Ameliorative effects of thymoquinone against eye lens changes in streptozotocin diabetic rats

Low-dose rosmarinic acid and thymoquinone accelerate wound healing in retinal pigment epithelial cells

PURPOSE

Thymoquinone (TQ) and rosmarinic acid (RA) are two biologically active compounds found in plants and that possess remarkable anti-oxidant and anti-inflammatory properties. The present study aimed to investigate the potential protective effects of RA and TQ, which have known anti-inflammatory and anti-oxidant effects, on retinal damage by establishing a wound healing model for retinal pigment epithelial cells (ARPE-19).

METHOD

To this end, IC50 doses of RA and TQ in ARPE-19 cells were calculated by MTT assay. Both agents were administered at IC50, IC50/2 and IC50/4 doses for wound healing assay, and wound closure percentages were analyzed. Since the best wound healing was found at IC50/4 dose (low dose) for both agents, other biochemical and molecular analyses were planned to be performed using these doses. Following low dose RA and TQ treatments, the cells were lysed and TGF-β1 and MMP-9 levels were analyzed by ELISA technique from the cell lysates obtained. In addition, the mRNA expression levels of TLR3, IFN-γ and VEGF were calculated by RT-PCR technique.

RESULTS

Low dose of RA and TQ dramatically increased wound healing. RA may have achieved this by increasing levels of MMP-9 and TLR-3. In contrast, the mRNA expression level of VEGF remained unchanged. TQ accelerated wound healing by increasing both the protein levels of TGF-β1 and MMP-9. Furthermore, low dose of TQ decreased both TLR3 and IFN-γ mRNA expression levels.

CONCLUSION

Low doses of RA and TQ were clearly demonstrated to have protective properties against possible damage to retinal pigment epithelial cells.

Thymoquinone in Ocular Neurodegeneration: Modulation of Pathological Mechanisms via Multiple Pathways

Thymoquinone is a naturally occurring compound and is the major component of Nigella sativa, also known as black seed or black cumin. For centuries thymoquinone has been used especially in the Middle East traditionally to treat wounds, asthma, allergies, fever, headache, cough, hypertension, and diabetes. Studies have suggested beneficial effects of thymoquinone to be attributed to its antioxidant, antibacterial, anti-oxidative stress, anti-inflammatory, and neuroprotective properties. Recently, there has been a surge of interest in thymoquinone as a treatment for neurodegeneration in the brain, such as that seen in Alzheimer’s (AD) and Parkinson’s diseases (PD). In vitro and in vivo studies on animal models of AD and PD suggest the main neuroprotective mechanisms are based on the anti-inflammatory and anti-oxidative properties of thymoquinone. Neurodegenerative conditions of the eye, such as Age-related Macular Degeneration (AMD) and glaucoma share at least in part similar mechanisms of neuronal cell death with those occurring in AD and PD. This review aims to summarize and critically analyze the evidence to date of the effects and potential neuroprotective actions of thymoquinone in the eye and ocular neurodegenerations.

The effects of caffeic acid phenethyl ester on retina in a diabetic rat model

PURPOSE

We aimed to investigate the effect of caffeic acid phenethyl ester (CAPE) on retinal apoptosis and oxidative stress parameters in streptozotocin (STZ) induced diabetic rat model.

METHODS

This study included 3 groups; control, STZ, and STZ + CAPE. The rats in STZ, and STZ + CAPE groups were injected with STZ (35 mg/kg, i.p.) for induction of diabetes. In the STZ + CAPE group, 10 µmol/kg of CAPE were intraperitoneally injected for 4 weeks. Control and STZ groups were given only intraperitoneal vehicle (saline). Rats were anaesthetized and sacrificed on the 4th week of the experiment. Total anti-oxidant status (TAS), and total oxidant status (TOS) were measured on the dissected retinal tissues. Oxidative stress index (OSI) was also calculated. Fellow eyes were used for histopathologic evaluation with caspase-3 and matrix metalloproteinase-2 (MMP-2) and MMP-9 evaluation.

RESULTS

TAS levels were similar between groups (p = 0.71). However, CAPE treatment prevented the elevation of the TOS in the STZ + CAPE group compared to the STZ group (30.93 ± 9.97 vs 61.53 ± 24.7 nmol H₂O₂ Eq/mg protein, p = 0.007). OSI was also significantly lower in the STZ + CAPE group than that of the STZ group (20.01 ± 5.87 vs. 37.90 ± 14.32, respectively, p = 0.007). Retinal caspase-3 staining, MMP-2 and MMP-9 scores were not different between groups (p > 0.05 for all).

CONCLUSION

The present study demonstrated that CAPE treatment may decrease the oxidative stress in the retina in STZ induced diabetic rat model. However, apoptosis was not observed in the retina. The retinal apoptosis cannot be shown probably due to a shorter period of diabetes.

Citrus hystrix leaf extract attenuated diabetic-cataract in STZ-rats

Diabetic cataract causes severe vision loss. This study evaluated the effects of hesperidin-standardized Citrus hystrix leaf flavonoids-rich extract (CLE) on diabetic-cataract development. Streptozotocin-induced diabetic rats were orally given 150 and 300 mg CLE/kg body-weight. These were compared with non-treated diabetic or healthy rats as controls, over 8 weeks. The CLE gradually attenuated fasting blood glucose (FBG), biomarkers for inflammation (Tumor necrosis factor alpha TNF-α; prostaglandin E2 PGE2); vascular permeability, (Vascular endothelial growth factor VEGF); and oxidative stress, (malondialdehyde MDA). The diabetic cataract was significantly mitigated by the 150 mg CLE/kg dose. Good correlations were found between cataract incidence with FBG (r²  = 0.90), serum PGE2 (r²  = 0.91), MDA (r²  = 0.99), VEGF (r²  = 0.71), but not with TNF-α levels (r²  = 0.49) suggesting the serum FBG, PGE2, MDA, and possibly the VEGF levels may help to predict the cataract risks. The CLE mitigated cataract probably by attenuating hyperglycaemia, inflammation, lens fluid influx, vascular leakage, lens osmotic-imbalance, and fibers over-hydration. PRACTICAL APPLICATIONS: The study shows the flavonoids-rich Citrus hystrix leaf consumption, effectively attenuated diabetes (fasting blood glucose) and mitigated diabetic cataract. It help reduce diabetes-related hyperglycaemia, oxidative stress, inflammation, and vascular leakage. The evidences were the CLE consumptions reduced the serum biomarkers tumor necrosis factor-alpha TNF-α; prostaglandin E2 PGE2, vascular endothelial growth factor (VEGF), and malondialdehyde (MDA). The C. hystrix leaf contains hesperidin, apiin, diosmin, saponarin, apigetrin, rutin and xanthotoxol, and other flavonoid glucosides. The study also showed good correlations between cataract incidence with fasting blood glucose FBG (r²  = 0.90), serum PGE2 (r²  = 0.91), and MDA (r²  = 0.99), and less closely with VEGF (r²  = 0.71) suggesting these serum biomarkers may help predict cataract risks. The CLE indicated cataract mitigation properties probably by attenuating FBG, inflammation, lens fluid influx, lens osmotic-imbalance, and fibers over-hydration.

Thymoquinone protects human retinal pigment epithelial cells against hydrogen peroxide induced oxidative stress and apoptosis

Oxidative stress in retinal pigment epithelium (RPE) cells may contribute to the progression of age-related macular degeneration. Thymoquinone (TQ), an active component derived from Nigella sativa, possesses antioxidative effect. However, the role of TQ in RPE cells under oxidative stress condition remains unclear. The present study aimed to examine the protective effect of TQ against hydrogen peroxide (H₂ O₂ )-induced oxidative stress in human RPE cells. Our results showed that TQ improved the cell viability and apoptosis in H₂ O₂ -induced ARPE cells. We also found that the levels of reactive oxygen species and malondialdehyde induced by H₂ O₂ were reduced after the pretreatment of TQ. In addition, the inhibitory effect of H₂ O₂ on the glutathione (GSH) level and superoxide dismutase activity was markedly attenuated by TQ pretreatment. Moreover, TQ enhanced the activation of Nrf2/heme oxygenase 1 (HO-1) signaling pathway in H₂ O₂ -induced ARPE cells. Knockdown of Nrf2 abolished the protective effect of TQ on H₂ O₂ -induced oxidative damage. These results suggested that TQ protected ARPE cells from H₂ O₂ -induced oxidative stress and apoptosis via the Nrf2/HO-1 signaling pathway.

Spice-Derived Bioactive Ingredients: Potential Agents or Food Adjuvant in the Management of Diabetes Mellitus

Spices possess tremendous therapeutic potential including hypoglycemic action, attributed to their bioactive ingredients. However, there is no study that critically reviewed the hypoglycemic potency, safety and the bioavailability of the spice-derived bioactive ingredients (SDBI). Therefore, the aim of the study was to comprehensively review all published studies regarding the hypoglycemic action of SDBI with the purpose to assess whether the ingredients are potential hypoglycemic agents or adjuvant. Factors considered were concentration/dosages used, the extent of blood glucose reduction, the IC50 values, and the safety concern of the SDBI. From the results, cinnamaldehyde, curcumin, diosgenin, thymoquinone (TQ), and trigonelline were showed the most promising effects and hold future potential as hypoglycemic agents. Conclusively, future studies should focus on improving the tissue and cellular bioavailability of the promising SDBI to achieve greater potency. Additionally, clinical trials and toxicity studies are with these SDBI are warranted.

Baicalin and chrysin mixture imparts cyto-protection against methylglyoxal induced cytotoxicity and diabetic tubular injury by modulating RAGE, oxidative stress and inflammation

Protective effect of mixture of flavonoids baicalin and chrysin (BCH) was studied against methylglyoxal (MG, a precursor of AGEs) induced cytotoxicity in NRK 52E kidney epithelial cells. Flow cytometry and microscopic analysis showed increased ROS generation, compromised antioxidant status, depolarization of mitochondria and apoptosis in MG stressed cells which were significantly transformed (p≤0.01) during BCH co-treatment. In vivo studies in streptozotocin induced diabetic rats increased protein levels of iNOS, protein kinase C (PKC) and decreased IκB which was modulated by oral BCH treatment (75mg baicalin and 10mg chrysin/kg b.wt.). Increased levels of AGEs and their receptor proteins (RAGE) in diabetic rats were reduced significantly (p≤0.01) in BCH treated group. Renal tubular injuries and deranged kidney function were significantly improved in BCH treated animals. The results indicate that the protection accorded by BCH through its antioxidant and anti-inflammatory effects can be explored for management of diabetic nephropathy.

Thymoquinone ameliorated elevated inflammatory cytokines in testicular tissue and sex hormones imbalance induced by oral chronic toxicity with sodium nitrite

Scientific evidence illustrated the health hazards of exposure to nitrites for prolonged time. Nitrites affected several body organs due to oxidative, inflammatory and apoptosis properties. Furthermore, thymoquinone (TQ) had curative effects against many diseases. We tried to discover the impact of both sodium nitrite and TQ on inflammatory cytokines contents in testicular tissues and hormonal balance both in vivo and in vitro. Fifty adult male SD rats received 80mg/kg sodium nitrite and treated with either 25 or 50mg/kg TQ daily by oral-gavage for twelve weeks. Testis were removed for sperms' count. Testicular tissue homogenates were used for assessment of protein and gene expression of IL-1β, IL-6, TNF-α, Nrf2 and caspase-3. Serum samples were used for measurement of testosterone, LH, FSH and prolactin. Moreover, all the parameters were measured in human normal testis cell-lines, CRL-7002. Sodium nitrite produced significant decrease in serum testosterone associated with raised FSH, LH and prolactin. Moreover, sodium nitrite significantly elevated TNF-α, IL-1β, IL-6, caspase-3 and reduced Nrf2. TQ significantly reversed all these effects both in vivo and in vitro. In conclusion, TQ ameliorated testicular tissue inflammation and restored the normal balance of sex hormones induced by sodium nitrite both in vivo and in vitro.