The mechanism of submandibular gland dysfunction after menopause may be associated with the ferroptosis

Ferroptosis in organ fibrosis: From mechanisms to therapeutic medicines

Fibrosis occurs in many organs, and its sustained progress can lead to organ destruction and malfunction. Although numerous studies on organ fibrosis have been carried out, its underlying mechanism is largely unknown, and no ideal treatment is currently available. Ferroptosis is an iron-dependent process of programmed cell death that is characterized by lipid peroxidation. In the past decade, a growing body of evidence demonstrated the association between ferroptosis and fibrotic diseases, while targeting ferroptosis may serve as a potential therapeutic strategy. This review highlights recent advances in the crosstalk between ferroptosis and organ fibrosis, and discusses ferroptosis-targeted therapeutic approaches against fibrosis that are currently being explored.

Dental Pulp Stem Cells for Salivary Gland Regeneration-Where Are We Today?

Xerostomia is the phenomenon of dry mouth and is mostly caused by hypofunction of the salivary glands. This hypofunction can be caused by tumors, head and neck irradiation, hormonal changes, inflammation or autoimmune disease such as Sjögren's syndrome. It is associated with a tremendous decrease in health-related quality of life due to impairment of articulation, ingestion and oral immune defenses. Current treatment concepts mainly consist of saliva substitutes and parasympathomimetic drugs, but the outcome of these therapies is deficient. Regenerative medicine is a promising approach for the treatment of compromised tissue. For this purpose, stem cells can be utilized due to their ability to differentiate into various cell types. Dental pulp stem cells are adult stem cells that can be easily harvested from extracted teeth. They can form tissues of all three germ layers and are therefore becoming more and more popular for tissue engineering. Another potential benefit of these cells is their immunomodulatory effect. They suppress proinflammatory pathways of lymphocytes and could therefore probably be used for the treatment of chronic inflammation and autoimmune disease. These attributes make dental pulp stem cells an interesting tool for the regeneration of salivary glands and the treatment of xerostomia. Nevertheless, clinical studies are still missing. This review will highlight the current strategies for using dental pulp stem cells in the regeneration of salivary gland tissue.

Effect of deferoxamine and ferrostatin-1 on salivary gland dysfunction in ovariectomized rats

The mechanism underlying xerostomia after menopause has not yet been fully elucidated. This study aimed to investigate the mechanism of xerostomia and the effect of the ferroptosis inhibitors deferoxamine (DFO) and ferrostatin-1 (FER) on salivary gland dysfunction in a postmenopausal animal model. Twenty-four female Sprague-Dawley rats were randomly divided into four groups: a SHAM group (n = 6, sham-operated rats), an OVX group (n = 6, ovariectomized rats), an FER group (n = 6, ovariectomized rats injected intraperitoneally with FER), and a DFO group (n = 6, ovariectomized rats injected intraperitoneally with DFO). GPX4 activity, iron accumulation, lipid peroxidation, inflammation, fibrosis, and salivary gland function were analyzed. Recovery of GPX4 activity and a decrease in iron accumulation and cytosolic MDA + HAE were observed in the DFO group. In addition, collagen I, collagen III, TGF-β, IL-6, TNF-α, and TGF-β levels were decreased in the DFO group compared to the OVX group. Recovery of GPX4 activity and the morphology of mitochondria, and reduction of cytosolic MDA + HAE were also observed in the FER group. In addition, decreased expression of inflammatory cytokines and fibrosis markers and increased expression of AQP5 were observed in both the DFO and FER groups. Postmenopausal salivary gland dysfunction is associated with ferroptosis, and DFO and FER may reverse the postmenopausal salivary gland dysfunction after menopause. DFO and FER are hence considered promising treatments for postmenopausal xerostomia.

Adiponectin is associated with inflammaging and age-related salivary gland lipid accumulation

Dry mouth is frequently observed in the elderly, and enhanced lipid accumulation plays a critical role in cellular senescence in the salivary gland (SG). We investigated the mechanisms that mediate lipogenesis-associated SG senescence. Adult (28.6 ± 6.6 y.o. and 43.3 ± 1.5 y.o.) and aged (82.0 ± 4.3 y.o. and 88.0 ± 4.3 y.o.) human parotid and submandibular glands were compared with respect to histologic findings, 8-OHdG (8-hydroxy 2 deoxyguanosine) expression patterns, TUNEL (Terminal deoxynucleotidyl transferase dUTP nick end labeling) and SA-β-gal (senescence-associated β-galactosidase) assay results. Also, microarray analysis was performed on RNA extracted from adult and aged SG to identify DEGs (differentially expressed genes). The effects of silencing ADIPOQ (Adiponectin) were evaluated by quantifying cell proliferation, immunohistochemical staining for cellular senescence and inflammation-associated proteins, SA-β-gal assays, RT-PCR, and western blot. Histological findings demonstrated the presence of more lipocytes, chronic inflammation, fibrosis, and lymphocytic infiltration in old SG. In addition, old tissues demonstrated higher expressions of SA-β-gal, more apoptotic cells in TUNEL assays, and higher oxidative stress by 8-OHdG immunostaining. Microarray analysis showed lipogenesis was significantly upregulated in old tissues. Silencing of ADIPOQ (a lipogenesis-related gene) reduced inflammation and SA-β-gal levels and increased cell proliferation and the expressions of amylase and aquaporin 5 in human SG epithelial cells. The study shows ADIPOQ is a potential target molecule for the modulation of lipogenesis associated with SG senescence.

Extracellular histone H3 facilitates ferroptosis in sepsis through ROS/JNK pathway

INTRODUCTION

Previous evidence realized the critical role of histone in disease control. The anti-inflammatory function of estradiol (E2) in sepsis has been documented. We here intended to unveil the role of extracellular histone H3 in sepsis regarding cell ferroptosis and the role of E2 in a such mechanism.

METHODS

Clinical sample, cecal ligation and puncture (CLP)-induced animal models and lipopolysaccharides (LPS)-induced cell models were prepared for testing relative expression of extracellular histone H3 and E2 as well as analyzing the role of extracellular histone H3 and E2 in sepsis concerning cell viability, reactive oxygen species (ROS), and ferroptosis.

RESULTS

Under sepsis, we found increased ferroptosis and extracellular histone H3 content, but reduced E2 concentration. Extracellular histone H3 facilitated ferroptosis of human umbilical vein endothelial cells (HUVECs) induced by LPS through activating the ROS/c-Jun N-terminal kinase (JNK) pathway. Moreover, E2 antagonized the effect of extracellular histone H3 on LPS-induced HUVEC ferroptosis and sepsis injury in CLP-induced animal models.

CONCLUSION

We highlighted that extracellular histone H3 facilitated lipopolysaccharides-induced HUVEC ferroptosis via activating ROS/JNK pathway, and such an effect could be antagonized by E2.

Effect of Echinochrome A on Submandibular Gland Dysfunction in Ovariectomized Rats

Post-menopausal dry mouth or xerostomia is caused by reduced salivary secretion. This study aimed to investigate the efficacy of echinochrome A (Ech A) in alleviating submandibular gland dysfunctions in ovariectomized rats that mimic menopause. Female rats that were eight-weeks-old were randomly divided into SHAM-6, -12; OVX-6, -12; and ECH-6, -12 groups (consisting of 6- and 12-weeks post-sham-operated, ovariectomized, and Ech A-treated ovariectomized rats, respectively). The ECH groups had lower body weight than OVX but similar food intake and estradiol or estrogen receptor β expression. However, the ECH groups had lower mRNA expression of sterol-regulatory element binding protein-1c (Srebp-1c), acetyl-CoA carboxylase (Acc), fatty acid synthase (Fasn), cluster of differentiation 36 (Cd36), and lipid vacuole deposition than OVX mice. Moreover, reactive oxygen species (ROS), malondialdehyde (MDA), and iron accumulation were lower in the ECH than in the OVX groups. Fibrosis markers, transforming growth factor β (Tgf-βI and Tgf-βII mRNA) increased in the OVX than SHAM groups but decreased in the ECH groups. Aquaporin (Aqp-1 and Aqp-5 mRNA) and mucin expressions were downregulated in the OVX groups but improved with Ech A. In addition, Ech A prevented post-menopausal salivary gland dysfunction by inhibiting lipogenesis and ferroptosis. These findings suggest Ech A as an effective remedy for treating menopausal dry mouth.

Physiological Effects of Ferroptosis on Organ Fibrosis

Ferroptosis is a new type of programmed cell death with unique morphological, biochemical, and genetic features. From the initial study of histomorphology to the exploration of subcellular organelles and even molecular mechanisms, a net connecting ferroptosis and fibrosis is being woven and formed. Inflammation may be the bridge between both processes. In this review, we will discuss the ferroptosis theory and process and the physiological functions of ferroptosis, followed by a description of the pathological effects and the underlying mechanisms of ferroptosis in the pathogenesis of tumorigenesis, ischemic damage, degenerative lesions, autoimmune diseases, and necroinflammation. We then focus on the role of ferroptosis in the fibrosis process in the liver, lung, kidney, heart, and other organs. Although the molecular mechanism of ferroptosis has been explored extensively in the past few years, many challenges remain to be resolved to translate this information into antifibrotic practice, which is becoming a promising new direction in the field of fibrotic disease prevention and treatment.

Resveratrol alleviates salivary gland dysfunction induced by ovariectomy in rats

Resveratrol (Res), found abundant in many medicinal plants, exerts multiple biological functions in the body, including anti-inflammatory, antioxidant, and anti-aging properties. Xerostomia is a major symptom of salivary gland dysfunction in menopausal women, which significantly compromises the quality of life. Here, we investigated the effect of Res on estrogen deficiency-induced salivary gland dysfunction in rats. We found that Res administration could reduce body weight and water consumption, and increase salivary fluid secretion and blood flow of the submandibular gland. Furthermore, Res therapy alleviated histological lesions, increased AQP5 expression, and inhibited cell apoptosis in submandibular gland tissue. Meanwhile, the action of antioxidants was restored and the levels of inflammatory cytokines were attenuated by Res supplementation. Collectively, Res effectively improved estrogen deficiency-induced hyposalivation, which may provide a novel, safe, and practical approach to protect the salivary glands of estrogen-deficient females against xerostomia.

ACE2 and TMPRSS2 Immunolocalization and COVID-19-Related Thyroid Disorder

Thyroid dysfunction has been reported to be an extrapulmonary symptom of COVID-19. It is important to identify the tissue subset that expresses angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2), which are essential for host infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in order to understand the viral pathogenesis of COVID-19-related thyroid dysfunction. We investigated the expression and distribution of ACE2- and TMPRSS2-expressing cells in the thyroid gland. RT-PCR and Western blotting were performed on human thyroid follicular cells (Nthy-ori3-1) and rat thyroid tissues to detect the expression levels of ACE and TMPRSS2 mRNA and proteins. We also analyzed the expression patterns of ACE2 and TMPRSS2 in 9 Sprague-Dawley rats and 15 human thyroid tissues, including 5 normal, 5 with Hashimoto's thyroiditis, and 5 with Graves' disease, by immunohistochemistry (IHC) and immunofluorescence. Both ACE2 and TMPRSS2 mRNAs and proteins were detected in the thyroid tissue. However, ACE2 and TMPRSS2 proteins were not expressed in thyroid follicular cells. In IHC, ACE2 and TMPRSS2 were not stained in the follicular cells. No cells co-expressed ACE2 and TMPRSS2. ACE2 was expressed in pericytes between follicles, and TMPRSS2 was mainly stained in the colloid inside the follicle. There was no difference in expression between the normal thyroid, Hashimoto's thyroiditis, and Graves' disease. SARS-CoV-2 does not directly invade the thyroid follicular cells. Whether SARS-CoV-2 infection of pericytes can affect COVID-19-related thyroid dysfunction warrants further study.

RNA-seq coupling two different methods of castration reveals new insights into androgen deficiency-caused degeneration of submaxillary gland in male Sprague Dawley rats

Background

Salivary gland (SMG) degeneration and dysfunction are common symptoms that occur after sex hormone deprivation, but the underlying mechanisms remain largely unknown. Additionally, immunocastration, which causes drop of sex hormones, has been developed as an alternative to surgical castration, however whether it exerts similar effects as surgical castration on the salivary glands is unknown. Through histological and RNA-seq analysis, we assessed changes in morphology and transcriptome of SMG in response to immunocastration (IM) versus surgical castration (bilateral orchiectomy, ORC).

Results

Compared to entire males (EM), ORC caused severe degeneration of SMG in rats, as evidenced by both decreased (P < 0.01) SMG weight and organ index, and by decreased (P < 0.01) quantity of SMG acini and ducts. IM had minimal effects (P > 0.05) on SMG weight and organ index, but it still caused degeneration (P < 0.05) of the acini and ducts. Even though, the quantity of both SMG acini and ducts was much higher (P < 0.001) in IM than in ORC. Functional enrichment analysis of the common regulated genes by ORC/IM revealed disrupted epithelial cell development, angiogenesis, anatomical structure morphogenesis and enhanced cell death are associated with SMG degeneration in deprivation of androgens. Integrated data analysis shown that there existed a selective hyperfunction of SMG ribosome and mitochondrion in ORC but not in IM, which might be associated with more severe degeneration of SMG in ORC than in IM.

Conclusions

Our findings suggested that both surgical castration and immunocastration caused SMG degeneration by disrupting epithelial cell development, angiogenesis, anatomical structure morphogenesis and enhancing cell death. But, surgical castration selectively induced hyperfunction of SMG ribosome and mitochondrion, thus causing more severe degeneration of SMG than immunocastration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08521-9.

Tonsil mesenchymal stem cells-derived extracellular vesicles prevent submandibular gland dysfunction in ovariectomized rats

Dry mouth that occurs after menopause significantly reduces the quality of life of the elderly. The extracellular vesicles derived from mesenchymal stem cells are being studied for application in various pathological conditions in the field of tissue regenerative medicine. This study is to investigate the therapeutic effect on salivary gland dysfunction occurring after ovariectomy using tonsil mesenchymal stem cells (T-MSCs)-derived extracellular vesicles. The rats were divided into the following groups: sham-operated rats (SHAM), rats that underwent ovariectomy (OVX), and rats that underwent OVX surgery and were simultaneously injected with T-MSC-derived extracellular vesicles (OVX+EV). The rats were sacrificed 6 weeks after ovariectomy. Estradiol levels decreased in the OVX group compared with those in the SHAM group. Extracellular vesicles had no effect on estradiol levels or estrogen receptor β expression. The evaluation of pro-inflammatory cytokines, TNF-α and IL-6, increased in the OVX group and decreased in the OVX+EV group. The expressions of collagen I and TGFβI increased in the OVX group but decreased in the OVX+EV group. Moreover, to examine submandibular gland function, AQP5 and α-amylase expressions were downregulated in the OVX group, but improved upon exosome injection. In conclusion, T-MSC-derived extracellular vesicles are useful for the prevented submandibular gland dysfunction that occurs after menopause.

Effects of oligonol on the submandibular gland in ovariectomized rats

The aim of this study was to observe the effects of oligonol on submandibular gland dysfunction in ovariectomized rats. We randomly divided female Sprague-Dawley rats into sham-operated, ovariectomized, and oligonol-treated ovariectomized groups. Oligonol was intraperitoneally administered at 30 mg/kg daily for six weeks. Lipogenesis increased after the ovariectomy while fatty acid oxidation increased and intracellular triglyceride levels decreased in response to oligonol treatment. Submandibular gland fibrosis characterized by collagen type I accumulation was observed in the ovariectomized group. However, oligonol markedly reduced fibrosis to a level comparable to that observed in the sham group. Aquaporin 1 and glucose transporter 4 were downregulated in the ovariectomized group. Nevertheless, both factors were significantly upregulated by oligonol treatment. However, aquaporin 5 was significantly downregulated in the oligonol treatment group. Our findings indicate that oligonol protects against damage in postmenopausal rat salivary glands.