Oxidative stress in the optic nerve and cortical visual area of steptozotocin-induced diabetic Wistar rats: Blockade with a selective bradykinin B1 receptor antagonist

The retina-brain axis and diabetic retinopathy

Diabetic retinopathy (DR) is a major contributor to permanent vision loss and blindness. Changes in retinal neurons, glia, and microvasculature have been the focus of intensive study in the quest to better understand DR. However, the impact of diabetes on the rest of the visual system has received less attention. There are reports of associations of changes in the visual system with preclinical and clinical manifestations of diabetes. Simultaneous investigation of the retina and the brain may shed light on the mechanisms underlying neurodegeneration in diabetics. Additionally, investigating the links between DR and other neurodegenerative disorders of the brain including Alzheimer's and Parkinson's disease may reveal shared mechanisms for neurodegeneration and potential therapy options.

Protection against experimental cisplatin-induced optic nerve toxicity using resveratrol: A rat model study

AIM

To investigate the effects of resveratrol on oxidative stress and inflammation parameters and histological alterations in cisplatin-induced optic nerve damage in a mouse model.

MATERIAL AND METHOD

Thirty-six albino Wistar male rats were divided into three groups as control, 5 mg/kg cisplatin-administered (Cis) and 5 mg/kg cisplatin + 25 mg/kg resveratrol-administered (Cis + Res) animals. At the end of the experimental period, the rats were sacrificed with high-dose (50 mg/kg) thiopental sodium, and their optic nerves were dissected. Malondialdehyde (MDA), total glutathione (tGSH), total oxidant status (TOS), total antioxidant status (TAS), tumour necrosis factor alpha (TNF-α), nuclear factor kappa B (NF-KB) levels, and histopathological findings were assessed using the optic nerve tissues.

RESULTS

In the Cis + Res group, the MDA, TOS, OSI, TNF-a and NFK-B levels were significantly lower and the tGSH and TAS levels were significantly higher compared with the Cis group (P = 0.001). In histological evaluations, there were dilated and congested blood vessels, destruction, oedema, degeneration, haemorrhage, and proliferating capillaries indicating the presence of inflammation and damage only in the Cis-administered group. However, in the Cis + Res group, the histological findings were very similar to the healthy controls.

CONCLUSION

Resveratrol is a promising neuroprotective agent for cisplatin-induced optic nerve toxicity with its anti-oxidant and anti-inflammatory effects. Further investigations are needed to evaluate the possible therapeutic effects on other optic nerve toxicities.

How curcumin affects hyperglycemia-induced optic nerve damage: A short review

Considered to be one of the most important non-contagious systemic diseases worldwide, diabetes mellitus is still a topical issue on the health agenda with the problems it causes. Exposure to long-term hyperglycemia causes diabetic complications (diabetic neuropathy, nephropathy and retinopathy). The optic nerve can suffer damage by both diabetic retinopathy and neuropathy during diabetes, both because it is formed by axons of retinal ganglion cells and these axons belong to the central nervous system. The issue of hyperglycemia on the optic nerve have been described as diabetic papillopathy, posterior ischemic optic neuropathy, nonarteritic anterior ischemic optic neuropathy and optic atrophy in clinical studies. Experimental studies indicated axon-myelin degeneration in addition to microvascular and ultrastructural changes caused by the hyperglycemia-induced optic nerve damage. Although there are several proposed biochemical mechanisms to cause these damages, oxidative stress emerges as an important factor among them. Oxidative stress leads to pathological state on the nerve cells by affecting the DNA, protein and lipids at different levels. These are causing deterioration on nerve conduction velocity, myelin sheath and nerve structure, neurotrophic support system, glial cells and nerve function. Curcumin, as an important antioxidant, can be an ideal prophylactic agent to eliminate damages on optic nerve. Curcumin helps to regulate the balance of antioxidant and reactive oxygen species by targeting various molecules (NF-κB, STAT3, MAPK, Mfn2, Nrf2, pro-inflammatory cytokines). In addition, it shows healing or preventive effects on myelin sheath damage via regulating ferritin protein in oligodendrocytes. It is also effective in preventing neurovascular damage.

Bradykinin Type 1 Receptor - Inducible Nitric Oxide Synthase: A New Axis Implicated in Diabetic Retinopathy

Compelling evidence suggests a role for the inducible nitric oxide synthase, iNOS, and the bradykinin type 1 receptor (B1R) in diabetic retinopathy, including a possible control of the expression and activity of iNOS by B1R. In diabetic retina, both iNOS and B1R contribute to inflammation, oxidative stress, and vascular dysfunction. The present study investigated whether inhibition of iNOS has any impact on inflammatory/oxidative stress markers and on the B1R-iNOS expression, distribution, and action in a model of type I diabetes. Diabetes was induced in 6-week-old Wistar rats by streptozotocin (65 mg.kg^-1, i.p.). The selective iNOS inhibitor 1400W (150 μg.10 μl^-1) was administered twice a day by eye-drops during the second week of diabetes. The retinae were collected 2 weeks after diabetes induction to assess the protein and gene expression of markers by Western blot and qRT-PCR, the distribution of iNOS and B1R by fluorescence immunocytochemistry, and the vascular permeability by the Evans Blue dye technique. Diabetic retinae showed enhanced expression of iNOS, B1R, carboxypeptidase M (involved in the biosynthesis of B1R agonists), IL-1β, TNF-α, vascular endothelium growth factor A (VEGF-A) and its receptor, VEGF-R2, nitrosylated proteins and increased vascular permeability. All those changes were reversed by treatment with 1400W. Moreover, the additional increase in vascular permeability in diabetic retina induced by intravitreal injection of R-838, a B1R agonist, was also prevented by 1400W. Immunofluorescence staining highlighted strong colocalization of iNOS and B1R in several layers of the diabetic retina, which was prevented by 1400W. This study suggests a critical role for iNOS and B1R in the early stage of diabetic retinopathy. B1R and iNOS appear to partake in a mutual auto-induction and amplification loop to enhance nitrogen species formation and inflammation in diabetic retina. Hence, B1R-iNOS axis deserves closer scrutiny in targeting diabetic retinopathy.

Antitumor activity of cell-penetrant kinin B1 receptor antagonists in human triple-negative breast cancer cells

High nuclear expression of G protein-coupled receptors, including kinin B1 receptors (B1R), has been observed in several human cancers, but the clinical significance of this is unknown. We put forward the hypothesis that these "nuclearized" kinin B1R contribute to tumorigenicity and can be a new target in anticancer strategies. Our initial immunostaining and ultrastructural electron microscopy analyses demonstrated high B1R expression predominantly located at internal/nuclear compartments in the MDA-MB-231 triple-negative breast cancer (TNBC) cell line as well as in clinical samples of patients with TNBC. On the basis of these findings, in the present study, we evaluated the anticancer therapeutic potential of newly identified, cell-permeable B1R antagonists in MDA-MB-231 cells (ligand-receptor binding/activity assays and LC-MS/MS analyses). We found that these compounds (SSR240612, NG67, and N2000) were more toxic to MDA-MB-231 cells in comparison with low- or non-B1R expressing MCF-10A normal human mammary epithelial cells and COS-1 cells, respectively (clonogenic, MTT proliferative/cytocidal assays, and fluorescence-activated cell-sorting (FACS)-based apoptosis analyses). By comparison, the peptide B1R antagonist R954 unable to cross cell membrane failed to produce anticancer effects. Furthermore, the putative mechanisms underlying the anticancer activities of cell-penetrant B1R antagonists were assessed by analyzing cell cycle regulation and signaling molecules related to cell survival and apoptosis (FACS and western blot). Finally, drug combination experiments showed that cell-penetrant B1R antagonists can cooperate with suboptimal doses of chemotherapeutic agents (doxorubicin and paclitaxel) to promote TNBC death. This study provides evidence on the potential value of internally acting kinin B1R antagonists in averting growth of breast cancer.