Calcium dobesilate attenuates vascular injury and the progression of diabetic retinopathy in streptozotocin-induced diabetic rats

Exploration of the mechanisms underlying the beneficial effect of Luo Tong formula on retinal function in diabetic rats via the "gut microbiota-inflammation-retina" axis

BACKGROUND

Diabetic retinopathy (DR) is a common microvascular complication of diabetes. Luo Tong formula (LTF), a classical traditional Chinese medicine (TCM) prescription, consists of four plants that have been widely and effectively used to treat DR. Previous work in our laboratory has confirmed that LTF can effectively ameliorate DR. However, the potential mechanism underlying the therapeutic effect of LTF on DR has not been fully elucidated. To explore the potential mechanism of action through which LTF prevents and alleviates DR from an inflammation and gut microbiota perspective.

MATERIALS AND METHODS

Metabolite profiling of LTF was performed using liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS). Type 1 diabetes was induced in male Sprague Dawley (SD) rats via tail vein injection of 45 mg/kg streptozotocin. Next, 100 SD rats were randomly divided into four groups, normal control; diabetic control; diabetic + insulin + calcium dobesilate; and diabetic + insulin + LTF. After 12 weeks of treatment, glucose metabolism, fundus oculi, blood-retinal barrier permeability, retinal thickness, microvascular damage, as well as cell junction expression in retinas were measured and the changes observed in different groups were compared. Finally, the alteration in gut microbiota and inflammatory cytokine expression in serum and tissues were monitored, and their correlation was analyzed.

RESULTS

A total of 1024 valid peaks were obtained for LTF using GC-MS. The HbA1c and fasting blood glucose (FBG) levels in the LTF group were slightly decreased. LTF exerted protective effects on fundus oculi and the retina structure to different degrees. LTF attenuated systemic and local retinal inflammation by significantly decreasing the levels of seven pro-inflammatory cytokines, including ICAM-1, IL-6, IL-8, MCP-1, VCAM-1, VEGF, and IL-1β. LTF restored the intestinal microbiota of diabetic rats to levels that were similar to those of normal rats. Further analysis revealed that Enterobacteriales, Prevotellaceae, Enterobacteriaceae, Bacteroides, and Klebsiella were significantly and positively correlated with the inflammatory factors in DR after LTF treatment.

CONCLUSIONS

Our results revealed the mechanisms underlying the preventive effects of LTF on DR development and progression. LTF inhibited pathological changes in retinal histopathology, cell composition, and cell junction proteins while effectively ameliorating systemic and local retinal inflammation via regulating pivotal gut microbiota.

Calcium dobesilate alleviates renal dysfunction and inflammation by targeting nuclear factor kappa B (NF-κB) signaling in sepsis-associated acute kidney injury

Acute kidney injury (AKI) is a serious complication of sepsis that increases mortality and the risk of progression to chronic kidney disease. Oxidative stress and apoptosis are reported to exert critical function in the pathogenesis of sepsis-associated AKI. Calcium dobesilate (CaD) was reported to play a protective role in renal diseases. Therefore, we explored the antioxidant effect and potential mechanism of CaD in lipopolysaccharide (LPS)-induced AKI in mice. We evaluated renal function (blood urea nitrogen (BUN) and serum creatinine (SCr)), histopathology, oxidative stress (superoxide dismutase (SOD) and malondialdehyde (MDA)), inflammation cytokines, and apoptosis in kidneys of mice. The effect of CaD on NF-κB signaling was evaluated by Western blot. Our findings showed that CaD alleviated renal dysfunction and kidney injury, and also reversed upregulated MDA concentration and reduced SOD enzyme activity in AKI mice. Moreover, LPS-induced inflammatory response was attenuated by CaD. CaD treatment also reduced the apoptosis evoked by LPS. Additionally, CaD downregulated phosphorylation of nuclear factor kappa B (NF-κB) signaling components in LPS mice. Conclusively, CaD alleviates renal dysfunction and inflammation by targeting NF-κB signaling in sepsis-associated AKI.

Calcium dobesilate mediates renal interstitial fibrosis and delay renal peritubular capillary loss through Sirt1/p53 signaling pathway

Calcium dobesilate (Cad), a protective agent, protects against microvascular damage, and diseases such as diabetic retinopathy and diabetic nephropathy. However, these vascular protective effects have not been demonstrated in chronic kidney disease (CKD). In this study, we aimed to determine the ability of Cad to protect against renal interstitial fibrosis induced by unilateral ureteral obstruction (UUO) and identify the underlying therapeutic mechanisms of Cad during hypoxia/serum deprivation (H/SD) in human umbilical vein endothelial cells (HUVECs). A total of 36 male mice were randomly assigned into 3 groups (12 mice in each group): the Sham-operated group (Sham), the saline solution-treated UUO mice group (UUO), and the Cad administration (intragastrically) group (Cad). The mice in Cad group were administered Cad (100 mg/kg) daily by oral gavage and slaughtered on the 7th and 14th days post-surgery. Six mice from each group were sacrificed by sodium pentobarbital injection on the 7th and 14th day after surgery. Tissue hypoxia, cell apoptosis and fibrotic lesions were detected by Immunostaining and Western blot. Peritubular capillaries (PTCs) injury was measured by a novel technique of fluorescent microangiography (FMA). Endothelial cell-to-mesenchymal transition (EndMT) were identified by immunofluorescence and Western blot. HUVECs proliferation was measured via Cell Counting Kit‑8 assays and Edu staining. Sirt1 and its downstream gene in Cad regulation of endothelial were detected. Hematoxylin-eosin (HE), Masson-trichrome stains and Histological findings showed that Cad administration markedly reduced hypoxia and renal interstitial fibrosis at each time point in UUO. Meanwhile, Cad protect against EndMT process of PTCs by increasing CD31 expression and decreasing α-smooth muscle actin and fibronectin expression. in vitro studies showed that there was a proliferative response of the HUVECs incubated with Cad (10 μM) in H/SD. Sirt1 was suppressed after small interfering RNA (siRNA) was transfected in HUVECs. Mechanistically, Cad enhanced Sirt1 signaling, which was accompanied by increased levels of p53 acetylation (ac-p53). Meanwhile, protein expression of Bcl-2, and VE-cadherin were downregulated, Bax, and α-SMA were upregulated. In summary, the therapeutic effect of Cad in obstructive nephropathy were likely through suppressing EndMT progression and promoting anti-apoptotic effects after via activating the Sirt1/p53 signaling pathway.

Update on the Effects of Antioxidants on Diabetic Retinopathy: In Vitro Experiments, Animal Studies and Clinical Trials

Current therapies for diabetic retinopathy (DR) incorporate blood glucose and blood pressure control, vitrectomy, photocoagulation, and intravitreal injections of anti-vascular endothelial growth factors or corticosteroids. Nonetheless, these techniques have not been demonstrated to completely stop the evolution of this disorder. The pathophysiology of DR is not fully known, but there is more and more evidence indicating that oxidative stress is an important mechanism in the progression of DR. In this sense, antioxidants have been suggested as a possible therapy to reduce the complications of DR. In this review we aim to assemble updated information in relation to in vitro experiments, animal studies and clinical trials dealing with the effect of the antioxidants on DR.

Fabrication of resveratrol coated gold nanoparticles and investigation of their effect on diabetic retinopathy in streptozotocin induced diabetic rats

This study includes the fabrication of gold nanoparticles (AuNPs) with the help of a plant polyphenol called Resveratrol through an ecofriendly synthetic process without any use of harmful reductants. In the fabrication of AuNPs, Resveratrol acts as both stabilizing and reducing agent. The prepared AuNPs is tested on streptozotocin (STZ) induced diabetic rats for their amelioration consequence. The images of TEM displayed the development of spherical nanoparticles (NPs) with a median of 20 nm particle size. The STZ injected diabetic rats were administrated orally with calcium dobesilate (CD; 500 mg/kg/day) or AuNPs (200, 300 mg/kg/day) for a period of 3 months. The characteristics displayed by AuNPs were found to be similar with CD in decreasing permeability of blood-retinal barrier in STZ injected diabetic rats. The retinal vessels in the AuNPs administrated diabetic rats were observed to be decreased through the retinal histopathological examination. In the AuNPs administrated diabetic rats, the retinal expression of renal Pigment Epithelium-Derived Factor (PEDF) was observed to be increased and the Vascular Endothelial Growth Factor (VEGF-1), which was increased in diabetic rats was declined on treating with AuNPs. On treating the STZ injected diabetic rats with AuNPs, all the retinal mRNA expressions of VEGF-1, Tumor Necrosis Factor (TNFα), Monocyte Chemotactic Proteins-1 (MCP-1), Intercellular Adhesion Molecule-1 (ICAM-1), and Interleukin (IL)-6, IL-1β were observed to be reduced. Furthermore, AuNPs can reduce phosphorylation of Nuclear Factor Kappa B (NF-κB) p65 and Extracellular signal Regulated Kinase (ERK) 1/2 along with a growth in nuclear translocation of pNF-κB p65 produced by STZ. To conclude, the protective effect of AuNPs on STZ injected diabetic rats could help in redeveloping the balance among the inhibitors and stimulators of angiogenesis. Furthermore, on treating with AuNPs results in inhibiting the signaling pathway of ERK1/2 as well as with amelioration of retinal inflammation through trans repression of NF-κB.

Calcium Dobesilate and Micro-vascular diseases

Micro-vascular diseases and its associated complications continue to be a significant health problem worldwide. Vascular lesions from microvascular involvement lead to impaired blood flow and contribute to damage and dysfunction of one or more target organs, that is, the heart, kidneys, eyes, and nervous system. Calcium Dobesilate Drug (CAD) is an established vasoactive and angioprotective drug that has shown a unique, multitarget mode of action in several experimental studies and in different animal models of diabetic microvascular complications. CAD has been widely used as an antioxidant and a vascular protective agent. At present, the application of Calcium Dobesilate is mainly related to Micro-vascular damage-related diseases, such as diabetic retinopathy (DR) and diabetic nephropathy (DN), and it is found to significantly improve the related symptoms. Its beneficial effects make it an attractive therapeutic compound especially in the early stages of these diseases. Scholars at home and abroad have studied the effectiveness, safety, and mechanisms of the related diseases, furthermore, the subjects involved patients and animal models, they have found some new clinical effects of this medicine. This paper makes a brief summary of a research progress of clinical application about Vascular injury related diseases and other aspects.

Calcium Dobesilate Prevents Neurodegeneration and Vascular Leakage in Experimental Diabetes

PURPOSE

The mechanisms involved in the reported beneficial effects of Calcium dobesilate monohydrate (CaD) for the treatment of diabetic retinopathy (DR) remain to be elucidated. The main aim of the present study is to examine whether CaD prevents early events in the pathogenesis of DR such as neurodegeneration and vascular leakage. In addition, putative mediators of both neurodegeneration (glutamate/GLAST, ET-1/ETB receptor) and early microvascular impairment (ET-1/ETA receptor, oxidative stress, VEGF, and the PKC-delta-p38 MAPK pathway) have been examined.

METHODS

Diabetic (db/db) mice were randomly assigned to daily oral treatment with CaD (200 mg/Kg/day) (n = 12) or vehicle (n = 12) for 14 days. In addition, 12 non-diabetic (db/+) mice matched by age were used as the control group. Functional abnormalities were assessed by electroretinography. Neurodegeneration and microvascular abnormalities were evaluated by immunohistochemistry and Western blot. Glutamate was determined by HPLC.

RESULTS

CaD significantly decreased glial activation and apoptosis and produced a significant improvement in the electroretinogram parameters. Mechanistically, CaD prevented the diabetes-induced up-regulation of ET-1 and its cognate receptors (ETA-R and ETB-R), which are involved in microvascular impairment and neurodegeneration, respectively. In addition, treatment with CaD downregulated GLAST, the main glutamate transporter, and accordingly prevented the increase in glutamate. Finally, CaD prevented oxidative stress, and the upregulation of VEGF and PKC delta-p38 MAPK pathway induced by diabetes, thus resulting in a significant reduction in vascular leakage.

CONCLUSIONS

Our findings demonstrate for the first time that CaD exerts neuroprotection in an experimental model of DR. In addition, we provide first evidence that CaD prevents the overexpression of ET-1 and its receptors in the diabetic retina. These beneficial effects on the neurovascular unit could pave the way for clinical trials addressed to confirm the effectiveness of CaD in very early stages of DR.

[Modern approach to early diagnosis and pathogenetic treatment of diabetic retinopathy]

AIM

To improve the approach to pathogenetic treatment of diabetic retinopathy (DR) through early diagnosis and a new method for predicting disease progression.

MATERIAL AND METHODS

The study enrolled 330 type 2 diabetes patients with DR (660 eyes), of whom women constituted 64.6%, men - 35.4%. The mean patient age was 62.3±2.3 years. Three groups were formed: the controls - 30 healthy volunteers (60 eyes) and 30 type 2 diabetes patients without ocular involvement (DR 0, 60 eyes); group 1 - 30 type 2 diabetes patients with DR I but no diabetic macular edema (DR I without DME, 60 eyes) that were treated with calcium dobesilate; group 2 - 240 type 2 diabetes patients, who had diabetic retinopathy of different stages (DR I, II, or III with DME, 480 eyes) and received laser retinal photocoagulation (LRP). The groups were all alike in terms of sex and age distribution. All patients underwent ophthalmic examination, including best corrected visual acuity (BCVA) and critical flicker fusion frequency (CFFF) testing, tonometry, biomicroscopy, MAIA fundus microperimetry, optical coherence tomography (OCT), and fluorescein angiography (FAG) of the retina. Traditionally we also determined blood sugar and glycated hemoglobin levels as well as vascular endothelial growth factor (VEGF-A) and monocyte chemoattractant protein (MCP-1) in tear fluid by ELISA.

RESULTS

In group 1, which was under conservative therapy with calcium dobesilate, there was an increase in BCVA by the average of 0.95±0.02 and CFFF by 42.5±0.2 Hz (p<0,05). The mean central retinal thickness decreased reliably down to 265.1±12.1 µm (p<0.05). Light sensitivity of the macula improved and scored 24.13±12.3 dB (p<0.05). In group 2, the mean central retinal thickness appeared to be 383.1±221 µm, which was reliably higher than that in healthy individuals (p<0.05) and in type 2 diabetes patients without diabetic retinopathy (DR 0) (p<0.05). Tear assessment 12 months after the treatment revealed a significant decrease in VEGF-A and MCP-1 concentrations - down to 655.1±86.1 pg/ml and 1133 pg/ml, respectively (p<0.05).

CONCLUSION

Conservative treatment with calcium dobesilate has proved effective in patients with DR I without DME as it ensures improvement and stabilization of the state of the retina (clinical and morphological) in one month already (judging from FAG and OCT findings). Laser treatment is rational in DR I, DR II, and DR III patients, whose condition is complicated with DME. Improvement and stabilization take, however, longer to be achieved - up to 1 year (according to FAG and OCT). Tear fluid assessment for particular participants in disease pathogenesis, such as VEGF-A and MCP-1, is a unique method for disease control and patient follow-up with account to different treatments. A new method for predicting the progression of diabetic retinopathy and diabetic macular edema has been suggested (RF patent for invention №2520826).

Consumption of Polyphenol-Rich Zingiber Zerumbet Rhizome Extracts Protects against the Breakdown of the Blood-Retinal Barrier and Retinal Inflammation Induced by Diabetes

The present study investigates the amelioration of diabetic retinopathy (DR) by Zingiber zerumbet rhizome ethanol extracts (ZZRext) in streptozotocin-induced diabetic rats (STZ-diabetic rats). ZZRext contains high phenolic and flavonoid contents. STZ-diabetic rats were treated orally with ZZRext (200, 300 mg/kg per day) for three months. Blood-retinal barrier (BRB) breakdown and increased vascular permeability were found in diabetic rats, with downregulation of occludin, and claudin-5. ZZRext treatment effectively preserved the expression of occludin, and claudin-5, leading to less BRB breakdown and less vascular permeability. Retinal histopathological observation showed that the disarrangement and reduction in thickness of retinal layers were reversed in ZZRext-treated diabetic rats. Retinal gene expression of tumor necrosis factor-α, interleukin (IL)-1β, IL-6, vascular endothelial growth factor, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 were all decreased in ZZRext-treated diabetic rats. Moreover, ZZRext treatment not only inhibited the nuclear factor κB (NF-κB) activation, but also downregulated the protein expression of p38 mitogen-activated protein kinase (MAPK) in diabetic retina. In conclusion, the results suggest that the retinal protective effects of ZZRext occur through improved retinal structural change and inhibiting retinal inflammation. The antiretinopathy property of ZZRext might be related to the downregulation of p38 MAPK and NF-κB signal transduction induced by diabetes.

The ethanol extract of Zingiber zerumbet rhizomes mitigates vascular lesions in the diabetic retina

Diabetic retinopathy (DR) is a common diabetic eye disease which is well-known as the result of microvascular retinal changes. Although the ethanol extract from Zingiber zerumbet (L.) Smith rhizome (EEZZR) has been indicated to ameliorate hyperglycemia in diabetes, its protective effect on DR remains unclear. The aim of this study was to determine the effects of EEZZR on DR in streptozotocin (STZ) diabetic rats. Diabetic rats were treated orally with EEZZR (200, 300 mg/kg per day) or calcium dobesilate (CD; 500 mg/kg per day) for 12 weeks. EEZZR displayed similar characteristics to CD in reducing blood-retinal barrier permeability in diabetic rats. Retinal histopathological observation showed that retinal vessels were decreased in EEZZR-treated diabetic rats. EEZZR decreased the increased retinal expression of vascular endothelial growth factor (VEGF) and upregulate the expressions of renal pigment epithelium-derived factor (PEDF) in diabetic rats. Retinal mRNA expression of tumor necrosis factor-α, interleukin (IL)-1, IL-6, monocyte chemotactic proteins-1, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 were all decreased in EEZZR-treated diabetic rats. Moreover, EEZZR could attenuate phosphorylation of nuclear factor Kappa B (NF-κB) p65 and extracellular signal-regulated kinase (ERK)1/2 as well as inhibit the nuclear translocation of pNF-κB p65 induced by diabetes. In conclusion, restoring the balance between stimulators and inhibitors of angiogenesis may be associated with the protective effect of EEZZR on DR. In addition, EEZZR can ameliorate retinal inflammation via transrepression of NF-κB and inhibition of ERK1/2 signaling pathway.

Non-traditional systemic treatments for diabetic retinopathy: an evidence-based review

The rapid escalation in the global prevalence diabetes, with more than 30% being afflicted with diabetic retinopathy (DR), means it is likely that associated vision-threatening conditions will also rise substantially. This means that new therapeutic approaches need to be found that go beyond the current standards of diabetic care, and which are effective in the early stages of the disease. In recent decades several new pharmacological agents have been investigated for their effectiveness in preventing the appearance and progression of DR or in reversing DR; some with limited success while others appear promising. This up-to-date critical review of non-traditional systemic treatments for DR is based on the published evidence in MEDLINE spanning 1980-December 2014. It discusses a number of therapeutic options, paying particular attention to the mechanisms of action and the clinical evidence for the use of renin-angiotensin system blockade, fenofibrate and calcium dobesilate monohydrate in DR.

Effect of calcium dobesilate on occurrence of diabetic macular oedema (CALDIRET study): randomised, double-blind, placebo-controlled, multicentre trial

BACKGROUND

Medical treatment for diabetic retinopathy could have an important role in prevention of complications such as visual loss. We aimed to assess the effect of calcium dobesilate on occurrence of diabetic macular oedema.

METHODS

We undertook a randomised, double-blind, placebo-controlled, multicentre study in 40 centres in 11 countries. We enrolled outpatients with adult-onset type 2 diabetes and mild-to-moderate non-proliferative diabetic retinopathy, and randomly allocated them via sealed envelopes either calcium dobesilate (1500 mg per day) or placebo. The primary endpoint was development of clinically significant macular oedema (CSME) within a follow-up period of 5 years. Patients who dropped out of the study early were censored. Analysis was by intention to treat.

FINDINGS

We enrolled 635 patients. 324 were randomly allocated calcium dobesilate and 311 were assigned placebo. In the calcium dobesilate group, 86 patients developed CSME compared with 69 in the placebo group. Accounting for censored cases, estimated cumulative 5-year CSME probability was 35% and 28%, respectively (hazard ratio 1.32, 95% CI 0.96-1.81; p=0.0844). Adverse events did not differ between treatment groups (78 [24%] on calcium dobesilate and 90 [29%] with placebo). No relevant drug-related complications were noted. Nine patients (3%) died in the calcium dobesilate group and eight (3%) deaths were recorded on placebo.

INTERPRETATION

Calcium dobesilate did not reduce the risk of development of CSME.