Metformin improves salivary gland inflammation and hypofunction in murine Sjögren's syndrome

Agmatine alleviates diabetic-induced hyposalivation in rats: A histological and biochemical study

Diabetic patients commonly experience hyposalivation, which can cause challenges with eating, swallowing, dry mouth, and speaking. It also raises the likelihood of developing periodontal disease. This study aimed to evaluate if agmatine could improve the rate of salivation in rats with hyposalivation induced by streptozotocin (STZ). Five groups of Wistar rats were utilized with 10 animals in each group. They were classified as follows; Negative control group (G1), agmatine (G2) group, and Nicotinamide (NA)-STZ (G3) group; received a single intraperitoneal dose of 65 mg/kg of STZ after NA injection. NA was administered to protect residual β cells and enhance their insulin secretion; NA-STZ + Metformin (G4) Metformin-treated diabetic group; at day 10 diabetic rats received 50mg/kg orally for 28 days, and NA-STZ + Agmatine (G5) at day 10 diabetic rats received a daily intraperitoneal dose of 300 mg/kg Agmatine for 28 days. The salivary flow rate was assessed weekly. Then, the animals were euthanized, both parotid (PG) and submandibular (SMG) salivary glands were dissected, and the following parameters were assessed; salivary glands' histopathology, aquaporin 5 (AQP5), caspase-3, E-cadherin expressions, inflammatory markers and finally, salivary glands' oxidative stress status. Agmatine has alleviated the salivary glands' dysfunction in STZ-induced diabetic rats. It normalized diabetes mellitus-associated salivary glands' abnormalities including histopathological abnormalities, decreased AQP5 and E-cadherin expressions, increased caspase-3 expression, and oxidative stress and inflammatory parameters. Agmatine alleviates diabetes mellitus-associated hyposalivation. It can promote PGs and SMGs function through its histological and AQP5 expression improvements.

Causal Relationship Between Sjögren's Syndrome and Gut Microbiota: A Two-Sample Mendelian Randomization Study

Background: Gut microbiota have been previously reported to be related to a variety of immune diseases. However, the causal connection between Sjögren's syndrome (SS) and gut microbiota has yet to be clarified. Methods: We employed a two-sample Mendelian randomization (MR) analysis to evaluate the causal connection between gut microbiota and SS, utilizing summary statistics from genome-wide association studies (GWASs) obtained from the MiBioGen and FinnGen consortia. The inverse variance weighted (IVW) approach represents the primary method of Mendelian randomization (MR) analysis. Sensitivity analysis was used to eliminate instrumental variables heterogeneity and horizontal pleiotropy. In addition, we performed an analysis using independent GWAS summary statistics for SS from the European Bioinformatics Institute (EBI) dataset for further verify our results. Results: IVW results demonstrated that the phylum Lentisphaerae (OR = 0.79, 95% CI: 0.63-0.99, p = 0.037), class Deltaproteobacteria (OR = 0.67, 95% CI: 0.47-0.96, p = 0.030), family Porphyromonadaceae (OR = 0.60, 95% CI: 0.38-0.94, p = 0.026), genus Eubacterium coprostanoligenes group (OR = 0.61, 95% CI: 0.4-0.93, p = 0.021), genus Blautia (OR = 0.62, 95% CI: 0.43-0.90, p = 0.012), genus Butyricicoccus (OR = 0.61, 95% CI: 0.42-0.90, p = 0.012), genus Escherichia.Shigella (OR = 0.7, 95% CI: 0.49-0.99, p = 0.045) and genus Subdoligranulum (OR = 0.61, 95% CI: 0.44-0.86, p = 0.005) exhibited protective effects on SS. Relevant heterogeneity of horizontal pleiotropy or instrumental variables was not detected. Furthermore, repeating our results with an independent cohort provided by the EBI dataset, only the genus Eubacterium coprostanoligenes group remained significantly associated with the protective effect on SS (OR = 0.41, 95% CI: 0.18-0.91, p = 0.029). Two-step MR analysis further revealed that genus Eubacterium coprostanoligenes group exerts its protective effect by reducing CXCL6 levels in SS (OR, 0.87; 95% CI = 0.76-0.99, p = 0.033). Conclusions: Our study using two-sample MR analysis identified a causal association between multiple genera and SS. A two-step MR result calculated that genus Eubacterium coprostanoligenes group mediated its protective effect by reducing CXCL6 levels in SS. However, the datasets available from the MiBioGen and FinnGen consortia do not provide sufficient information or comprehensive demographic data for subgroup analyses. Additional validation using various omics technologies is necessary to comprehend the development of SS in the intricate interplay between genes and the environment over a period of time.

Therapeutic JAK1 Inhibition Reverses Lupus Nephritis in a Mouse Model and Demonstrates Transcriptional Changes Consistent With Human Disease

OBJECTIVE

Janus kinase family members are essential for signaling by multiple cytokines, including many implicated in systemic lupus erythematosus (SLE) pathogenesis. To test whether inhibition of JAK1 signaling can be efficacious in SLE, we used a JAK1-selective inhibitor (ABT-317) and evaluated its ability to ameliorate disease in murine SLE.

METHODS

Efficacy of ABT-317 was evaluated using NZB/W-F1 mice treated prophylactically and therapeutically. Primary endpoints were proteinuria, survival, and saliva production. Other endpoints included histological analysis of kidneys and salivary glands, flow cytometric analysis of splenic cell populations, and gene expression analysis by RNA sequencing in the kidneys, salivary glands, and blood. Publicly available human kidney gene transcription data were used to assess the translatability of the mouse findings.

RESULTS

ABT-317 was efficacious when dosed prophylactically and prevented disease for up to two months after treatment cessation. When dosed therapeutically, ABT-317 quickly reversed severe proteinuria and restored saliva production, as well as diminished kidney and salivary gland inflammation. ABT-317-induced changes in glomerular morphology coincided with normalization of a human nephrotic gene signature, suggesting translatability to human lupus nephritis (LN).

CONCLUSION

JAK1 inhibition prevented and reversed kidney and salivary gland manifestations of murine lupus with long-lasting effects after treatment cessation. These data, along with the presence of JAK1 and nephrotic gene signatures in human LN glomeruli, suggest that a JAK1-selective inhibitor may be an effective therapeutic in the treatment of human SLE and LN.

Metformin-mediated effects on mesenchymal stem cells and mechanisms: proliferation, differentiation and aging

Mesenchymal stem cells (MSCs) are a type of pluripotent adult stem cell with strong self-renewal and multi-differentiation abilities. Their excellent biological traits, minimal immunogenicity, and abundant availability have made them the perfect seed cells for treating a wide range of diseases. After more than 60 years of clinical practice, metformin is currently one of the most commonly used hypoglycaemic drugs for type 2 diabetes in clinical practice. In addition, metformin has shown great potential in the treatment of various systemic diseases except for type 2 diabetes in recent years, and the mechanisms are involved with antioxidant stress, anti-inflammatory, and induced autophagy, etc. This article reviews the effects and the underlying mechanisms of metformin on the biological properties, including proliferation, multi-differentiation, and aging, of MSCs in vitro and in vivo with the aim of providing theoretical support for in-depth scientific research and clinical applications in MSCs-mediated disease treatment.

Dissecting the Roles of the Nuclear and Mitochondrial Genomes in a Mouse Model of Autoimmune Diabetes

Mitochondria, the organelles responsible for generating ATP in eukaryotic cells, have been previously implicated as a contributor to diabetes. However, mitochondrial proteins are encoded by both nuclear DNA (nDNA) and mtDNA. In order to better understand the relative contribution of each of these genomes to diabetes, a chimeric mitochondrial-nuclear exchange (MNX) mouse was created via pronuclear transfer carrying nDNA from a strain susceptible to type 1 diabetes (NOD/ShiLtJ) and mtDNA from nondiabetic C57BL/6J mice. Inheritance of the resulting heteroplasmic mtDNA mixture was then tracked across multiple generations, showing that offspring heteroplasmy generally followed that of the mother, with occasional large shifts consistent with an mtDNA bottleneck in the germ line. In addition, survival and incidence of diabetes in MNX mice were tracked and compared with those in unaltered NOD/ShiLtJ control mice. The results indicated improved survival and a delay in diabetes onset in the MNX mice, demonstrating that mtDNA has a critical influence on disease phenotype. Finally, enzyme activity assays showed that the NOD/ShiLtJ mice had significant hyperactivity of complex I of the electron transport chain relative to MNX mice, suggesting that a particular mtDNA variant (m.9461T>C) may be responsible for disease causation in the original NOD/ShiLtJ strain.

ARTICLE HIGHLIGHTS

Mitochondria have been previously implicated in diabetes, but the specific genetic factors remain unclear. To better understand the contributions of mitochondrial genes in nuclear DNA (nDNA) versus mtDNA, we created mitochondrial-nuclear exchange (MNX) mice carrying nDNA from a diabetic strain and mtDNA from nondiabetic mice. Long-term tracking of MNX mice showed occasional large shifts in heteroplasmy consistent with an mtDNA bottleneck in the germ line. In addition, the MNX mice showed improved survival and delayed incidence of diabetes relative to the unaltered diabetic mice, which appeared to be linked to the activity of respiratory complex I.

Effect of acupuncture on regulating IL-17, TNF-ɑ and AQPs in Sjögren's syndrome

AIM

The aim of the study was to observe the effect of acupuncture on regulating interleukin (IL)-17, tumor necrosis factor (TNF)-ɑ, and aquaporins (AQPs) in Sjögren's syndrome (SS) on patients and on non-obese diabetic (NOD) models.

METHODS

Levels of anti-AQP 1, 5, 8, and 9 antibodies, IL-17, and TNF-ɑ in the serum of SS patients were compared prior and following 20 acupuncture treatment visits during 8 weeks. While in murine model, five groups were divided to receive interventions for 4 weeks, including control, model, acupuncture, isoflurane, and hydroxychloroquine. The submaxillofacial gland index, histology, immunohistochemistry of AQP1, 5, salivary flow, together with IL-17, and TNF-ɑ expression in peripheral blood were compared among the groups.

RESULTS

Acupuncture reduced IL-17, TNF-ɑ, and immunoglobin A levels, and numeric analog scale of dryness in 14 patients with SS (p < 0.05). The salivary flow was increased, and the water intake decreased in NOD mice receiving acupuncture treatments. IL-17 and TNF-ɑ levels in peripheral serum were down-regulated (p < 0.05) and AQP1, 5 expression in the submandibular glands up-regulated in mice.

CONCLUSION

The effect on relieving xerostomia with acupuncture may be achieved by up-regulating the expression of AQP1. AQP5, down-regulating levels of IL-17 and TNF-ɑ, and a decrease in inflammation of glands.

Metformin-induced activation of Ca2+ signaling prevents immune infiltration/pathology in Sjogren's syndrome-prone mouse models

Immune cell infiltration and glandular dysfunction are the hallmarks of autoimmune diseases such as primary Sjogren's syndrome (pSS), however, the mechanism(s) is unknown. Our data show that metformin-treatment induces Ca2+ signaling that restores saliva secretion and prevents immune cell infiltration in the salivary glands of IL14α-transgenic mice (IL14α), which is a model for pSS. Mechanistically, we show that loss of Ca2+ signaling is a major contributing factor, which is restored by metformin treatment, in IL14α mice. Furthermore, the loss of Ca2+ signaling leads to ER stress in salivary glands. Finally, restoration of metformin-induced Ca2+ signaling inhibited the release of alarmins and prevented the activation of ER stress that was essential for immune cell infiltration. These results suggest that loss of metformin-mediated activation of Ca2+ signaling prevents ER stress, which inhibited the release of alarmins that induces immune cell infiltration leading to salivary gland dysfunction observed in pSS.

The Role and Mechanism of Metformin in Inflammatory Diseases

Metformin is a classical drug used to treat type 2 diabetes. With the development of research on metformin, it has been found that metformin also has several advantages aside from its hypoglycemic effect, such as anti-inflammatory, anti-aging, anti-cancer, improving intestinal flora, and other effects. The prevention of inflammation is critical because chronic inflammation is associated with numerous diseases of considerable public health. Therefore, there has been growing interest in the role of metformin in treating various inflammatory conditions. However, the precise anti-inflammatory mechanisms of metformin were inconsistent in the reported studies. Thus, this review aims to summarize various currently known possible mechanisms of metformin involved in inflammatory diseases and provide references for the clinical application of metformin.

Metformin Attenuates TGF-β1-Induced Fibrosis in Salivary Gland: A Preliminary Study

Fibrosis commonly arises from salivary gland injuries induced by factors such as inflammation, ductal obstruction, radiation, aging, and autoimmunity, leading to glandular atrophy and functional impairment. However, effective treatments for these injuries remain elusive. Transforming growth factor-beta 1 (TGF-β1) is fundamental in fibrosis, advancing fibroblast differentiation into myofibroblasts and enhancing the extracellular matrix in the salivary gland. The involvement of the SMAD pathway and reactive oxygen species (ROS) in this context has been postulated. Metformin, a type 2 diabetes mellitus (T2DM) medication, has been noted for its potent anti-fibrotic effects. Through human samples, primary salivary gland fibroblasts, and a rat model, this study explored metformin's anti-fibrotic properties. Elevated levels of TGF-β1 (p < 0.01) and alpha-smooth muscle actin (α-SMA) (p < 0.01) were observed in human sialadenitis samples. The analysis showed that metformin attenuates TGF-β1-induced fibrosis by inhibiting SMAD phosphorylation (p < 0.01) through adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)-independent pathways and activating the AMPK pathway, consequently suppressing NADPH oxidase 4 (NOX4) (p < 0.01), a main ROS producer. Moreover, in rats, metformin not only reduced glandular fibrosis post-ductal ligation but also protected acinar cells from ligation-induced injuries, thereby normalizing the levels of aquaporin 5 (AQP5) (p < 0.05). Overall, this study underscores the potential of metformin as a promising therapeutic option for salivary gland fibrosis.

Metformin mitigates radiation toxicity exerting antioxidant and genoprotective properties

The antidiabetic drug metformin (MF) exhibits redox-modulating effects in various pathologies associated with oxidative stress and mitigates ionizing radiation-induced toxicity, but the underlying mechanisms remain to be elucidated. Thus, we studied some radiomitigatory effects of MF and explored the possible mechanisms behind them. Highly sensitive luminescence methods and non-competitive enzyme-linked immunosorbent assay (ELISA) were used in in vitro studies, and in vivo the damage to bone marrow cells and its repair were assessed by the micronucleus test. In a solution, MF at concentrations exceeding 0.1 µM effectively intercepts •OH upon X-ray-irradiation, but does not react directly with H2O2. MF accelerates the decomposition of H2O2 catalyzed by copper ions. MF does not affect the radiation-induced formation of H2O2 in the solution of bovine gamma-globulin (BGG), but has a modulating effect on the generation of H2O2 in the solution of bovine serum albumin (BSA). MF at 0.05-1 mM decreases the radiation-induced formation of 8-oxoguanine in a DNA solution depending on the concentration of MF with a maximum at 0.25 mM. MF at doses of 3 mg/kg body weight (bw) and 30 mg/kg bw administered to mice after irradiation, but not before irradiation, reduces the frequency of micronucleus formation in polychromatophilic erythrocytes of mouse red bone marrow. Our work has shown that the radiomitigatory properties of MF are mediated by antioxidant mechanisms of action, possibly including its ability to chelate polyvalent metal ions.

Mitochondrial Control for Healthy and Autoimmune T Cells

T cells are critical players in adaptive immunity, driving the tissue injury and organ damage of patients with autoimmune diseases. Consequently, investigations on T cell activation, differentiation, and function are valuable in uncovering the disease pathogenesis, thus exploring promising therapeutics for autoimmune diseases. In recent decades, accumulating studies have pinpointed immunometabolism as the fundamental determinant in controlling T cell fate. Specifically, mitochondria, as a hub of intracellular metabolism, connect glucose, lipid, and amino acid metabolic pathways. Herein, we summarize metabolic adaptations of mitochondrial oxidative phosphorylation and the relevant glucose, lipid, and amino acid metabolism during T cell activation, differentiation, and function. Further, we focused on current updates of the molecular bases for metabolic reprogramming in autoimmune T cells and advances in exploring metabolic-targeted therapeutics against autoimmune diseases. This might facilitate the in-depth understanding of autoimmune pathogeneses and the clinical management of autoimmune diseases.

AMPK Activation Restores Salivary Function Following Radiation Treatment

Head and neck cancers represent a significant portion of cancer diagnoses, with head and neck cancer incidence increasing in some parts of the world. Typical treatment of early-stage head and neck cancers includes either surgery or radiotherapy; however, advanced cases often require surgery followed by radiation and chemotherapy. Salivary gland damage following radiotherapy leads to severe and chronic hypofunction with decreased salivary output, xerostomia, impaired ability to chew and swallow, increased risk of developing oral mucositis, and malnutrition. There is currently no standard of care for radiation-induced salivary gland dysfunction, and treatment is often limited to palliative treatment that provides only temporary relief. Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is an enzyme that activates catabolic processes and has been shown to influence the cell cycle, proliferation, and autophagy. In the present study, we found that radiation (IR) treatment decreases tissue levels of phosphorylated AMPK following radiation and decreases intracellular NAD+ and AMP while increasing intracellular adenosine triphosphate. Furthermore, expression of sirtuin 1 (SIRT1) and nicotinamide phosphoribosyl transferase (NAMPT) was lower 5 d following IR. Treatment with AMPK activators, 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) and metformin, attenuated compensatory proliferation (days 6, 7, and 30) following IR and reversed chronic (day 30) salivary gland dysfunction post-IR. In addition, treatment with metformin or AICAR increased markers of apical/basolateral polarity (phosphorylated aPKCζT560-positive area) and differentiation (amylase-positive area) within irradiated parotid glands to levels similar to untreated controls. Taken together, these data suggest that AMPK may be a novel therapeutic target for treatment of radiation-induced salivary damage.

STAT3 as a therapeutic target in the metformin-related treatment

Signal transducers and activators of transcription 3 (STAT3) signaling plays an important role in mediating tumor progression, inflammation, cardiovascular disease, and other pathological processes.In recent years, STAT3 as a therapeutic target has received extensive attention. It is well known that metformin can play the role of hypoglycemia by activating AMP-activated protein kinase (AMPK) through inhibition of mitochondrial ATP production.However, AMPK is not required for metformin activity.Although the application of STAT3 as a therapeutic target of metformin is still in the initial research stage, the importance of STAT3 in the mechanism of metformin is gradually being recognizedand further studies are needed to demonstrate the important role of the STAT3 regulatory network in the regulation of diseases by metformin. Here, we reviewed in detail that metformin inhibits the progression of various diseases like tumors, autoimmune diseases and hormone-related diseases by regulating multiple signaling pathways such as JAK/STAT3 and mTOR/STAT3 signaling centered on STAT3. We also summarized recent advances of STAT3 inhibitors combined with metformin in the treatment of diseases.We emphasized that STAT3 signaling, as an AMPK-independent signaling pathway, may be an important target for metformin in clinical therapy.

Pathogenesis and treatment of Sjogren's syndrome: Review and update

Sjogren's syndrome (SS) is a chronic autoimmune disease accompanied by multiple lesions. The main manifestations include dryness of the mouth and eyes, along with systemic complications (e.g., pulmonary disease, kidney injury, and lymphoma). In this review, we highlight that IFNs, Th17 cell-related cytokines (IL-17 and IL-23), and B cell-related cytokines (TNF and BAFF) are crucial for the pathogenesis of SS. We also summarize the advances in experimental treatment strategies, including targeting Treg/Th17, mesenchymal stem cell treatment, targeting BAFF, inhibiting JAK pathway, et al. Similar to that of SLE, RA, and MS, biotherapeutic strategies of SS consist of neutralizing antibodies and inflammation-related receptor blockers targeting proinflammatory signaling pathways. However, clinical research on SS therapy is comparatively rare. Moreover, the differences in the curative effects of immunotherapies among SS and other autoimmune diseases are not fully understood. We emphasize that targeted drugs, low-side-effect drugs, and combination therapies should be the focus of future research.

Metformin and Its Immune-Mediated Effects in Various Diseases

Metformin has been a long-standing prescribed drug for treatment of type 2 diabetes (T2D) and its beneficial effects on virus infection, autoimmune diseases, aging and cancers are also recognized. Metformin modulates the differentiation and activation of various immune-mediated cells such as CD4+ and CD+8 T cells. The activation of adenosine 5'-monophosphate-activated protein kinase (AMPK) and mammalian target of rapamycin complex 1 (mTORC1) pathway may be involved in this process. Recent studies using Extracellular Flux Analyzer demonstrated that metformin alters the activities of glycolysis, oxidative phosphorylation (OXPHOS), lipid oxidation, and glutaminolysis, which tightly link to the modulation of cytokine production in CD4+ and CD+8 T cells in various disease states, such as virus infection, autoimmune diseases, aging and cancers.

Sex hormones, body mass index, and related comorbidities associated with developing Sjögren's disease: a nested case-control study

OBJECTIVE

Sjögren's disease (SjD), a highly female predominant systemic autoimmune disease, peaks in perimenopause. Prior studies lack details on timing or type of sex hormone exposure. We examined SjD risk using endogenous and exogenous hormone exposure and related comorbidities.

METHODS

We performed a retrospective case-control study of adult women, nested within a population cohort. Cases had SjD diagnosed by a rheumatology provider or two SjD diagnoses from a non-rheumatology provider with a positive anti-SSA antibody or salivary gland biopsy. Cases were age-matched to three SjD-free controls. We calculated modified composite estrogen scores (mCES) and collected demographics, comorbidities, and endogenous and exogenous hormone exposures. Risk ratios were adjusted for demographics.

RESULTS

Of 546 SjD cases and 1637 age-matched controls, mCES was not significantly associated with SjD in adjusted models. The top individual hormone exposures associated with SjD included estrogen replacement therapy (ERT; RR 1.78 [95% CI 1.47-2.14]), polycystic ovarian syndrome (1.65 [1.28-2.12]), and hysterectomy without bilateral oophorectomy (1.51 [1.13-2.03]). We identified comorbidities preceding SjD including fibromyalgia, pulmonary disease, diabetes, lymphoma, osteoporosis, peripheral vascular disease, and renal disease. Taking comorbidities into account, we developed a predictive model for SjD that included fibromyalgia (2.50 [1.93-3.25]), osteoporosis (1.84 [1.27-2.66]), hormone replacement therapy (HRT) (1.61 [1.22-2.12]), diabetes (0.27 [0.13-0.50]), and body mass index (BMI) (0.97 [0.95-0.99]).

CONCLUSIONS

We report a novel algorithm to improve identifying patients at risk for SjD and describe sex hormone association with SjD. Finally, we report new comorbidities associated with SjD decrease, BMI and diabetes, and increase, lymphoma and osteoporosis.. Key Points •Given female predominance and typical perimenopausal onset, sex hormones should be considered when studying comorbidities in Sjögren's disease. •The top exposures associated with developing Sjögren's disease included fibromyalgia, osteoporosis, and use of hormone replacement therapy. Possible protective factors included prior diabetes and higher body mass index. •We used our newly identified exposures to generate a predictive algorithm, which has potential to improve diagnosis and pathogenic insights into Sjögren's disease.

Ruscogenin Ameliorated Sjögren's Syndrome by Inhibiting NLRP3 Inflammasome Activation

This article investigated the role and the specific mechanism of Ruscogenin in Sjögren's syndrome (SS). NOD/ShiLtJ mice were treated with Ruscogenin, and acinar cells isolated from submandibular glands were treated with TNF-α, Ruscogenin and transfected with NLRP3 overexpression plasmid. Salivary flow rate (SFR) was measured at weeks 11, 13, 15, 17, and 20. Histological analysis of the submandibular glands was conducted by hematoxylin-eosin staining assay. IL-6, IL-17, TNF-α, and IL-1β mRNA expression was detected through qRT-PCR. AQP 5, AQP 4, P2X7R, NLRP3, caspase 1, IL-1β, Bax, and Bcl-2 protein levels were tested by western blot. Cell apoptosis was assessed through acridine orange and propidium iodide (AO/PI) staining assay and flow cytometry assay. Ruscogenin ameliorated the SFR and submandibular gland inflammation of NOD/ShiLtJ mice. Ruscogenin promoted the preservation of acinar cells and suppressed inflammation-related factors (P2X7R, NLRP3, caspase 1, and IL-1β) in submandibular gland tissues of NOD/ShiLtJ mice. Ruscogenin inhibited acinar cell apoptosis in NOD/ShiLtJ mice and reversed TNF-α-induced apoptosis and inflammation of acinar cells. NLRP3 overexpression reversed the repressive effect of Ruscogenin on TNF-α-induced inflammation and apoptosis of acinar cells. Ruscogenin ameliorated SS by inhibiting NLRP3 inflammasome activation.

Quercetin ameliorates salivary gland apoptosis and inflammation in primary Sjögren's syndrome through regulation of the leptin/OB-R signaling

Dry mouth is the main manifestation of Sjögren syndrome (SS). Quercetin has been reported to alleviate radiation-induced salivary gland damage, yet the effect of quercetin on SS-caused salivary gland damage remains unclear. This study aimed to investigate the effects of quercetin on SS-induced salivary gland damage and the mechanism underlying its therapeutic potential in SS. Here, NOD/Ltj mice were used to spontaneously mimic SS-induced salivary gland inflammation in vivo and salivary gland epithelial cells (SGECs) were stimulated by interferon-γ (IFN-γ) to mimic cell inflammation in vitro. Results showed that quercetin significantly reduced loss of saliva flow, salivary gland damage, cell apoptosis, and inflammatory response in NOD/Ltj mice. Quercetin treatment also significantly reduced the increased serum leptin (LP) levels in NOD/Ltj mice. Furthermore, quercetin blocked the increases in the expression of obesity receptor (OB-R) and its downstream Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signaling in the salivary glands. In vitro experiments confirmed that quercetin could protect SGECs from IFN-γ-induced cell apoptosis and inflammation through the LP/OB-R-activated JAK2/STAT3 signaling. Hence, quercetin might protect against SS-induced salivary gland damage by relieving cell apoptosis and inflammation by inhibiting the LP/OB-R signaling, providing a new perspective for treating SS-induced dry mouth.

Low Dose Interleukin-2 Ameliorates Sjögren's Syndrome in a Murine Model

Sjögren's syndrome (SS) is a systemic autoimmune disease with no efficient treatment, and it is associated with dysregulated immune cells and impaired interleukin (IL)-2 signaling. IL-2 is critical for the development and maintenance of Treg cells. The use of low dose of IL-2 (LDIL-2) in the treatment of autoimmune diseases is promising, but the efficacy and mechanism in SS therapy are still to be confirmed. This study aims to investigate the therapeutic effect of LDIL-2 on SS in NOD (non-obese diabetic) mice. NOD mice (female, 8 weeks old) were randomly assigned into three groups (n = 8). Low dose of IL-2 (LDIL-2), high dose of IL-2 (HDIL-2), and isometric sterile water (control) were administered subcutaneously daily from week 8 to week 16. LDIL-2 administration significantly recovered the reduction in saliva flow and suppressed lymphocyte inflammation of the submandibular glands (SMGs) when compared with those treated with sterile water as controls (p < 0.05). SS related biomarkers including ANA, Anti-SSA/Ro, and Anti-SSB/La also declined (p < 0.05). In the low dose of IL-2 treated group, the proportion of CD4+CD25+Foxp3+Tregs in both spleen and cervical-lymph-node were higher than control mice (p < 0.05). Furthermore, CD4+Bcl-6+PD-1+CXCR5+Tfh cells, CD4+IFN-γ+Th1 cells, and CD4+IL-17A+Th17 cells were significantly reduced in LDIL-2 group (p < 0.05). Analysis of the SMGs biopsies showed significantly decreased inflammation scores after LDIL-2 administration and an increase of Tregs with immunohistochemical staining. Our findings provide in vivo evidence that LDIL-2 was an effective therapeutic intervention for SS observed in NOD mice and may restore immune balance through the promotion of Treg and suppression of germinal center (GC) B cells and effector T cells.

Metformin protects 5-Fu-induced chemotherapy oral mucositis by reducing endoplasmic reticulum stress in mice

Metformin (Met) is a first-line and essential treatment for type 2 diabetes, with anti-inflammatory effects. It has been reported Met could inhibit NF-κB activity and down-regulate the release of inflammatory factors. However, whether Met has a protective effect on chemotherapy-induced oral mucositis(CIOM) is unknown. The purpose of this study was to evaluate the protective effect of Metformin(Met) on chemotherapy-induced oral mucositis(CIOM) and further explore its possible mechanism. 5-Fu was used in the C57BL/6 mice to establish the model of CIOM. Our results showed Met could significantly improve 5-Fu-induced mucosal damage, apoptosis, ROS and releasing of inflammatory factors in the tongue tissue. In addition, Met could inhibit 5-Fu-induced high expression of endoplasmic reticulum stress(ERS)-related proteins GRP78 and CHOP. Further studies showed that the protective effect of ERS inhibitor 4-PBA on CIOM was similar to Met. Moreover, Met inhibited the phosphorylation of NF-κB in tongue tissue, independent of AMPK phosphorylation. The protective effect of PDTC, an inhibitor of NF-κB, on tongue tissue was similar to that of Met. This study confirmed the protective effect of Met on 5-Fu-induced CIOM, which was achieved by inhibiting ERS and reducing the activity of NF-κB.

Redox Homeostasis Involvement in the Pharmacological Effects of Metformin in Systemic Lupus Erythematosus

Significance: Metformin has been proposed as a treatment for systemic lupus erythematosus (SLE). The primary target of metformin, the electron transport chain complex I in the mitochondria, is associated with redox homeostasis in immune cells, which plays a critical role in the pathogenesis of autoimmune diseases. This review addresses the evidence and knowledge gaps on whether a beneficial effect of metformin in lupus may be due to a restoration of a balanced redox state. Recent Advances: Clinical trials in SLE patients with mild-to-moderate disease activity and preclinical studies in mice have provided encouraging results for metformin. The mechanism by which this therapeutic effect was achieved is largely unknown. Metformin regulates redox homeostasis in a context-specific manner. Multiple cell types contribute to SLE, with evidence of increased mitochondrial oxidative stress in T cells and neutrophils. Critical Issues: The major knowledge gaps are whether the efficacy of metformin is linked to a restored redox homeostasis in the immune system, and if it does, in which cell types it occurs? We also need to know which patients may have a better response to metformin, and whether it corresponds to a specific mechanism? Finally, the identification of biomarkers to predict treatment outcomes would be of great value. Future Directions: Mechanistic studies must address the context-dependent pharmacological effects of metformin. Multiple cell types as well as a complex disease etiology should be considered. These studies must integrate the rapid advances made in understanding how metabolic programs direct the effector functions of immune cells. Antioxid. Redox Signal. 36, 462-479.

Pharmacological Inhibition of Glutaminase 1 Normalized the Metabolic State and CD4+ T Cell Response in Sjogren's Syndrome

Previous studies have shown that abnormal metabolic reprogramming in CD4+ T cells could explain the occurrence of several autoimmune disorders, including Sjogren's syndrome (SS). However, therapeutic targets of the abnormal metabolism of CD4+ T cells remain to be explored. Here, we report that glutaminase 1 (Gls1), a pivotal factor in glutaminolysis, might be involved in the pathogenesis of SS. The expression of Gls1 was upregulated in infiltrated labial CD4+ T cells and circulating CD4+ T cells of SS patients. Inhibiting Gls1 with BPTES significantly abolished the proliferation rate, as indicated by EdU, CFSE, and Western blot analyses. Additionally, BPTES downregulated the extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) values of activated CD4+ T cells from SS mice. In vivo, we injected different doses of BPTES into SS-like NOD/Ltj mice and found that 10 mg/kg BPTES significantly restored the salivary flow rate. Histological and qRT-PCR analyses showed that this concentration of BPTES attenuated lymphocytic infiltration and the numbers of PCNA-positive cells and CD4+ T cells. The proportions of IFNγ-producing cells and IL-17A-producing cells and the expression of several proinflammatory cytokines, including IFNγ and IL-17A, were also affected in the salivary glands of SS-like mice. Cytokine production in circulating serum was analyzed and showed that BPTES downregulated the effector functions of Th17 cells and Th1 cells. Collectively, these results indicate a positive relationship between Gls1 and SS development. Pharmacological inhibition of Gls1 with BPTES could normalize the effector functions of CD4+ T cells and effectively attenuate the symptoms of SS.

Metformin ameliorates chronic colitis in a mouse model by regulating interferon-γ-producing lamina propria CD4+ T cells through AMPK activation

Metformin, a commonly prescribed drug for type 2 diabetes mellitus, has been shown to activate AMP-activated protein kinase (AMPK). Notably, AMPK activation has recently been observed to be associated with anti-inflammatory responses. Metformin is also reported to elicit anti-inflammatory responses in CD4+ T cells, resulting in improvement in experimental chronic inflammatory diseases, such as systemic lupus erythematosus. To investigate the effect of metformin on inflammatory bowel disease (IBD), we developed a T cell-transfer model of chronic colitis in which SCID mice were injected with CD4+ CD45RBhigh T cells to induce colitis. We examined the effects of metformin via in vitro and in vivo experiments on lamina propria (LP) CD4+ T cells. We observed that metformin suppresses the frequency of interferon (IFN) -γ-producing LP CD4+ T cells in vitro, which were regulated by AMPK activation, a process possibly induced by the inhibition of oxidative phosphorylation. Furthermore, we examined the effects of metformin on an in vivo IBD model. Metformin-treated mice showed AMPK activation in LP CD4+ T cells and ameliorated colitis. Our study demonstrates that metformin-induced AMPK activation in mucosal CD4+ T cells contributes to the improvement of IBD by suppressing IFN-γ production. Moreover, our results indicate that AMPK may be a target molecule for the regulation of mucosal immunity and inflammation. Thus, AMPK-activating drugs such as metformin may be potential therapeutic agents for the treatment of IBD.

Metformin Use Was Associated With Reduced Risk of Incidental Sjögren's Syndrome in Patients With Type 2 Diabetes: A Population-Based Cohort Study

Purpose: Previous studies have shown that metformin exhibits an anti-inflammatory effect and may decrease the risk of incidental diabetes. But the effect of metformin on incidental Sjögren's syndrome is unknown. The aim of the study was to examine the association between metformin exposure and Sjögren's syndrome in diabetic patients. Methods: The dataset in this retrospective cohort study was obtained from the National Health Insurance Research Database (2000-2013) in Taiwan. In total, 15,098 type 2 diabetic patients under metformin treatment and an equivalent number without metformin treatment matched for comparison were included. The primary endpoint was the incidence of Sjogren's syndrome. Univariate and multivariate Cox proportional hazards models were used for data analysis. A subgroup analysis and sensitivity test were also performed. Results: The incidence rate of Sjögren's syndrome in non-metformin controls was 40.83 per 100,000 person-years and 16.82 per 100,000 person-years in metformin users. The adjusted hazard ratio (aHR) in diabetic patients under metformin treatment was 0.46 (95% CI, 0.23 to 0.92). In subgroup analysis, men had a lower risk of developing Sjögren's syndrome than women [aHR = 0.15, 95% CI = (0.05, 0.41)]. After prescribing metformin to type 2 diabetic patients aged 60 years or more, those patients had a lower risk of developing Sjögren's syndrome [aHR = 0.34, 95% CI = (0.12, 0.96)]. Conclusion: In this large population-based cohort study, metformin exposure was associated with a reduced risk of developing Sjögren's syndrome in type 2 diabetic patients.

Artesunate Combined With Metformin Ameliorate on Diabetes-Induced Xerostomia by Mitigating Superior Salivatory Nucleus and Salivary Glands Injury in Type 2 Diabetic Rats via the PI3K/AKT Pathway

Polydipsia and xerostomia are the most common complications that seriously affect oral health in patients with diabetes. However, to date, there is no effective treatment for diabetic xerostomia. Recent studies have reported that artesunate (ART) and metformin (Met) improve salivary gland (SG) hypofunction in murine Sjögren's syndrome. Therefore, aim of this study was to investigate the effect and underlying mechanism of artesunate (ART) alone and in combination with metformin (Met) on hyposalivation in type 2 diabetes mellitus (T2DM) rats. T2DM rats were induced using a high-fat diet and streptozotocin. SPF male Sprague-Dawley rats were divided into the following five groups: normal control group, untreated diabetic group, ART-treated diabetic group (50 mg/kg), Met-treated diabetic group (150 mg/kg), and ART/Met co-treated diabetic group (50 mg/kg ART and 150 mg/kg Met). ART and Met were intragastrically administered daily for 4 weeks. The general conditions, diabetes parameters and serum lipids were evaluated after drug treatment. Furthermore, we observed changes in the central superior salivatory nucleus (SSN) and SG, and changes in the AQP5 expression, parasympathetic innervation (AChE and BDNF expression), and PI3K/AKT pathway- (p-AKT, and p-PI3K), apoptosis- (Bax, Bcl-2, and Caspase3), and autophagy- (LC3 and P62) related markers expression in T2DM rats after treatment. Our results showed that ART or Met alone and ART/Met combination attenuated a range of diabetic symptoms, including weight loss, urine volume increase, water consumption increase, hyperglycemia, insulin resistance, glucose intolerance and dyslipidemia. More importantly, we found that these three treatments, especially ART/Met combination, mitigated hyposalivation in the T2DM rats via improving the central SSN and SGs damage in hyperglycemia. Our data also indicated that ART/Met attenuated SG damage though regulating the PI3K/Akt pathway to inhibit apoptosis and autophagy of SGs in the T2DM rats. Moreover, ART/Met preserved parasympathetic innervation (AChE and BDNF expression) in SGs to alleviate diabetes-induced hyposalivation likely through rescuing central SSN damage. Taken together, these findings might provide a novel rationale and treatment strategy for future treatment of diabetes-induced xerostomia in the clinic.

Metformin and its therapeutic applications in autoimmune inflammatory rheumatic disease

Metformin is a first-line therapeutic agent for type 2 diabetes. Apart from its glucose-lowering effect, metformin is attracting interest regarding possible therapeutic benefits in various other conditions. As metformin regulates cell metabolism, proliferation, growth, and autophagy, it may also modulate immune cell functions. Given that metformin acts on multiple intracellular signaling pathways, including adenosine monophosphate (AMP)-activated protein kinase (AMPK) activation, and that AMPK and its downstream intracellular signaling control the activation and differentiation of T and B cells and inflammatory responses, metformin may exert immunomodulatory and anti- inflammatory effects. The efficacy of metformin has been investigated in preclinical and clinical studies on rheumatoid arthritis, osteoarthritis, systemic lupus erythematosus, Sjögren's syndrome, scleroderma, ankylosing spondylitis, and gout. In this review, we discuss the potential mechanisms through which metformin exerts its therapeutic effects in these diseases, focusing particularly on rheumatoid arthritis and osteoarthritis.

Uncovering potential single nucleotide polymorphisms, copy number variations and related signaling pathways in primary Sjogren's syndrome

Primary Sjogren’s syndrome (pSS) is a complex systemic autoimmune disease, which is difficult to accurately diagnose due to symptom diversity in patients, especially at earlier stages. We tried to find potential single nucleotide polymorphisms (SNPs), copy number variations (CNVs) and related signaling pathways. Genomic DNA was extracted from peripheral blood of 12 individuals (7 individuals from 3 pSS pedigrees and 5 sporadic cases) for whole-exome sequencing (WES) analysis. SNPs and CNVs were identified, followed by functional annotation of genes with SNPs and CNVs. Gene expression profile (involving 64 normal controls and 166 cases) was downloaded from the Gene Expression Omnibus database (GEO) dataset for differentially expression analysis. Sanger sequencing and in vitro validation was used to validate the identified SNPs and differentially expressed genes, respectively. A total of 5 SNPs were identified in both pedigrees and sporadic cases, such as FES, PPM1J, and TRAPPC9. A total of 3402 and 19 CNVs were identified in pedigrees and sporadic cases, respectively. Fifty-one differentially expressed genes were associated with immunity, such as BATF3, LAP3, BATF2, PARP9, and IL15RA. AMPK signaling pathway and cell adhesion molecules (CAMs) were the most significantly enriched signaling pathways of identified SNPs. Identified CNVs were associated with systemic lupus erythematosus, mineral absorption, and HTLV-I infection. IL2-STAT5 signaling, interferon-gamma response, and interferon-alpha response were significantly enriched immune related signaling pathways of identified differentially expressed genes. In conclusion, our study found some potential SNPs, CNVs, and related signaling pathways, which could be useful in understanding the pathological mechanism of pSS.

Effects of metformin on autoimmune immunoglobins and interferon-γ in patients with early diagnosed pemphigus vulgaris: a prospective clinical trial

The management of pemphigus vulgaris (PV) is challenging. This study aimed to evaluate the immunomodulating effects of metformin on PV. The study was conducted in two phases: in the first phase, patients received routine first-line treatment (prednisolone plus azathioprine) for 2 months, then in the second phase, metformin was added to this regimen for another 2 months. After addition of metformin to the first-line medications, significant reductions were seen in serum IgG1 (reduced from 534.92 ± 134.83 mg/dL to 481.58 ± 130.46 mg/dL, P < 0.001), IgG4 (51.83 ± 27.26 mg/dL to 44.50 ± 26.05 mg/dL, P < 0.001) and interferon-γ (277.99 ± 108.71 pg/mL to 45.05 ± 17.080 pg/mL, P = 0.03) concentrations. The suppressant effect of metformin was greatest on IgG4 (coefficient of variation 1.28), the dominant subclass of IgG involved in PV. Metformin could have immunomodulating effects on PV with controlling effects on steroid complications.

Metformin as a Treatment Strategy for Sjögren's Syndrome

Sjögren's syndrome (SS), a chronic inflammatory disease involving the salivary and lacrimal glands, presents symptoms of sicca as well as systemic manifestations such as fatigue and musculoskeletal pain. Only a few treatments have been successful in management of SS; thus treatment of the disease is challenging. Metformin is the first-line agent for type 2 diabetes and has anti-inflammatory potential. Its immunomodulatory capacity is exerted via activation of 5' adenosine monophosphate-activated protein kinase (AMPK). Metformin inhibits mitochondrial respiratory chain complex I which leads to change in adenosine mono-phosphate (AMP) to adenosine tri-phosphate (ATP) ratio. This results in AMPK activation and causes inhibition of mammalian target of rapamycin (mTOR). mTOR plays an important role in T cell differentiation and mTOR deficient T cells differentiate into regulatory T cells. In this manner, metformin enhances immunoregulatory response in an individual. mTOR is responsible for B cell proliferation and germinal center (GC) differentiation. Thus, reduction of B cell differentiation into antibody-producing plasma cells occurs via downregulation of mTOR. Due to the lack of suggested treatment for SS, metformin has been considered as a treatment strategy and is expected to ameliorate salivary gland function.

Lycium barbarum Polysaccharide Ameliorates Sjögren's Syndrome in a Murine Model

SCOPE

This study aims to evaluate the therapeutic efficacy and mechanisms of Lycium barbarum polysaccharide (LBP) in primary Sjögren's syndrome (pSS).

METHODS AND RESULTS

Non-obese diabetic mice (the pSS model) are randomly divided into four groups: Low dose LBP (LBP.L, 5 mg kg-1  d-1 ), high dose LBP (10 mg kg-1  d-1 ), low dose interleukin (IL)-2 (25 000 IU/d), and control (saline water). Drugs were treated for 12 weeks. LBP.L significantly reduces the salivary gland inflammation compared with the control group (histological score p LBP.L vs Control  = 0.019; foci number: p LBP.L vs Control  = 0.038). LBP.L also remarkably reduces the effector follicular helper T (Tfh) cells and the CD4+ IL-17A+ helper T (Th17) cells in both spleen and cervical lymph node (cLN) cells. Additionally, the ratios of regulatory T cell (Treg)/Tfh cells and Treg/Th17 cells are substantially increased in mice treated with LBP.L in both spleen and cLNs. LBP also inhibits Th17 and Tfh cells and markedly increases the Treg/Tfh ratio in human peripheral blood mononuclear cells.

CONCLUSION

LBP.L inhibits the progression of pSS in mice, associated with modulation of T cell differentiation.

Metformin ameliorates scleroderma via inhibiting Th17 cells and reducing mTOR-STAT3 signaling in skin fibroblasts

Scleroderma is an autoimmune disease that causes dermal fibrosis. It occurs when collagen accumulates in tissue as a result of persistent inflammation. Th17 cells and pro-inflammatory cytokines such as IL-1β, IL-6, IL-17, and TNF-α play important roles in the pathogenesis of scleroderma. Because metformin, a medication used to treat diabetes, has effective immunoregulatory functions, we investigated its therapeutic function in scleroderma. Mice in a model of bleomycin-induced scleroderma were treated with metformin for 2 weeks. Histological assessment demonstrated protective effects of metformin against scleroderma. Metformin decreased the expression of pro-inflammatory factors in dermal tissue and lymphocytes. It also decreased mRNA expression of pro-inflammatory cytokines (IL-1β, IL-6, IL-17, and TNF-α) and fibrosis-inducing molecules both in vivo and in vitro. These results suggest that metformin treatment has anti-inflammatory effects on lymphocytes via the inhibition of IL-17 and cytokines related to Th17 differentiation, such as IL-1β, IL-6, and TNF-α. To investigate how metformin modulates the inflammatory process in skin fibroblasts, we measured mTOR-STAT3 signaling in skin fibroblasts and found that phosphorylated mTOR and phosphorylated STAT3 protein expression were decreased by metformin treatment. These results suggest that metformin has potential to treat scleroderma by inhibiting pro-inflammatory cytokines and anti-inflammatory activity mediated by mTOR-STAT3 signaling.

Therapies Targeting Trained Immune Cells in Inflammatory and Autoimmune Diseases

The concept of trained immunity has recently emerged as a mechanism contributing to several immune mediated inflammatory conditions. Trained immunity is defined by the immunological memory developed in innate immune cells after a primary non-specific stimulus that, in turn, promotes a heightened inflammatory response upon a secondary challenge. The most characteristic changes associated to this process involve the rewiring of cell metabolism and epigenetic reprogramming. Under physiological conditions, the role of trained immune cells ensures a prompt response. This action is limited by effective resolution of inflammation and tissue repair in order to restore homeostasis. However, unrestrained activation of innate immune cells contributes to the development of chronic inflammation and tissue destruction through the secretion of inflammatory cytokines, proteases and growth factors. Therefore, interventions aimed at reversing the changes induced by trained immunity provide potential therapeutic approaches to treat inflammatory and autoimmune diseases like rheumatoid arthritis (RA). We review cellular approaches that target metabolism and the epigenetic reprogramming of dendritic cells, macrophages, natural killer cells, and other trained cells in the context of autoimmune inflammatory diseases.

Follicular helper T cells and follicular regulatory T cells in the immunopathology of primary Sjögren's syndrome

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease, characterized by lymphocytic infiltration into exocrine glands, which causes dry eyes, dry mouth, and systemic damage. Although the precise etiology of pSS is not clear yet, highly activated B cells, abundant anti-SSA/Ro, and anti-SSB/La autoantibodies are the hallmarks of this disease. Follicular helper T cells (Tfh), a subset of CD4⁺ T cells, with cell surface receptors PD-1 and CXCR5, express ICOS, transcription factor Bcl-6, and a cytokine IL-21. These cells help in the differentiation of B cells into plasma cells and stimulate the formation of germinal center (GC). Previous studies have demonstrated abundant Tfh cells in the peripheral blood and salivary glands (SGs) of the patients with pSS, correlated with extensive lymphocytic infiltration of the SGs and high disease activity scores. Patients with pSS who are treated with abatacept (CTLA-4 Ig) show fewer circulating Tfh cells, reduced expression of ICOS, and lower disease activity scores. Recently identified follicular regulatory T (Tfr) cells, a subset of regulatory T cells, control the function of Tfh cells and the GC reactions. Here, we summarize the observed alterations in Tfh and Tfr cell numbers, activation state, and circulating subset distribution in pSS. Our goal is to improve the understanding of the roles of Tfh and Tfr cells (surface marker expression, cytokine production, and transcription factors) in the pathogenesis of pSS, thus contributing to the identification of candidate therapeutic agents for this disease.

Metformin: A Potential Therapeutic Tool for Rheumatologists

Metformin is an oral antihyperglycemic drug widely used to treat type 2 diabetes, acting via indirect activation of 5′ Adenosine Monophosphate-activated Protein Kinase (AMPK). Actually, evidence has accumulated of an intriguing anti-inflammatory activity, mainly mediated by AMPK through a variety of mechanisms such as the inhibition of cytokine-stimulated Nuclear Factor-κB (NF-κB) and the downregulation of the Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) signaling pathways. Moreover, AMPK plays an important role in the modulation of T lymphocytes and other pivotal cells of the innate immune system. The current understanding of these AMPK effects provides a strong rationale for metformin repurposing in the management of autoimmune and inflammatory conditions. Several studies demonstrated metformin’s beneficial effects on both animal and human rheumatologic diseases, especially on rheumatoid arthritis. Unfortunately, even though data are large and remarkable, they almost exclusively come from experimental investigations with only a few from clinical trials. The lack of support from prospective placebo-controlled trials does not allow metformin to enter the therapeutic repertoire of rheumatologists. However, a large proportion of rheumatologic patients can currently benefit from metformin, such as those with concomitant obesity and type 2 diabetes, two conditions strongly associated with rheumatoid arthritis, osteoarthritis, and gout, as well as those with diabetes secondary to steroid therapy.

Metformin enhances the immunomodulatory potential of adipose-derived mesenchymal stem cells through STAT1 in an animal model of lupus

OBJECTIVES

Mesenchymal stem cells (MSCs) are considered potential therapeutic agents for treating autoimmune disease because of their immunomodulatory capacities and anti-inflammatory effects. However, several studies have shown that there is no consistency in the effectiveness of the MSCs to treat autoimmune disease, including SLE. In this study, we investigated whether metformin could enhance the immunoregulatory function of MSCs, what mechanism is relevant, and whether metformin-treated MSCs could be effective in an animal lupus model.

METHODS

Adipose-derived (Ad)-MSCs were cultured for 72 h in the presence of metformin. Immunoregulatory factors expression was analysed by real-time PCR and ELISA. MRL/lpr mice weekly injected intravenously with 1 × 106 Ad-MSCs or metformin-treated Ad-MSCs for 8 weeks. 16-week-old mice were sacrificed and proteinuria, anti-dsDNA IgG antibody, glomerulonephritis, immune complex, cellular subset were analysed in each group.

RESULTS

Metformin enhanced the immunomodulatory functions of Ad-MSCs including IDO, IL-10 and TGF-β. Metformin upregulated the expression of p-AMPK, p-STAT1 and inhibited the expression of p-STAT3, p-mTOR in Ad-MSCs. STAT1 inhibition by siRNA strongly diminished IDO, IL-10, TGF-β in metformin-treated Ad-MSCs. As a result, metformin promoted the immunoregulatory effect of Ad-MSCs by enhancing STAT1 expression, which was dependent on the AMPK/mTOR pathway. Administration of metformin-treated Ad-MSCs resulted in significant disease activity improvement including inflammatory phenotype, glomerulonephritis, proteinuria and anti-dsDNA IgG antibody production in MRL/lpr mice. Moreover, metformin-treated Ad-MSCs inhibited CD4-CD8- T-cell expansion and Th17/Treg cell ratio.

CONCLUSION

Metformin optimized the immunoregulatory properties of Ad-MSCs and may be a novel therapeutic agent for the treatment of lupus.

Impact of metformin on immunological markers: Implication in its anti-tumor mechanism

Metformin, an anti-hyperglycemic drug, has been known to have antitumor properties for around 15 years. Although there are a number of reports attributing the antitumor function of metformin to its impact on energy homeostasis and oxygen re-distribution in tumor microenvironment, detailed mechanisms remain largely unknown. In the past several years, there is an increasing number of publications indicating that metformin can affect various immunological components including lymphocytes, macrophages, cytokines and several key immunological molecules in both human and animal studies. These interesting results appear to be in line with emerging data that suggest associations between immune responses and energy homeostasis/oxygen re-distribution, which may explain effective impacts of metformin on immunotherapies against autoimmune diseases as well as cancers. This review article is to analyse and discuss recent development in the above areas with aim to justify metformin as a new adjuvant for immunotherapy against human cancers. We hope that our summary will help to optimize the application of metformin for various types of human cancers.

Hyperglycemia and Salivary Gland Dysfunction in the Non-obese Diabetic Mouse: Caveats for Preclinical Studies in Sjögren's Syndrome

The Non-obese Diabetic (NOD) mouse model for type I diabetes also develops some features of Sjögren’s syndrome (SS). Since the source of the mice and the environment exert a strong influence on diabetes, this study investigated SS development in NOD mice obtained from two vendors. Female NOD mice from The Jackson Laboratory (JAX) and Taconic Biosciences were monitored for blood glucose and pilocarpine-induced salivation. The gut microbiome was analyzed by 16S rRNA sequencing of stool DNA. At euthanasia, serum cytokines and sialoadenitis severity were evaluated. The onset of diabetes was significantly accelerated in JAX mice compared to Taconic mice. Although the gut microbiome between the two groups was distinct, both groups developed sialoadenitis. There was no correlation between the severity of sialoadenitis and reduced saliva production. Instead, salivary gland dysfunction was associated with hyperglycemia and elevation of serum IL1β, IL16, and CXCL13. Our data suggest that inflammatory pathways linked with hyperglycemia are confounding factors for salivary gland dysfunction in female NOD mice, and might not be representative of the mechanisms operative in SS patients. Considering that NOD mice have been used to test numerous experimental therapies for SS, caution needs to be exerted before advancing these therapeutics for human trials.