Blockade of Toll-Like Receptor 4 Attenuates Erectile Dysfunction in Diabetic Rats

Nitric Oxide Resistance in Priapism Associated with Sickle Cell Disease: Mechanisms, Therapeutic Challenges, and Future Directions

Patients with sickle cell disease (SCD) display priapism, a prolonged penile erection in the absence of sexual arousal. The current pharmacological treatments for SCD-associated priapism are limited and focused on acute interventions rather than prevention. Thus, there is an urgent need for new drug targets and preventive pharmacological therapies for this condition. This review focuses on the molecular mechanisms linked to the dysfunction of the NO-cyclic guanosine monophosphate (cGMP)-phosphodiesterase type 5 (PDE5) pathway implicated in SCD-associated priapism. In murine models of SCD, reduced nitric oxide (NO)-cGMP bioavailability in the corpus cavernosum is associated with elevated plasma hemoglobin levels, increased reactive oxygen species levels that inactive NO, and testosterone deficiency that leads to endothelial nitric oxide synthase downregulation. We discuss the consequences of the reduced cGMP-dependent PDE5 activity in response to these molecular changes, highlighting it as the primary pathophysiological mechanism leading to excessive corpus cavernosum relaxation, culminating in priapism. We also further discuss the impact of intravascular hemolysis on therapeutic approaches, present current pharmacological strategies targeting the NO-cGMP-PDE5 pathway in the penis, and identify potential pharmacological targets for future priapism therapies. In men with SCD and priapism, PDE5 inhibitor therapy and testosterone replacement have shown promising results. Recent preclinical research reported the beneficial effect of treatment with haptoglobin and NO donors. SIGNIFICANCE STATEMENT: This review discusses the molecular changes that reduce NO-cGMP bioavailability in the penis in SCD and highlights pharmacological targets and therapeutic strategies for the treatment of priapism, including PDE5 inhibitors, hormonal modulators, NO donors, hydroxyurea, soluble guanylate cyclase stimulators, haptoglobin, hemopexin, and antioxidants.

Cardiometabolic Disorder and Erectile Dysfunction

Erectile dysfunction (ED), which is defined as the inability to attain and maintain a satisfactory penile erection to sufficiently permit sexual intercourse, is a consequence and also a cause of cardiometabolic disorders like diabetes mellitus, systemic hypertension, central obesity, and dyslipidemia. Although there are mounting and convincing pieces of evidence in the literature linking ED and cardiometabolic disorders, impairment of nitric oxide-dependent vasodilatation seems to be the primary signaling pathway. Studies have also implicated the suppression of circulating testosterone, increased endothelin-1, and hyperactivation of Ang II/ATIr in the pathogenesis of ED and cardiometabolic disorders. This study provides comprehensive details of the association between cardiometabolic disorders and ED and highlights the mechanisms involved. This would open areas to be explored as therapeutic targets in the management of ED and cardiometabolic disorders. It also provides sufficient evidence establishing the need for the management of cardiometabolic disorders as an adjunct therapy in the management of ED.

The pathogenic role of the immune system in erectile dysfunction and Peyronie's disease: focusing on immunopathophysiology and potential therapeutic strategies

INTRODUCTION

Erectile dysfunction (ED) represents the major cause of male sexual dysfunction, which is often associated with obesity, diabetes mellitus, atherosclerotic cardiovascular disease, and cigarette smoking. Peyronie's disease is a chronic disorder associated with irreversible fibrotic damage of the tunica albuginea leading to ED, painful erection, coital disturbance, and physical and social complaints. Both conditions are characterized by chronic inflammation, oxidative stress, and significant changes in intracavernous hydrodynamics. In this scenario, oxidized lipoproteins, M1-polarized macrophages, proinflammatory cytokines (such as the tumor necrosis factor α), endothelial nitric oxide synthase, penile smooth muscle cells, and toll-like receptors represent the main triggers of the inflammatory process in ED. Phosphodiesterase-5 inhibitors are the most common treatment for ED. This treatment is used intermittently, as it is conceived as a symptomatic and not curative therapy. Moreover, not all patients respond to phosphodiesterase-5 inhibitors (35%-85%), particularly those with dysmetabolic phenotypes. Additional or alternative treatments are therefore desirable, mostly in refractory cases.

OBJECTIVES

In this review, we describe the immune-mediated pathogenesis of ED and Peyronie's disease (PD). In our literature search we placed particular emphasis on potentially practical therapeutic approaches, including natural products (such as polyphenols), due to their anti-inflammatory and antioxidant activities, stem cell therapy, and platelet-derived preparations.

METHODS

We searched PubMed/MEDLINE, Web of Science, Scopus, Cochrane Library, Google Scholar, and institutional websites. Original studies, narrative reviews, systematic reviews, and meta-analyses written in English were searched, screened, and selected.

RESULTS

In animal models of ED and PD, therapeutic approaches, including anti-inflammatory and antioxidant agents, stem cell therapy, and platelet-derived preparations, have provided positive results, including improved penile function, reduced inflammation and oxidative stress, and promotion of tissue repair. However, clinical evidence of improvement in human patients is still insufficient.

CONCLUSION

Promising results for treating ED and PD have been shown in preclinical and pilot clinical studies, but specific clinical trials are needed to validate the efficacy of these therapeutic approaches in men with ED.

Excessive hypercholesterolemia in pregnancy impairs rat uterine artery function via activation of Toll-like receptor 4

Hypercholesterolemia in pregnancy is a physiological process required for normal fetal development. In contrast, excessive pregnancy-specific hypercholesterolemia increases the risk of complications, such as preeclampsia. However, the underlying mechanisms are unclear. Toll-like receptor 4 (TLR4) is a membrane receptor modulated by high cholesterol levels, leading to endothelial dysfunction; but whether excessive hypercholesterolemia in pregnancy activates TLR4 is not known. We hypothesized that a high cholesterol diet (HCD) during pregnancy increases TLR4 activity in uterine arteries, leading to uterine artery dysfunction. Sprague Dawley rats were fed a control diet (n=12) or HCD (n=12) during pregnancy (gestational day 6-20). Vascular function was assessed in main uterine arteries using wire myography (vasodilation to methacholine and vasoconstriction to phenylephrine; with and without inhibitors for mechanistic pathways) and pressure myography (biomechanical properties). Exposure to a HCD during pregnancy increased maternal blood pressure, induced proteinuria, and reduced the fetal-to-placental weight ratio for both sexes. Excessive hypercholesterolemia in pregnancy also impaired vasodilation to methacholine in uterine arteries, whereby at higher doses, methacholine caused vasoconstriction instead of vasodilation in only the HCD group, which was prevented by inhibition of TLR4 or prostaglandin H synthase 1. Endothelial nitric oxide synthase expression and nitric oxide levels were reduced in HCD compared with control dams. Vasoconstriction to phenylephrine and biomechanical properties were similar between groups. In summary, excessive hypercholesterolemia in pregnancy impairs uterine artery function, with TLR4 activation as a key mechanism. Thus, TLR4 may be a target for therapy development to prevent adverse perinatal outcomes in complicated pregnancies.

Deletion of toll-like receptor 4 ameliorates diabetic retinopathy in mice

BACKGROUND

Diabetic retinopathy is a common and specific microvascular complication of diabetes, which is also the leading cause of preventable blindness. Therefore, we aimed to find a promising therapeutic strategy for diabetic retinopathy.

METHODS

To investigate the role of toll-like receptor 4 (TLR4) in the diabetic retinopathy, we injected streptozotocin (STZ) into wild-type (wt) and TLR4 knock-out mice to induce diabetes.

RESULTS

While STZ induced diabetes both in wt and TLR4^-/- mice, deletion of TLR4 in diabetic mice significantly improved diabetic retinopathy compared to diabetic wt mice, as judged by the enhanced thickness of retinal tissue. Furthermore, TLR4-dependent NF-κB pathway, inflammatory cytokine release and the expressions of vascular endothelial growth factor (VEGF) and glial fibrillary acidic protein (GFAP), which were all remarkably stimulated in STZ-injected wt mice, were inhibited in STZ-injected TLR4^-/- mice.

CONCLUSION

TLR4 could serve as an independent target for treating diabetic retinopathy.

Current status and prospects of diabetes mellitus induced erectile dysfunction: A bibliometric and visualization study

BACKGROUND

The prevalence of diabetes mellitus-induced erectile dysfunction (DMED) has recently increased, which has prompted numerous DMED studies. Here, we conduct a bibliometric analysis of relevant literature in the field of DMED and to discuss the research hotspots and future development directions.

METHODS

The Web of Science Core Collection database was searched for literature on DMED, and literature characterization including the number of articles, journals, countries/regions, institutions, authors, keywords, and other information was performed using VOS viewer and CiteSpace software. In addition, Pajek software was used for visual map adjustment, and GraphPad Prism was used to generate line graphs.

RESULTS

A total of 804 articles concerning DMED were included in this study. The Journal of Sexual Medicine issued the most documents(92 articles). The United States and China were in the leading position in the field of DMED research, and cross-institutional collaboration on DMED research worldwide needs to be further strengthened. Ryu JK were the authors with the highest number of documents issued (22 articles) while Bivalacqua TJ was the author with the most co-citated(249 co-citated). The keywords analysis shows that the main research hotspots in the field of DMED were mechanism discussions and disease treatment and management.

CONCLUSIONS

Global research on DMED is expected to increase further. The investigation of the mechanism of DMED and the exploration of new therapeutic means and targets are the focus of future research.

New insights into the role and therapeutic potential of HSP70 in diabetes

Emerging evidence indicates that HSP70 represents a key mechanism in the pathophysiology of β-cell dysfunction, insulin resistance, and various diabetic complications, including micro- and macro-vascular alterations, as well as impaired hemostasis. Hyperglycemia, a hallmark of both types of diabetes, increases the circulating levels of HSP70 (eHSP70), but there is still divergence about whether diabetes up- or down-regulates the intracellular fraction of this protein (iHSP70). Here, we consider that iHSP70 levels reduce in diabetic arterial structures and that the vascular system is in direct contact with all other systems in the body suggesting that a systemic response might also be happening for iHSP70, which is characterized by decreased levels of HSP70 in the vasculature. Furthermore, although many pathways have been proposed to explain HSP70's functions in diabetes, and organs/tissues/cells-specific variations occur, the membrane-bound receptor of the innate immune system, Toll-like receptor 4, and its downstream signal transduction pathways appear to be a constant, not only when we explore the actions of eHSP70, but also when we assess the contributions of iHSP70. In this review, we focus on discussing the multiple roles of HSP70 across organs/tissues/cells affected by hyperglycemia to further explore the possibility of targeting this protein with pharmacological and non-pharmacological approaches in the context of diabetes.

Ipidacrine (Axamon), A Reversible Cholinesterase Inhibitor, Improves Erectile Function in Male Rats With Diabetes Mellitus-Induced Erectile Dysfunction

Background

Management of diabetes mellitus-induced erectile dysfunction (DMED) is challenging because of its insufficient responses to phosphodiesterase type 5 inhibitors.

Aim

To compare the effects of ipidacrine, a reversible cholinesterase inhibitor, and sildenafil on DMED in a rat model of streptozotocin (STZ)-induced diabetes.

Methods

Erectile dysfunction (ED) caused by STZ-induced diabetes mellitus was modeled in adult male Wistar rats, which were randomized to 4 groups: untreated diabetic rats, sildenafil (5 mg/kg), ipidacrine (3.6 mg/kg) and ipidacrine (6.7 mg/kg). The test drug (ipidacrine), comparator (sildenafil) or control substance (1% starch solution) were administered orally for 5 days or 14 days. Erectile function was assessed by the change in the maximum intracavernous pressure (ICPmax) following cavernous nerve electrical stimulation. The mean arterial pressure (MAP) was recorded, and the ICPmax/MAP ratio was calculated. Sexual behavior, cholinesterase activity and blood testosterone level tests assessed.

Main Outcome Measure

The quantitative value of ICPmax/MAP 14 days after the start of administration of the test drug and the comparison drug.

Results

Animals with STZ-induced diabetes mellitus showed a significant decrease in ICPmax and ICPmax/MAP ratio compared to the intact control group. When ipidacrine was administered to rats with DMED for 14 days, an increase in these indicators was noted. It was proved that ipidacrine at a dose of 6.7 mg/kg has noninferiority compared to sildenafil on the DMED model. Significant increase in ICPmax compared to STZ-control after electrostimulation of the cavernous nerve was recorded following administration of ipidacrine at a dose of 6.7 mg/kg (P < .05) and sildenafil at a dose 5 mg/kg (P < .05). Neither the test drug, nor the comparator were associated with increase in testosterone levels in blood; as well both drugs did not promote activation of sexual behavior.

Clinical Implications

Ipidacrine may be considered as an effective therapy for DMED but needs to be verified in human investigations.

Strengths & Limitations

The role of ipidacrine, was firstly demonstrated in rats with DMED. However, the results were obtained in animal experiments, and will be further tested in the study of receptor interactions and the determination of cellular targets.

Conclusion

This is the first study to show that administration of ipidacrine, the reversible cholinesterase inhibitor, improved erectile function in diabetic rats and these results may be beneficial in further studies using ipidacrine for treatment of DMED, particularly in non-responders to PDE5 inhibitors.

Bykov V, Gushchina E, Morozov S, et al. Ipidacrine (Axamon), A Reversible Cholinesterase Inhibitor, Improves Erectile Function in Male Rats With Diabetes Mellitus-Induced Erectile Dysfunction. Sex Med 2022;10:100477.

Toll-Like Receptors (TLRs) in Health and Disease: An Overview

Toll-like receptors were discovered as proteins playing a crucial role in the dorsoventral patterning during embryonic development in the Drosophila melanogaster (D. melanogaster) almost 40 years ago. Subsequently, further research also showed a role of the Toll protein or Toll receptor in the recognition of Gram-positive bacterial and fungal pathogens infecting D. melanogaster. In 1997, the human homolog was reported and the receptor was named the Toll-like receptor 4 (TLR4) that recognizes lipopolysaccharide (LPS) of the Gram-negative bacteria as a pathogen-associated molecular pattern (PAMP). Identification of TLR4 in humans filled the long existing gap in the field of infection and immunity, addressing the mystery surrounding the recognition of foreign pathogens/microbes by the immune system. It is now known that mammals (mice and humans) express 13 different TLRs that are expressed on the outer cell membrane or intracellularly, and which recognize different PAMPs or microbe-associated molecular patterns (MAMPs) and death/damage-associated molecular patterns (DAMPs) to initiate the protective immune response. However, their dysregulation generates profound and prolonged pro-inflammatory immune responses responsible for different inflammatory and immune-mediated diseases. This chapter provides an overview of TLRs in the control of the immune response, their association with different diseases, including TLR single nucleotide polymorphisms (SNPs), interactions with microRNAs (miRs), use in drug development and vaccine design, and expansion in neurosciences to include pain, addiction, metabolism, reproduction, and wound healing.

Bibliometric and visualization analysis of literature relating to diabetic erectile dysfunction

INTRODUCTION

Diabetic erectile dysfunction (DMED) refers to erectile dysfunction secondary to diabetes. Erectile dysfunction is characterized by a persistent inability to achieve and maintain an erection sufficient to permit satisfactory sexual activity.

METHODS

Based on the Web of Science core collection database, we firstly analyzed the quantity and quality of publications in the field of DMED, secondly profiled the publishing groups in terms of country, institution, author's publication and cooperation network, and finally sorted out and summarized the hot topics of research.

RESULTS

From 2001 to 2022, a total of 1,403 articles relating to this topic were published in 359 journals. They represent the global research status, potential hotspots, and future research directions. The number of DMED-related publications and citations has steadily increased over the few past decades. Academic institutions from Europe and the United States have played a leading role in DMED research. The country, institution, journal, and author with the most publications were the United States (294), INHA University (39), the Journal of Sexual Medicine (156), and Ryu, Ji-Kan (29), respectively. The most common keywords were erectile dysfunction (796), men (256), diabetes (254), diabetes mellitus (239), prevalence (180), corpus cavernosum (171), dysfunction (155), mellitus (154), nitric-oxide synthase (153), and expression (140). The main keyword-based research topics and hotspots in the DMED field were oral sildenafil, smooth muscle relaxation, nitric oxide synthase, gene therapy, metabolic syndrome, cavernous nerve injury, stem cell, and penile prosthesis.

DISCUSSION

The terms oral sildenafil, smooth muscle relaxation, nitric oxide synthase, gene therapy, metabolic syndrome, cavernous nerve injury, stem cell, and penile prosthesis will be at the forefront of DMED-related research.

Chrysin ameliorates STZ-induced diabetes in rats: possible impact of modulation of TLR4/NF-κβ pathway

Background and purpose:

Growing evidence advocates that upregulation of toll-like receptor 4 (TLR4) has been suggested as a causative influence in the development and complications of diabetes mellitus. We aimed to study the antidiabetic activity of chrysin against streptozotocin (STZ)-induced diabetes via down-regulation of TLR4/nuclear factor (NF-κβ)/heat shock protein 70 (HSP70) pathway as well as modulation of clusters of differentiation 4 (CD4+) in rats.

Experimental approach:

Fifty rats were divided into five groups (n = 10). Group I, normal rats received a single intraperitoneal injection of buffer citrate; group II, STZ-induced diabetic rats; groups III-V, diabetic rats received glimepiride (0.5 mg/kg; p.o.) or chrysin (40 and 80 mg/kg; p.o.) respectively, for 10 days. Serum samples were extracted to determine nitric oxide (NO), malondialdehyde (MDA), and reduced glutathione (GSH), insulin, CD4+, TLR4, and NF-κβ. Pancreatic tissue samples were extracted to determine glucose transporter 2 (GLUT2). Part of the pancreas was kept in formalin for pathological studies.

Findings/Results:

An elevation in blood glucose, NO, and MDA serum levels and a reduction of pancreatic GLUT2 content, insulin, and GSH serum levels were observed in diabetic rats. STZ injection, also, showed an increase in serum TLR4, NF-κβ, and HSP70 levels and a reduction in serum CD4+ levels with pancreatic cells necrosis. These biochemical and histological changes were reversed in glimepiride and chrysin groups.

Conclusion and implications:

The present study proved that chrysin has a potent anti-diabetic effect through the elevation of insulin and GLUT2 levels, the reduction of oxidative stress, and the inflammatory pathways TLR4/NF-κβ/HSP70 with the regulation of CD4+.

Inhibition of inducible nitric oxide synthase improved erectile dysfunction in rats with type 1 diabetes

Diabetes mellitus (DM), which is closely related to microvascular dysfunction, is a risk factor for erectile dysfunction (ED). Furthermore, the upregulation of inducible nitric oxide synthase (iNOS) is associated with systemic vascular dysfunction in rats with diabetes. The purpose of this study was to investigate the role of iNOS in diabetes mellitus erectile dysfunction (DMED). First, we developed a type 1 DM rat model using streptozotocin and selected those that developed DMED. Then, we injected these rats with the 1400W, an iNOS inhibitor, for 10 weeks and subsequently assessed their ED. Lastly, we performed various molecular studies and histopathological analyses of penile tissues collected from these rats after the experiments. Through the histopathological studies, we also found that the treatment restored the ratios of the smooth muscle to collagen fibres, delayed the development of microvascular injury and alleviated the oxidative stress caused by hyperglycaemia. Based on these results, we confirmed that upregulation of iNOS leads to microvascular dysfunction in patients with ED. Overall, we found that inhibition of iNOS displayed beneficial effects in the treatment of ED, suggesting that its mechanism should be further explored.

Crosstalk of TLR4, vascular NADPH oxidase, and COVID-19 in diabetes: What are the potential implications?

Toll-like receptor 4 (TLR4) contributes to the pathophysiology of diabetes. This happens, at least in part, because TLR4 modulates the enzyme NADPH oxidase, a primary source of ROS in vascular structures. Increased oxidative stress disrupts key vascular signaling mechanisms and drives the progression of diabetes, elevating the likelihood of cardiovascular diseases. Recently, it has been shown that patients with diabetes are also at a higher risk of developing severe coronavirus disease 2019 (COVID-19). Given the importance of the interaction between TLR4 and NADPH oxidase to the disrupted diabetic vascular system, we put forward the hypothesis that TLR4-mediated NADPH oxidase-derived ROS might be a critical mechanism to help explain why this disparity appears in diabetic patients, but unfortunately, conclusive experimental evidence still lacks in the literature. Herein, we focus on discussing the pathological implications of this signaling communication in the diabetic vasculature and exploring this crosstalk in the context of diabetes-associated severe COVID-19.

Macrophage-Specific Toll Like Receptor 9 (TLR9) Causes Corpus Cavernosum Dysfunction in Mice Fed a High Fat Diet

BACKGROUND

Erectile dysfunction (ED) has been shown to be related with inflammatory markers in humans. Chronic infusion of TNF-α caused ED in mice while TNF-α knockout mice exhibited improvement in the relaxation of the corpus cavernosum (CC).

AIM

Since obesity triggers an inflammatory process, we aimed to investigate the hypothesis that in obesity, Toll-like receptor 9 (TLR9) activation leads to increased TNF-α levels and impairment in CC reactivity.

METHODS

Four-week old male C57BL6 (WT) and TLR9 mutant (TLR9_MUT) mice were fed a standard chow or high fat diet (HFD) for 12 weeks. Body weight and nonfasting blood glucose were analyzed. Contractile and relaxation responses of the CC were evaluated by electrical field stimulation and concentration response curves to phenylephrine and acetylcholine. Protein expression of nNOS, TNF-α, TNF-R1, TLR9 and MyD88 were measured by western blot. Plasma levels of TNF-α were measured by ELISA.

OUTCOME

In obesity, impaired cavernosal relaxation is associated with the activation of the innate immune system, by increasing the production of TNF-α through the activation of TLR9 in the macrophages.

RESULTS

After 12 weeks of HFD both WT and TLR9_MUT mice had increased body weight and nonfasting blood glucose compared to standard chow. In the CC, acetylcholine-induced relaxation was not changed. A trend to increased contraction to phenylephrine and KCl was seen in WT HFD only. electrical field stimulation-induced relaxation of the CC was decreased in WT HFD as well as nNOS expression in the CC of WT HFD, but not in TLR9_MUT HFD. In the CC, protein expression of TLR9 and MyD88 was similar in all groups. While circulating levels of TNF-α presented only a trend to increase in mice fed HFD, the CC expression of TNF-α was increased only in WT HFD mice.

CLINICAL TRANSLATION

The innate immune system can be a target for the treatment of erectile complications in obesity.

STRENGTHS AND LIMITATIONS

This is the first study demonstrating that activation of TLR9 expressed in macrophages leads to impaired cavernosal relaxation. The main limitation of the study is the lack of understanding about the source/expression of the macrophages in the cavernous tissue. Further, herein, the experiments were performed only in isolated cavernous tissue (in vitro), thus the lack of knowledge on how the TLR9 modulates the in vivo response of the erectile tissue is another limitation of this study.

CONCLUSION

Our findings indicate that CC dysfunction observed in obesity is at least in part mediated by the production of TNF-α upon activation of TLR9 expressed in the macrophages. Priviero F, Calmasini F, Dela Justina V, et al. Macrophage-Specific Toll Like Receptor 9 (TLR9) Causes Corpus Cavernosum Dysfunction in Mice Fed a High Fat Diet. J Sex Med 2021;18:723-731.

Hypertension and Erectile Dysfunction: Breaking Down the Challenges

A diagnostic of hypertension increases the risk of erectile dysfunction (ED); likewise, ED can be an early sign of hypertension. In both cases, there is evidence that endothelial dysfunction is a common link between the 2 conditions. During hypertension, the sustained and widespread release of procontractile factors (e.g., angiotensin II, endothelin 1, and aldosterone) impairs the balance between vasoconstrictors and vasodilators and, in turn, detrimentally impacts vascular and erectile structures. This prohypertensive state associates with an enhancement in the generation of reactive oxygen species, which is not compensated by internal antioxidant mechanisms. Recently, the innate immune system, mainly via Toll-like receptor 4, has also been shown to actively contribute to the pathophysiology of hypertension and ED not only by inducing oxidative stress but also by sustaining a low-grade inflammatory state. Furthermore, some drugs used to treat hypertension can cause ED and, consequently, reduce compliance with the prescribed pharmacotherapy. To break down these challenges, in this review, we focus on discussing the well-established as well as the emerging mechanisms linking hypertension and ED with an emphasis on the signaling network of the vasculature and corpora cavernosa, the vascular-like structure of the penis.

Application of Animal Models in Diabetic Cardiomyopathy

Diabetic heart disease is a growing and important public health risk. Apart from the risk of coronary artery disease or hypertension, diabetes mellitus (DM) is a well-known risk factor for heart failure in the form of diabetic cardiomyopathy (DiaCM). Currently, DiaCM is defined as myocardial dysfunction in patients with DM in the absence of coronary artery disease and hypertension. The underlying pathomechanism of DiaCM is partially understood, but accumulating evidence suggests that metabolic derangements, oxidative stress, increased myocardial fibrosis and hypertrophy, inflammation, enhanced apoptosis, impaired intracellular calcium handling, activation of the renin-angiotensin-aldosterone system, mitochondrial dysfunction, and dysregulation of microRNAs, among other factors, are involved. Numerous animal models have been used to investigate the pathomechanisms of DiaCM. Despite some limitations, animal models for DiaCM have greatly advanced our understanding of pathomechanisms and have helped in the development of successful disease management strategies. In this review, we summarize the current pathomechanisms of DiaCM and provide animal models for DiaCM according to its pathomechanisms, which may contribute to broadening our understanding of the underlying mechanisms and facilitating the identification of possible new therapeutic targets.

New insights into RhoA/Rho-kinase signaling: a key regulator of vascular contraction

While Rho-signalling controlling vascular contraction is a canonical mechanism, with the modern approaches used in research, we are advancing our understanding and details into this pathway are often uncovered. RhoA-mediated Rho-kinase is the major regulator of vascular smooth muscle cells and a key player manoeuvring other functions in these cells. The discovery of new interactions, such as oxidative stress and hydrogen sulphide with Rho signalling are emerging addition not only in the physiology of the smooth muscle, but especially in the pathophysiology of vascular diseases. Likewise, the interplay between ageing and Rho-kinase in the vasculature has been recently considered. Importantly, in smooth muscle contraction, this pathway may also be affected by sex hormones, and consequently, sex-differences. This review provides an overview of Rho signalling mediating vascular contraction and focuses on recent topics discussed in the literature affecting this pathway such as ageing, sex differences and oxidative stress.

Mechanisms of diabetic cardiomyopathy and potential therapeutic strategies: preclinical and clinical evidence

The pathogenesis and clinical features of diabetic cardiomyopathy have been well-studied in the past decade, but effective approaches to prevent and treat this disease are limited. Diabetic cardiomyopathy occurs as a result of the dysregulated glucose and lipid metabolism associated with diabetes mellitus, which leads to increased oxidative stress and the activation of multiple inflammatory pathways that mediate cellular and extracellular injury, pathological cardiac remodelling, and diastolic and systolic dysfunction. Preclinical studies in animal models of diabetes have identified multiple intracellular pathways involved in the pathogenesis of diabetic cardiomyopathy and potential cardioprotective strategies to prevent and treat the disease, including antifibrotic agents, anti-inflammatory agents and antioxidants. Some of these interventions have been tested in clinical trials and have shown favourable initial results. In this Review, we discuss the mechanisms underlying the development of diabetic cardiomyopathy and heart failure in type 1 and type 2 diabetes mellitus, and we summarize the evidence from preclinical and clinical studies that might provide guidance for the development of targeted strategies. We also highlight some of the novel pharmacological therapeutic strategies for the treatment and prevention of diabetic cardiomyopathy.

Blockade of the TLR4-MD2 complex lowers blood pressure and improves vascular function in a murine model of type 1 diabetes

While the pathogenesis of diabetes-induced high blood pressure (BP) is not entirely clear, current evidence suggests that Toll-like receptor 4 (TLR4) is a key player in the mechanisms associated with hypertension. However, it is unknown whether this receptor affects BP under type 1 diabetes. Likewise, there is insufficient knowledge about the role of TLR4 in diabetes-associated vascular dysfunction of large arteries. To narrow these gaps, in this study, we investigated if blockade of the TLR4-MD2 complex impacts BP and vascular function in diabetic rats. We injected streptozotocin in male Sprague Dawley rats and treated them with a neutralizing anti-TLR4 antibody for 14 days. BP was directly measured in conscious animals at the end of the treatment. In another set of experiments, we excised the aorta from control and diabetic animals, and measured TLR4 and MD2—a co-receptor that confers functionality to TLR4—levels by Western blotting. We also performed functional studies and evaluated ROS levels with and without a pharmacological inhibitor for TLR4 as well as for MD2. Additionally, we scrutinized a large human RNA-Seq dataset of aortic tissue to assess the co-expression of TLR4, MD2, and subunits of the vascular NADPH oxidases under diabetes and hypertension. We report that (a) chronic blockade of the TLR4–MD2 complex lowers BP in diabetic animals; that (b) type 1 diabetes modulates the levels of MD2 expression in the aorta, but not TLR4, at least in the conditions evaluated in this study; and, that (c) acute inhibition of TLR4 or MD2 diminishes vascular contractility and reduces oxidative stress in the aorta of these animals. In summary, we show evidence that the TLR4–MD2 complex is involved in the mechanisms linking type 1 diabetes and hypertension.

Combined treatment with extracorporeal shockwaves therapy and an herbal formulation for activation of penile progenitor cells and antioxidant activity in diabetic erectile dysfunction

Background

A Korean herbal formulation named KH-204 was reported to have an antioxidant effect in our previous study. We hypothesized that Low-intensity extracorporeal shockwave therapy (Li-ESWT) combined with KH-204 would accelerate the treatment of erectile dysfunction (ED) by enhancing antioxidant. We investigated the synergistic effect of Li-ESWT and KH-204 for ED and explored the mechanism.

Methods

Human umbilical vein endothelial cells (HUVEC) were treated with KH-204 and LI-ESWT in vitro. Fifty 5-week-old male Sprague Dawley rats received an intraperitoneal injection of 5-ethynyl-20-deoxyuridine (EdU) which can label live cells, and were randomly divided into five groups: (I) normal; (II) diabetes mellitus-associated erectile dysfunction (DMED); (III) DMED + KH-204; (IV) DMED + Li-ESWT; and (V) DMED + KH-204/Li-ESWT. Li-ESWT treatment was repeated three times a week every other day for four weeks in group 4 and 5. Meanwhile, rats in group 3 and 5 were orally fed 400 mg/kg of KH-204 daily for 1 month. Following a 1-week washout period, penile tissues were evaluated by immunostaining and Western blotting.

Results

KH-204 combined with Li-ESWT improved intracavernosal pressure (ICP) in DMED rats. Li-ESWT/KH-204 stimulated HUVEC tube formation and promoted proliferation. Li-ESWT drove progenitor cells to migrate to penile tissue and KH-204 protected penile progenitor cells in the corpus cavernosum. Oxidative stress was relieved by KH-204/Li-ESWT. Treatment with KH-204/Li-ESWT protected penile progenitor cells, which were recruited to the corpus cavernosum by Li-ESWT, from apoptosis via its antioxidant activity. KH-204/Li-ESWT protected penile tissue from oxidative stress by improving the expression of nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1), increasing superoxide dismutase (SOD), decreasing 8-hydroxy-20-deoxyguanosine (8-OHdG), and reducing apoptosis. KH-204/Li-ESWT promoted stromal derived factor-1 (SDF-1) and platelet endothelial cell adhesion molecule-1 (PECAM-1) in DMED rats.

Conclusions

KH-204 protected penile progenitor cells, which were recruited to the corpus cavernosum by Li-ESWT, from apoptosis via its antioxidant activity. The combination of Li-ESWT and KH-204 as a synergy therapy could be a potential and effective treatment for DMED.

Toll-Like Receptor 4 and Heat-Shock Protein 70: Is it a New Target Pathway for Diabetic Vasculopathies?

Diabetes is one of the most concerning diseases in modern times. Despite considerable advances in therapeutic management, the prevalence of diabetes and its contribution to death and disability continue to be a major health problem. Diabetic vasculopathies are the leading cause of mortality and morbidity in diabetic patients. Its pathophysiology includes oxidative stress, advanced glycation end products, and a low-grade inflammatory state. Lately, actions of the innate immune system via Toll-like receptors (TLRs) have been suggested as a new insight in this field. TLRs are pattern recognition receptors activated by highly conserved structural motifs of exogenous or endogenous ligands. Heat-shock proteins (HSPs), normally known for their ability to protect cells during stressful conditions, when released from injured cells bind to TLR4 and trigger the release of pro-inflammatory cytokines in a MyD88-dependent pathway. This pathway had been investigated in pancreatic beta cells and skeletal muscle, but it has not yet been explored in the vascular system and deserves investigation. In this work, the interplay between TLR4 and HSP70 in the vasculature during diabetes is reviewed and discussed. The current literature and preliminary results from our laboratory led us to hypothesize that hyperglycemia-associated HSP70 plays an important role in the pathophysiology of diabetic vasculopathies via the TLR4 pathway and might be a new target for therapeutic intervention.

Tlr1-13, Nod1/2 and antimicrobial gene expression in the epididymis and testis of rats with alloxan-induced diabetes

Pattern recognition receptors (PRRs) such as toll-like receptors (TLRs) and nuclear oligomerization domain (NOD) receptors along with antimicrobial proteins and peptides (AMPs) are crucial for innate immunity. The pathology of insulin-dependent diabetes mellitus is associated with the disrupted expression of TLRs, NODs and AMPs in the kidney, lungs and other organs. However, such a relation in the male reproductive tract is not yet investigated. In this study, we analysed the expression pattern of Tlr1-13, Nod1/2 receptors and AMPs (β-defensins and defensin-like proteins of the Sperm-Associated Antigen 11 (Spag11) family) in the male reproductive tissues (caput, cauda and testis) obtained from diabetic or insulin-treated diabetic or untreated control rats. Alterations in the expression pattern of Tlr1-13, Nod 1/ 2, Defb1, 2, 21, 24, 27, 30 and Spag11a/ c/ t were observed under diabetic conditions. Administration of insulin to diabetic rats could modulate the expression pattern of only some these genes. Results of our study indicate perturbed gene expression profile of Tlrs, Nod1/2, Defbs and Spag11 isoforms in the epididymis and testis of diabetic rats, and this could be one of the important reasons for the increased risk of infections in the male genital tract.

Unveiling the Interplay between the TLR4/MD2 Complex and HSP70 in the Human Cardiovascular System: A Computational Approach

While precise mechanisms underlying cardiovascular diseases (CVDs) are still not fully understood, previous studies suggest that the innate immune system, through Toll-like receptor 4 (TLR4), plays a crucial part in the pathways leading to these diseases, mainly because of its interplay with endogenous molecules. The Heat-shock protein 70 family (HSP70-70kDa) is of particular interest in cardiovascular tissues as it may have dual effects when interacting with TLR4 pathways. Although the hypothesis of the HSP70 family members acting as TLR4 ligands is becoming widely accepted, to date no co-crystal structure of this complex is available and it is still unknown whether this process requires the co-adaptor MD2. In this study, we aimed at investigating the interplay between the TLR4/MD2 complex and HSP70 family members in the human cardiovascular system through transcriptomic data analysis and at proposing a putative interaction model between these proteins. We report compelling evidence of correlated expression levels between TLR4 and MD2 with HSP70 cognate family members, especially in heart tissue. In our molecular docking simulations, we found that HSP70 in the ATP-bound state presents a better docking score towards the TLR4/MD2 complex compared to the ADP-bound state (-22.60 vs. -10.29 kcal/mol, respectively). Additionally, we show via a proximity ligation assay for HSP70 and TLR4, that cells stimulated with ATP have higher formation of fluorescent spots and that MD2 might be required for the complexation of these proteins. The insights provided by our computational approach are potential scaffolds for future in vivo studies investigating the interplay between the TLR4/MD2 complex and HSP70 family members in the cardiovascular system.

Overexpression of Sirt6 promotes M2 macrophage transformation, alleviating renal injury in diabetic nephropathy

In this study, we aimed to investigate the associations between Sirt6, macrophages and diabetic nephropathy (DN). Immunohistochemical, western blot and RT-qPCR analyses were performed to detect the expression levels of Sirt6, the markers of podocytes and monocytes and related inflammatory factors in the tissues of rats with streptozocin-induced DN. A series of cell experiments in isolated culture or the co-culture of macrophages and podocytes were conducted to examine the effects of the overexpression of Sirt6 on macrophage transformation, podocyte apoptosis and associated genes, and analyses were performed using RT-qPCR, flow cytometry and western blot analysis, where appropriate. In the rat model of DN, injured podocytes were represented by the decreased protein expression levels of Nephrin and Sirt6, and by an increased Desmin expression. Additionally, the M1 phenotype transformation of macrophages was evidenced by the increased expression levels of CD86, tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS), and by the decreased expression levels of CD206, Sirt6, interleukin (IL)-4 and IL-10. In vitro assays of macrophages and podocytes demonstrated that glucose promoted macrophage M1 transformation and podocyte apoptosis in a dose-dependent manner and attenuated Sirt6 expression. Macrophages transformed into the M2 phenotype following the overexpression of Sirt6 by the successful transfection of macrophages with a Sirt6 overexpression plasmid. Sirt6 was also overexpressed in podocytes. In a Transwell co-culture system, the overexpression of Sirt6 in macrophages (but not the overexpression of Sirt6 in podocytes) protected the podocytes from high-glucose-induced injury. However, the apoptosis of the podocytes overexpressing Sirt6 (induced by transfection with a Sirt6 overexpression plasmid) still increased when these podocytes were co-cultured with macrophages in high-glucose medium. These protective effects were evidenced by the inhibition of apoptosis, the upregulation of the expression levels of Bcl-2 and CD206, as well as by the decreased expression levels of Bax and CD86. On the whole, the findings of this study suggest that Sirt6 protects podocytes against injury in a mimicked diabetic kidney microenvironment by activating M2 macrophages, indicating that Sirt6 can act as an immune response regulatory factor in DN-associated renal inflammatory injury.