjacent normal tissue. PC1 and PC2 revealed high expression when they were associated with higher grade and decreased 5-year survival respectively. PC1 and PC2 were positively correlated with p110γ subunit of PI3K and high PC1 expressing cells tended to display activation/phosphorylation of Akt. There was also a positive association between PC1 and VEGF expression, whereas PC1 augmented the tumor's microvascular network in stage IV carcinomas. In human RCC cells, functional inhibition of PC1 resulted in upregulation of the PI3K/Akt/mTOR pathway, enhanced cell proliferation and led to inhibition of cell migration. Conclusively, aberrant PC1 regulation is associated with increased angiogenesis and features of advanced disease in RCC tissues.

Sudachitin, a polymethoxyflavone from Citrus sudachi, induces apoptosis via the regulation of MAPK pathways in human keratinocyte HaCaT cells

Although we recently reported that sudachitin (5,7,4'-trihydroxy-6,8,3'-trimethoxyflavone), a polymethoxyflavone isolated from the peel of Citrus sudachi, can induce apoptosis in human keratinocyte HaCaT cells, the mechanism underlying its action remains unclear. In this study, we explored the mechanisms underlying sudachitin-induced apoptosis in HaCaT cells. Sudachitin activated p38MAPK and inhibited ERK1/2, whereas another polymethoxyflavone, nobiletin (5,6,7,8,3',4'-hexamethoxyflavone), activated ERK1/2. The p38MAPK inhibitor SB203580 significantly attenuated sudachitin-induced heat shock protein 27 phosphorylation, downstream of p38MAPK, and subsequent apoptosis, indicating that sudachitin induces apoptosis via the p38MAPK pathway. Additionally, sudachitin inhibited serum- and EGF-stimulated Raf-1-ERK1/2 activation, and blocked EGF-induced cell migration and proliferation in HaCaT cells. These results suggest that small structural differences in polymethoxyflavones can induce different cellular responses by altering the regulation of MAPK activities and that sudachitin may be a potential candidate for developing new drugs for skin diseases such as psoriasis.

Polycystins and Mechanotransduction in Human Disease

Alterations in the process of mechanotransduction have been implicated in the pathogenesis of several diseases such as genetic diseases, osteoporosis, cardiovascular anomalies, and cancer. Several studies over the past twenty years have demonstrated that polycystins (polycystin-1, PC1; and polycystin-2, PC2) respond to changes of extracellular mechanical cues, and mediate pathogenic mechanotransduction and cyst formation in kidney cells. However, recent reports reveal the emergence of polycystins as key proteins that facilitate the transduction of mechano-induced signals in various clinical entities besides polycystic kidney disease, such as cancer, cardiovascular defects, bone loss, and deformations, as well as inflammatory processes like psoriasis. Herewith, we discuss data from recent studies that establish this role with potential clinical utility.

Polycystins in disease mechanobiology

Distorted mechanotransduction represents the molecular hallmark of disease mechanobiology and is displayed with common features during the development of various pathophysiologies. Polycystins constitute a family of mechanosensitive proteins that facilitate pathogenic signal transduction mechanisms. The main representatives of the family are polycystin-1 (PC1) and polycystin-2 (PC2), which function as a mechano-induced membrane receptor and a calcium-permeable ion channel, respectively. PC1 and PC2 mediate extracellular mechanical stimulation, induce intracellular molecular signaling and evoke corresponding gene transcription. Recent reports reveal that polycystin-mediated signaling does not occur in polycystic kidney disease only, where it is most prominently studied. It is also present during the development of clinical entities such as endothelial dysfunction and atheromatosis, deregulation of osteoblast differentiation, cancer development, and psoriasis. In this study, we highlight emerging data that support the overall contribution of polycystins to disease mechanobiology and suggest further exploration of this protein family in diseases generated from force-bearing tissue structures.

Epidermal mTORC1 Signaling Contributes to the Pathogenesis of Psoriasis and Could Serve as a Therapeutic Target

Although modern biologics targeting different inflammatory mediators show promising therapeutic success, comprehensive knowledge about the molecular events in psoriatic keratinocytes that contribute to the pathogenesis and could serve as therapeutic targets is still scarce. However, recent efforts to understand the deregulated signal transduction pathways have led to the development of small molecule inhibitors e.g., tofacitinib targeting the Jak/Stat cascade that opens additional therapeutic options. Recently, the PI3-K/Akt/mTOR signaling pathway has emerged as an important player in the control of epidermal homeostasis. This review summarizes the current knowledge on the role of this pathway in the pathogenesis of psoriasis, especially the epidermal manifestation of the disease and discusses current approaches to target the pathway therapeutically.