RhoA/ROCK-dependent pathway is required for TLR2-mediated IL-23 production in human synovial macrophages: suppression by cilostazol

Novel insights into gut health: Cilostazol strengthens gut integrity by adjusting TLR-2/NF-κB/IL-23 and CD44/AKT/GSK-3β/cyclin-D1 trajectories in methotrexate-induced mucositis model

Methotrexate (MTX)-induced gastrointestinal mucositis is a common adverse effect characterized by redox imbalance and overproduction of inflammatory mediators that perturb intestinal integrity. Currently, there is no definitive treatment for this condition and its prevention is still far beyond comprehension. Because of its pleiotropic pharmacological actions, we aimed to explore the potential mechanisms through which cilostazol (CILO) can protect against MTX-induced intestinal mucositis. Wistar rats were allocated into 4 groups, control, CILO (100 mg/kg, p.o for 14 days), MTX (7.5 mg/kg for 4 successive days), and CILO + MTX. The improving effect of CILO on the morphological structure was confirmed by an upturn in the histopathological and transition electron microscope examinations evidenced by the increased jejunal villus height/width and the crypt depth besides the maintenance of tight junctions. These findings were verified biochemically; on the molecular level, CILO reduced the MTX-induced lipid peroxidation, cleaved caspase-3, p53, and the inflammatory parameters (TLR-2, NF-κB, IL-23, TNF-α, IL-1β), while increasing the anti-inflammatory marker IL-10 and the antioxidant enzyme SOD. Moreover, CILO decreased the injurious axis AKT/GSK-3β/cyclin-D1, and CD44+, but increased the immunoexpression of the cell proliferating marker PCNA. CILO also upheld the intestinal barrier by enhancing the tight junction molecules (ZO-1, claudin-4) and the E-cadherin/β-catenin complex while abating the mesenchymal marker vimentin. In conclusion, CILO protected gut integrity by reducing the epithelial-mesenchymal transition process, the MTX-induced oxidative, apoptotic, and inflammatory mediators, and turning off the CD44/AKT/GSK-3β/cyclin D1 trajectory and intensifying the expression of PCNA.

Navigating the landscape of Rho GTPase signalling system in autoimmunity: A bibliometric analysis spanning over three decades (1990 to 2023)

Ras-homologous (Rho) guanosine triphosphatases (GTPases) are considered a central player in regulating various biological processes, extending to immune regulation. Perturbations in Rho GTPase signalling have been implicated in immune-related dysregulation, contributing to the development of autoimmunity. This study presents a scientometric analysis exploring the interlink between the Rho GTPase signalling system and autoimmunity, while also delving into the trends of past studies. A total of 967 relevant publications from 1990 to 2023 were retrieved from the Web of Science Core Collection database after throrough manual filtering of irrelevant articles. The findings show an upward trajectory in publications related to this field since 2006. Over the past three decades, the United States of America (41.68%) emerged as the primary contributor in advancing our understanding of the association between the Rho GTPase signalling system and autoimmunity. Research in autoimmunity has mainly centered around therapeutic interventions, with an emphasis on studying leukocyte (macrophage) and endothelial remodelling. Interestingly, within the domains of multiple sclerosis and rheumatoid arthritis, the current focus has been directed towards comprehending the role of RhoA, Rac1, and Cdc42. Notably, certain subfamilies of Rho (such as RhoB and RhoC), Rac (including Rac2 and RhoG), Cdc42 (specifically RhoJ), and other atypical Rho GTPases (like RhoE and RhoH) consistently demonstrating compelling link with autoimmunity, but still warrants emphasis in the future study. Hence, strategic manipulation of the Rho signalling system holds immense promise as a pivotal approach to addressing the global challenge of autoimmunity.

The anti-platelet drug cilostazol enhances heart rate and interrenal steroidogenesis and exerts a scant effect on innate immune responses in zebrafish

RATIONALE

Cilostazol, an anti-platelet phosphodiesterase-3 inhibitor used for the treatment of intermittent claudication, is known for its pleiotropic effects on platelets, endothelial cells and smooth muscle cells. However, how cilostazol impacts the endocrine system and the injury-induced inflammatory processes remains unclear.

METHODS

We used the zebrafish, a simple transparent model that demonstrates rapid development and a strong regenerative ability, to test whether cilostazol influences heart rate, steroidogenesis, and the temporal and dosage effects of cilostazol on innate immune cells during tissue damage and repair.

RESULTS

While dosages of cilostazol from 10 to 100 μM did not induce any noticeable morphological abnormality in the embryonic and larval zebrafish, the heart rate was increased as measured by ImageJ TSA method. Moreover, adrenal/interrenal steroidogenesis in larval zebrafish, analyzed by whole-mount 3β-Hsd enzymatic activity and cortisol ELISA assays, was significantly enhanced. During embryonic fin amputation and regeneration, cilostazol treatments led to a subtle yet significant effect on reducing the aggregation of Mpx-expressing neutrophil at the lesion site, but did not affect the immediate injury-induced recruitment and retention of Mpeg1-expressing macrophages.

CONCLUSIONS

Our results indicate that cilostazol has a significant effect on the heart rate and the growth as well as endocrine function of steroidogenic tissue; with a limited effect on the migration of innate immune cells during tissue damage and repair.

Synovial Macrophages: Past Life, Current Situation, and Application in Inflammatory Arthritis

Inflammatory arthritis is an inflammatory disease that involves the joints and surrounding tissues. Synovial hyperplasia often presents when joints become inflamed due to immune cell infiltration. Synovial membrane is an important as well as a highly specific component of the joint, and its lesions can lead to degeneration of the joint surface, causing pain and joint disability or affecting the patients’ quality of life in severe cases. Synovial macrophages (SMs) are one of the cellular components of the synovial membrane, which not only retain the function of macrophages to engulf foreign bodies in the joint cavity, but also interact with synovial fibroblasts (SFs), T cells, B cells, and other inflammatory cells to promote the production of a variety of pro-inflammatory cytokines and chemokines, such as TNF-α, IL-1β, IL-8, and IL-6, which are involved in the pathogenic process of inflammatory arthritis. SMs from different tissue sources have differently differentiated potentials and functional expressions. This article provides a summary on studies pertaining to SMs in inflammatory arthritis, and explores their role in its treatment, in order to highlight novel treatment modalities for the disease.

Rho GTPase signaling in rheumatic diseases

Rho guanosine triphosphatase (GTPases), as molecular switches, have been identified to be dysregulated and involved in the pathogenesis of various rheumatic diseases, mainly including rheumatoid arthritis, osteoarthritis, systemic sclerosis, and systemic lupus erythematosus. Downstream pathways involving multiple types of cells, such as fibroblasts, chondrocytes, synoviocytes, and immunocytes are mediated by activated Rho GTPases to promote pathogenesis. Targeted therapy via inhibitors of Rho GTPases has been implicated in the treatment of rheumatic diseases, demonstrating promising effects. In this review, the effects of Rho GTPases in the pathogenesis of rheumatic diseases are summarized, and the Rho GTPase-mediated pathways are elucidated. Therapeutic strategies using Rho GTPase inhibitors in rheumatic diseases are also discussed to provide insights for further exploration of targeted therapy in preclinical studies and clinical practice. Future directions on studies of Rho GTPases in rheumatic diseases based on current understandings are provided.

Rho-Kinase as a Target for Cancer Therapy and Its Immunotherapeutic Potential

Cancer immunotherapy is fast rising as a prominent new pillar of cancer treatment, harnessing the immune system to fight against numerous types of cancer. Rho-kinase (ROCK) pathway is involved in diverse cellular activities, and is therefore the target of interest in various diseases at the cellular level including cancer. Indeed, ROCK is well-known for its involvement in the tumor cell and tumor microenvironment, especially in its ability to enhance tumor cell progression, migration, metastasis, and extracellular matrix remodeling. Importantly, ROCK is also considered to be a novel and effective modulator of immune cells, although further studies are needed. In this review article, we describe the various activities of ROCK and its potential to be utilized in cancer treatment, particularly in cancer immunotherapy, by shining a light on its activities in the immune system.

IL-23 orchestrating immune cell activation in arthritis

IL-23 is a cytokine member of the IL-12 superfamily. These heterodimeric cytokines offer broad immune regulatory activity with potential effector function in inflammatory arthritis. IL-23 is a pro-inflammatory cytokine secreted by dendritic cells and macrophages. It plays a key role in both innate and adaptive immunity. By promoting and maintaining T cell differentiation into Th17 T cells, IL-23 is a key player in the pathogenesis of rheumatic diseases. Data from pre-clinical IL-23 knockout models show the major importance of IL-23 in development of arthritis. The induction and maintenance of type 17 cells, which secrete IL-17A and other pro-inflammatory cytokines, contributes to local synovial inflammation and skin inflammation in PsA, and perhaps in RA. Commensurate with this, therapeutic strategies targeting IL-23 have proven efficient in PsA in several studies, albeit not yet in RA.

Could cilostazol be beneficial in COVID-19 treatment? Thinking about phosphodiesterase-3 as a therapeutic target

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19) that has emerged and rapidly spread across the world. The COVID-19 severity is associated to viral pneumonia with additional extrapulmonary complications. Hyperinflammation, dysfunctional immune response and hypercoagulability state are associated to poor prognosis. Therefore, the repositioning of multi-target drugs to control the hyperinflammation represents an important challenge for the scientific community. Cilostazol, a selective phosphodiesterase type-3 inhibitor (PDE-3), is an antiplatelet and vasodilator drug, that presents a range of pleiotropic effects, such as antiapoptotic, anti-inflammatory, antioxidant, and cardioprotective activities. Cilostazol also can inhibit the adenosine uptake, which enhances intracellular cAMP levels. In the lungs, elevated cAMP promotes anti-fibrotic, vasodilator, antiproliferative effects, as well as mitigating inflammatory events. Interestingly, a recent study evaluated antiplatelet FDA-approved drugs through molecular docking-based virtual screening on viral target proteins. This study revealed that cilostazol is a promising drug against COVID-19 by inhibiting both main protease (M^pro) and Spike glycoprotein, reinforcing its use as a promising therapeutic approach for COVID-19. Considering the complexity associated to COVID-19 pathophysiology and observing its main mechanisms, this article raises the hypothesis that cilostazol may act on important targets in development of the disease. This review highlights the importance of drug repurposing to address such an urgent clinical demand safely, effectively and at low cost, reinforcing the main pharmacological actions, to support the hypothesis that a multi-target drug such as cilostazol could play an important role in the treatment of COVID-19.

Etidronate down-regulates Toll-like receptor 2 ligand-induced chemokine production by inhibiting MyD88 expression and NF-κB activation

OBJECTIVE

Pretreatment of J774.1 cells with etidronate, a non-nitrogen-containing bisphosphonate (non-NBP) used as an antibone resorptive drug, was previously reported to inhibit Toll-like receptor (TLR) 2 agonist-induced proinflammatory cytokine production. The present study aimed to examine the effects of etidronate on chemokine production by human monocytic U937 cells incubated with Pam₃Cys-Ser-(Lys)₄ (Pam₃CSK₄, a TLR2 ligand) and lipid A (a TLR4 ligand).

METHODS

U937 cells were pretreated with or without etidronate, and then incubated with or without Pam₃CSK₄ or lipid A. Levels of secreted human interleukin (IL)-8 and monocyte chemoattractant protein-1 (MCP-1) in culture supernatants and activation of nuclear factor-κB (NF-κB) p65 were measured by enzyme-linked immunosorbent assay (ELISA). Cytotoxicity was determined by measuring lactate dehydrogenase (LDH) activity in supernatants. Expression of intracellular adhesion molecule (ICAM)-1 and MyD88 was analyzed by flow cytometry and Western blot analysis, respectively.

RESULTS

Etidronate down-regulated IL-8 and MCP-1 production and NF-κB p65 activation induced by Pam₃CSK_4, but not lipid A, in U937 cells. Etidronate also inhibited MyD88 expression in U937 cells incubated with Pam₃CSK₄.

CONCLUSION

Etidronate down-regulates IL-8 and MCP-1 production in U937 cells by inhibiting both the expression of MyD88 and activation of NF-κB p65 in the TLR2, but not TLR4, pathway.

Control of GM-CSF-Dependent Dendritic Cell Differentiation and Maturation by DEF6 and SWAP-70

Although GM-CSF has been widely used in dendritic cell (DC) research, the mechanisms, factors, and signals regulating steady-state differentiation and maturation of GM-CSF-dependent DCs are insufficiently known. We found that the absence, individually or combined, of the related proteins DEF6 and SWAP-70 strongly enhances differentiation of murine GM-CSF-derived DCs. Contrasting SWAP-70, control through DEF6 does not depend on RHOA activation. DEF6 deficiency leads to expression of the DC-specific transcription factor ZBTB46 and prolonged STAT5 activation in GM-CSF cultures. SWAP-70 and DEF6-mediated restriction of DC differentiation converges mechanistically at the NF-κB pathway. DEF6 acts at early stages of DC differentiation in CD115^-cKIT⁺ myeloid DC progenitors, whereas SWAP-70 acts subsequently. SWAP-70 and DEF6 regulate steady-state DC cytokine expression as well as in vivo accumulation in lymphatic tissue of migratory DCs. Our studies thus elucidate previously unknown roles of two closely related factors with distinct and complementary activities in DC differentiation and steady-state DC function.

Cilostazol Mediates Immune Responses and Affects Angiogenesis During the Acute Phase of Hind Limb Ischemia in a Mouse Model

BACKGROUND

Cilostazol is a drug of choice for the treatment of intermittent claudication that also affects innate and adaptive immune cells. The purpose of our study was the evaluation of cilostazol's impact on the immune and angiogenic response in murine models of hind limb ischemia.

METHODS

We used 108 immunodeficient NOD.CB17-Prkdcscid/J mice and 108 wild-type CB17 mice. At day 0 (D0), all animals underwent hind limb ischemia. Half of them in both groups received daily cilostazol starting at D0 and for the next 7 postoperative days, while the rest of them served as controls, receiving vehicle. Interleukin (IL) 2, IL-4, IL-6, IL-10, IL-17A, tumor necrosis factor α (TNF-α), and interferon γ (IFN-γ) serum concentrations were measured by flow cytometry on postsurgery days D1, D3, D5, and D7. On D7, both groups underwent positron emission tomography scan with ⁶⁸Ga-RGD. Mice were euthanatized and gastrocnemius muscles were obtained for histological evaluation.

RESULTS

There was a statistically significant augmentation (P < .05) in IL-4, IL-10, IL-6, and IFN-γ concentrations in treated CB17 animals, while IL-2 was significantly suppressed. Significant difference was detected between the CiBisch and Bisch groups on D1 and D7 (P < .05) in CD31 staining. In treated NOD.CB17 animals, TNF-α, IL-6, and IFN-γ presented significant augmentation, while ⁶⁸Ga-NODAGA-RGDfK uptake and CD31 expression were found significantly lower for both legs in comparison to the control.

CONCLUSION

Cilostazol seems to significantly increase angiogenesis in wild-type animals during the first postoperational week. It also influences immune cells, altering the type of immune response by promoting anti-inflammatory cytokine production in wild-type animals, while it helps toward inflammation regression in immunodeficient animals.

STING-mediated inflammation in Kupffer cells contributes to progression of nonalcoholic steatohepatitis

Innate immune activation contributes to the transition from nonalcoholic fatty liver to nonalcoholic steatohepatitis (NASH). Stimulator of IFN genes (STING, also referred to Tmem173) is a universal receptor that recognizes released DNA and triggers innate immune activation. In this work, we investigated the role of STING in the progression of NASH in mice. Both methionine- and choline-deficient diet (MCD) and high-fat diet (HFD) were used to induce NASH in mice. Strikingly, STING deficiency attenuated steatosis, fibrosis, and inflammation in livers in both murine models of NASH. Additionally, STING deficiency increased fasting glucose levels in mice independently of insulin, but mitigated HFD-induced insulin resistance and weight gain and reduced levels of cholesterol, triglycerides, and LDL in serum; it also enhanced levels of HDL. The mitochondrial DNA (mtDNA) from hepatocytes of HFD-fed mice induced TNF-α and IL-6 expression in cultured Kupffer cells (KCs), which was attenuated by STING deficiency or pretreatment with BAY11-7082 (an NF-κB inhibitor). Finally, chronic exposure to 5,6-dimethylxanthenone-4-acetic acid (DMXAA, a STING agonist) led to hepatic steatosis and inflammation in WT mice, but not in STING-deficient mice. We proposed that STING functions as an mtDNA sensor in the KCs of liver under lipid overload and induces NF-κB-dependent inflammation in NASH.

The selective ROCK2 inhibitor KD025 reduces IL-17 secretion in human peripheral blood mononuclear cells independent of IL-1 and IL-6

Reducing the activities of the pro-inflammatory cytokine IL-17 is an effective treatment strategy for several chronic autoimmune disorders. Rho-associated coiled-coil containing kinase 2 (ROCK2) is a member of the serine-threonine protein kinase family that regulates IL-17 secretion in T cells via signal transducer and activator of transcription 3 (STAT3)-dependent mechanism. We reported here that the selective ROCK2 inhibitor KD025 significantly reduced in vitro production of IL-17 in unfractionated human peripheral blood mononuclear cells (PBMCs) stimulated with the dectin-1 agonist Candida albicans. C. albicans induced IL-17 was reduced by 70% (p < 0.0001); a similar reduction (80%) was observed in PBMC stimulated with the Toll-like receptor 2 agonist Staphylococcus epidermidis (p < 0.0001). Treatment of PBMC with KD025 was not associated with a reduction in IL-1β, IL-6 or IL-1α levels; in contrast, a 1.5 fold increase in the level of IL-1 receptor antagonist (IL-1Ra) was observed (p < 0.001). KD025 down-regulated C. albicans-induced Myosin Light Chain and STAT3, whereas STAT5 phosphorylation increased. Using anti-CD3/CD28 activation of the TCR, KD025 similarly suppressed IL-17 independent of a reduction in IL-1β. Thus, ROCK2 directly regulates IL-17 secretion independent of endogenous IL-1 and IL-6 supporting development of selective ROCK2 inhibitors for treatment of IL-17-driven inflammatory diseases.

Anti-inflammatory properties of cilostazol: Its interruption of DNA binding activity of NF-κB from the Toll-like receptor signaling pathways

Cilostazol, a selective inhibitor of phosphodiesterase type III with anti-platelet, anti-mitogenic, and vasodilating properties, is widely used to treat ischemic symptoms of peripheral vascular disease. Ample evidence has suggested that cilostazol also exhibits an anti-inflammatory effect, but its anti-inflammatory mechanism is not fully understood. Here, we showed that cilostazol specifically inhibited expression of cytokines, which are induced by nuclear factor-κB (NF-κB) activation, in RAW264.7 macrophage cells stimulated with different Toll-like receptor (TLR) ligands. Cilostazol was found to significantly reduce TLR-4 and TLR-3 ligands-stimulated NF-κB transcriptional activity, which was quantified by luciferase reporter assays. However, cilostazol was without effect on IκBα degradation and NF-κB p65 phosphorylation and nuclear translocation after challenge with the TLR-4 ligand lipopolysaccharide (LPS). Cilostazol did not also prevent the LPS-induced increase in phosphorylated levels of the mitogen-activated protein kinase (MAPK) family. On the other hand, using chromatin immunoprecipitation assays, we demonstrated that cilostazol reduced the LPS-induced transcriptional activities of interleukin-6 and tumor necrosis factor-α by preventing the recruitment of NF-κB p65 to these gene promoters. When cilostazol was given to mice by oral gavage daily for 7 days, LPS-induced aberrant pro-inflammatory cytokine production and end-organ tissue injury were significantly reduced. The results of this study suggest that cilostazol is capable of directly interrupting DNA binding activity of NF-κB proteins from the TLR signaling pathways. The therapy to specifically intervene in this pathway may be potentially beneficial for the prevention of different inflammatory disorders.

The role of IL-23 receptor signaling in inflammation-mediated erosive autoimmune arthritis and bone remodeling

The IL‐23/Th17 axis has been implicated in the development of autoimmune diseases, such as rheumatoid arthritis (RA) and psoriatic arthritis (PsA). RA and PsA are heterogeneous diseases with substantial burden on patients. Increasing evidence suggests that the IL‐23 signaling pathway may be involved in the development of autoimmunity and erosive joint damage. IL‐23 can act either directly or indirectly on bone forming osteoblasts as well as on bone resorbing osteoclasts. As IL‐23 regulates the activity of cells of the bone, it is conceivable that in addition to inflammation‐mediated joint erosion, IL‐23 may play a role in physiological bone remodeling. In this review, we focus on the role of IL‐23 in autoimmune arthritis in patients and murine models, and provide an overview of IL‐23 producing and responding cells in autoimmune arthritic joints. In addition, we discuss the role of IL‐23 on bone forming osteoblasts and bone resorbing osteoclasts regarding inflammation‐mediated joint damage and bone remodeling. At last, we briefly discuss the clinical implications of targeting this pathway for joint damage and systemic bone loss in autoimmune arthritis.

Etidronate down-regulates Toll-like receptor (TLR) 2 ligand-induced proinflammatory cytokine production by inhibiting NF-κB activation

BACKGROUND

Etidronate is a non-nitrogen-containing bisphosphonate (non-NBP) used for anti-bone resorptive therapy as well as having inhibitory effects on atherosclerotic plaques. The present study examined the effects of etidronate on the production of proinflammatory cytokines and chemokines by the macrophage-like cell line, J774.1, incubated with Pam₃Cys-Ser-(Lys)₄ (Pam₃CSK₄, a Toll-like receptor (TLR) 2 agonist) and lipid A (a TLR4 agonist).

METHODS

J774.1 cells and human monocytic THP-1 cells were pretreated with or without etidronate for 5min, and then incubated with or without Pam₃CSK₄ or lipid A for 24h. Levels of secreted interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), and macrophage inflammatory protein-1α (MIP-1α) in culture supernatants were measured by enzyme-linked immunosorbent assay (ELISA). Cytotoxicity was determined by LDH activity in the supernatants. We also examined the effects of etidronate on the activation of nuclear factor-κB (NF-κB) and p38 mitogen-activated protein kinase (MAPK) in J774.1 cells by ELISA and Western blotting.

RESULTS

Treatment of J774.1 cells with etidronate down-regulated TLR2 ligand-induced production of IL-6, TNF-α, MCP-1, and MIP-1α. Etidronate also inhibited Pam₃CSK₄-induced MCP-1 and TNF-α production by THP-1 cells. However, etidronate did not induce cytotoxicity and reduced lipid A-induced cytotoxicity in J774.1 cells. In addition, this agent did not down-regulate TLR4 ligand-induced proinflammatory cytokine production. Furthermore, etidronate inhibited the translocation of NF-κB but not p38 MAPK in J774.1 cells stimulated with Pam₃CSK₄ or lipid A.

CONCLUSION

Etidronate likely inhibits proinflammatory cytokine production in J774.1 cells by suppressing NF-κB activation in the TLR2 and not the TLR4 pathway.

Salidroside ameliorates arthritis-induced brain cognition deficits by regulating Rho/ROCK/NF-κB pathway

The prevalence of cognitive impairment in rheumatoid arthritis (RA) patients was increasingly serious nowadays. The purpose of the current study was to explore whether salidroside (Sal) could alleviate arthritis-induced cognition deficits and examine the relationship between the impairment and Rho/ROCK/NF-κB pathway. Collagen-induced arthritis (CIA) was established by the injection of chicken type II collagen (CII), complete Freund's adjuvant (CFA) and incomplete Freund's adjuvant (IFA). Arthritic lesions of CIA rats were assessed by arthritis index score, swelling of paws and histological analysis. Cognitive deficits symptoms of CIA rats were monitored through Morris water maze test. The contents of pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β) and interleukin-6 (IL-6) in hippocampus and serum were significantly reduced with salidroside (20 mg/kg, 40 mg/kg) treatment compared with those in the CIA group. In parallel, we demonstrated that the expressions of RhoA, ROCK1, ROCK2, p-NF-κBp65, p-IκBα, p-IKKα and p-IKKβ were enhanced accompanying the investigation arthritis-induced cognition deficits, which were remarkably down-regulated by salidroside and confirmed by the results obtained from western blot and immunohistochemistry. LC-MS/MS results ascertained that Sal could enter into the blood and brain tissues to exhibit the protective effect on arthritis-induced cognitive dysfunction. Therefore, it was assumed that Sal might be a potential therapeutic candidate to treat arthritis-induced brain cognition deficits through the regulation of Rho/ROCK/NF-κB signaling.

Toll-like receptor 2 mediates vascular contraction and activates RhoA signaling in vascular smooth muscle cells from STZ-induced type 1 diabetic rats

Increased vascular smooth muscle cell (VSMC) contraction is an early and critical contributor to the pathogenesis of vascular dysfunction in diabetes; however, knowledge regarding the underlying mechanisms is scarce. Toll-like receptor 2 (TLR2), a well-known component of the innate immunity, is expressed in VSMC and recently has been identified to be systemically activated in diabetes. Whether TLR2 is locally activated in the diabetic blood vessels and have effect on contraction is not known. In the current study, we examined the role of TLR2 in increased vascular contraction in diabetes. Utilizing rat model of type 1 diabetes (induced by streptozotocin (STZ)), we demonstrated that aortas from STZ-diabetic rats exhibit increased expression of TLR2 and its adaptor protein, myeloid differentiation primary response 88 (MyD88), as well as enhanced protein-protein interaction between TLR2 and MyD88, suggesting a TLR2 signaling activation. Blockade of TLR2 in intact aortas using anti-TLR2 antibody attenuated increased vascular contraction in STZ-diabetic rat as assessed by wire myograph. Activation of TLR2 by specific ligand in primary aortic VSMC cultures triggered activation of RhoA which was exacerbated in cells from STZ-diabetic rats than control rats. Activation of RhoA was accompanied by phosphorylation and therefore activation of its downstream targets myosin phosphatase target subunit I and myosin light chain (markers of VSMC contraction). Taken together, these results provide evidence for the role of TLR2 in increased contraction in diabetic blood vessels that involves RhoA signaling. Thus, targeting vascular TLR2 offers a promising drug target to treat vascular dysfunction in diabetes.