Neuromodulation Therapies in Pre-Clinical Models of Traumatic Brain Injury: Systematic Review and Translational Applications

Traumatic brain injury (TBI) has been associated with several lasting impairments that affect quality of life. Pre-clinical models of TBI have been studied to further our understanding of the underlying short-term and long-term symptomatology. Neuromodulation techniques have become of great interest in recent years as potential rehabilitative therapies after injury because of their capacity to alter neuronal activity and neural circuits in targeted brain regions. This systematic review aims to provide an overlook of the behavioral and neurochemical effects of transcranial direct current stimulation (tDCS), transcranial magnetic stimulation (TMS), deep brain stimulation (DBS), and vagus nerve stimulation (VNS) in pre-clinical TBI models. After screening 629 abstracts, 30 articles were pooled for review. These studies showed that tDCS, TMS, DBS, or VNS delivered to rodents restored TBI-induced deficits in coordination, balance, locomotor activity and improved cognitive impairments in memory, learning, and impulsivity. Potential mechanisms for these effects included neuroprotection, a decrease in apoptosis, neuroplasticity, and the restoration of neural circuit abnormalities. The translational value, potential applicability, and the interpretation of these findings in light of outcome data from clinical trials in patients with TBI are discussed.

Sex differences in long-term fear and anxiety-like responses in a preclinical model of PTSD

With a high prevalence of posttraumatic stress disorder (PTSD) in females, studying sex differences in preclinical models is of substantial importance. We have previously employed behavioural criteria to identify and characterize a subpopulation of rats that presented impaired fear extinction and long-term fear and anxiety responses following fear conditioning. We now exposed male and female rats to fear conditioning and extinction and segregated the animals into weak- (WE) and strong-extinction (SE) groups based on behavioural scores during extinction. Animals were subsequently tested for tone and context recall, as well as anxiety-like responses in the marble burying and novelty suppression of feeding (NSF) tests. Vaginal lavages were collected to characterize the phase of the estrous cycle during fear extinction. We found that females had reduced freezing during tone recall and a lower latency to feed in the NSF test. No differences were found in females undergoing extinction during high and low estrogen phases of the cycle in any of the performed tests. Overall, the percentage of animals that presented WE and SE phenotypes was similar in males and females. Both, WE males and females had increased freezing during tone and context recall. Along with our previous reports, WE males presented anxiety-like responses, particularly in the NSF compared to SE animals. In contrast, WE females buried less marbles than their SE mates. Future investigation including a larger number of behavioural tests are certainly required to corroborate our findings and ascertain potential mechanisms to explain the differences observed in our study.

Hesperetin-Based Hydrogels Protect the Skin against UV Radiation-Induced Damage

UV radiation can cause damages, such as erythema, skin photoaging, and carcinogenesis. The adoption of protective measures against sun exposure is essential to prevent these damages, and the interest in using natural substances as an alternative for photoprotection is growing. Thus, hesperetin with antioxidant, anti-inflammatory, and anticancer properties is a promising substance to be used with photochemopreventive action and to protect the skin from damage induced by UV radiation. Therefore, the present study aimed to develop a topical formulation based on AAMVPC gel containing hesperetin and evaluate its photoprotective effect on the skin of rats exposed to UVA-UVB radiation. The animals were submitted to the irradiation protocol UVA-UVB, and at the end, erythema, lipid peroxidation, and activity of the antioxidant enzyme catalase and superoxide dismutase were evaluated. Additionally, it evaluated the activity of myeloperoxidase and histological changes. The formulation presented a rheological and spreadability profile suitable for cutaneous application. In vivo results demonstrated that the topical formulation of AAMVPC gel containing hesperetin at a concentration of 10% protected the skin from damage induced by UVA-UVB radiation, with the absence of erythema, lipid lipoperoxidation, and inflammation (low myeloperoxidase activity), and increased catalase and superoxide dismutase activities. The morphology and architecture of the dermo-epidermal tissue of these animals were like those observed under normal conditions (non-irradiated animals). Thus, the results showed that hesperetin was able to protect the animals' skin against UV radiation-induced skin damage and the protection mechanisms may be related to the antioxidant and anti-inflammatory properties of this natural product.

Nephrotoxic Effects Caused by Occupational Exposure to Agrochemicals in a Region of Northeastern Brazil: A Cross-Sectional Study

The objective of the present study was to evaluate the renal function of rural workers in a city of northeastern Brazil. A cross-sectional study was carried out with 208 workers in Boquim, Sergipe, Brazil. Renal function markers and butyrylcholinesterase (BChE) were evaluated and the glomerular filtration rate (GFR) was determined. The sample consisted mainly of illiterate males with a low usage of personal protective equipment and no training. Approximately 40% had some level of renal failure. Relative risk (1.59) of GFR alteration was higher in workers with more than 5 yr of exposure, mainly to organophosphates. Workers more than 60 yr of age presented a 17.06 greater risk for manifesting acute intoxication. Butyrylcholinesterase reduction was associated with reports of intoxication (relative risk of 11.36). We concluded that exposure to pesticides represented a risk factor for the development of nephrotoxic effects and alteration of renal function, which reinforced the need to implement measures to protect rural workers. Environ Toxicol Chem 2021;40:1132-1138. © 2020 SETAC.

NOX-dependent reactive oxygen species production underlies arrhythmias susceptibility in dexamethasone-treated rats

Dexamethasone is the most clinically used glucocorticoid with an established role in the treatment of a wide spectrum of inflammatory-related diseases. While the therapeutic actions are well known, dexamethasone treatment causes a number of cardiovascular side effects, which are complex, frequent and, in some cases, clinically unnoticeable. Here, we investigated whether a therapeutic regimen of dexamethasone affects cardiac arrhythmogenesis, focusing on the contribution of Nox-derived reactive oxygen species (ROS). Male Wistar rats were treated with dexamethasone (2 mg/kg, i.p.) for 7 days. Afterward, hemodynamic measurements, autonomic modulation, left ventricular function, cardiac fibrosis, reactive oxygen species (ROS) generation, Nox protein expression, superoxide dismutase (SOD) and catalase activities, and arrhythmias incidence were evaluated. Here, we show that dexamethasone increases blood pressure, associated with enhanced cardiac and vascular sympathetic modulation. Moreover, a marked increase in the cardiac ROS generation was observed, whereas the enhanced SOD activity did not prevent the higher levels of lipid peroxidation in the dexamethasone group. On the other hand, increased cardiac Nox 4 expression and hydrogen peroxide decomposition rate was observed in dexamethasone-treated rats, while Nox 2 remained unchanged. Interestingly, although preserved ventricular contractility and β-adrenergic responsiveness, we found that dexamethasone-treated rats displayed greater interstitial and perivascular fibrosis than control. Surprisingly, despite the absence of arrhythmias at basal condition, we demonstrated, by in vivo and ex vivo approaches, that dexamethasone-treated rats are more susceptible to develop harmful forms of ventricular arrhythmias when challenged with pharmacological drugs or burst pacing-induced arrhythmias. Notably, concomitant treatment with apocynin, an inhibitor of NADPH oxidase, prevented these ectopic ventricular events. Together, our results reveal that hearts become arrhythmogenic during dexamethasone treatment, uncovering the pivotal role of ROS-generating NADPH oxidases for arrhythmias vulnerability.

d-Limonene Ameliorates Myocardial Infarction Injury by Reducing Reactive Oxygen Species and Cell Apoptosis in a Murine Model

Myocardial infarction (MI) leads to high mortality, and pharmacological or percutaneous primary interventions do not significantly inhibit ischemia/reperfusion injuries, particularly those caused by oxidative stress. Recently, research groups have evaluated several naturally occurring antioxidant compounds for possible use as therapeutic alternatives to traditional treatments. Studies have demonstrated that d-limonene (DL), a monoterpene of citrus fruits, possesses antioxidant and cardiovascular properties. Thus, this work sought to elucidate the mechanisms of protection of DL in an isoproterenol-induced murine MI model. It was observed that DL (10 μmol) attenuated 40% of the ST elevation, reduced the infarct area, prevented histological alterations, abolished completely oxidative stress damage, restored superoxide dismutase activity, and suppressed pro-apoptotic enzymes. In conclusion, the present study demonstrated that DL produces cardioprotective effects from isoproterenol-induced myocardial infarction in Swiss mice through suppression of apoptosis.

Carvacrol suppresses LPS-induced pro-inflammatory activation in RAW 264.7 macrophages through ERK1/2 and NF-kB pathway

Macrophages are immune system cells that respond to various pathogenic insults. The recognition of antigens is performed through receptors such as TLR4 and RAGE, which recognize pathogen-associated patterns (PAMPs), including lipopolysaccharide (LPS) from Gram-negative bacteria. Carvacrol (CAR) is a phenolic compound found in some essential oils commonly used in folk medicine for treatment of inflammation-related diseases. Previous works observed strong antioxidant actions and some anti-inflammatory effects by CAR in in vivo and in vitro assays. However, the potential pharmacological application of CAR remains limited as details on its mechanisms of action are still missing. Here we investigated the molecular pathways by which CAR acts on LPS-mediated pro-inflammatory activation of RAW 264.7 macrophages. CAR 100 μM protected cells against loss of cell viability induced by LPS (1 μg/mL). Pre-incubation with CAR prevented LPS-induced ERK1/2 phosphorylation, but it had no effect on p38 and JNK activation. The effect of LPS on NF-kB (p65) translocation from cytoplasm to nucleus was inhibited by CAR, as well as NF-kB transcriptional activation. Moreover, LPS-elicited release of TNF-α and IL-1β were inhibited by CAR, as well as activation of phagocytic activity. Such effects may be related to the antioxidant effect of CAR, as the LPS-induced increase in reactive species (RS) production (assessed by DCFH oxidation) and nitric oxide (NO) production (assessed by nitrite quantification) were inhibited by CAR. Altogether, these results demonstrate that CAR exerts relevant anti-inflammatory actions through a cellular mechanism involving ERK1/2 and NF-kB inhibition and possibly related to the antioxidant properties of this phenolic compound.

Guarana supplementation attenuated obesity, insulin resistance, and adipokines dysregulation induced by a standardized human Western diet via brown adipose tissue activation

Obesity is a metabolic disorder associated with adverse health consequences that has increased worldwide at an epidemic rate. This has encouraged many people to utilize nonprescription herbal supplements for weight loss without knowledge of their safety or efficacy. However, mounting evidence has shown that some herbal supplements used for weight loss are associated with adverse effects. Guarana seed powder is a popular nonprescription dietary herb supplement marketed for weight loss, but no study has demonstrated its efficacy or safety when administered alone. Wistar rats were fed four different diets (low-fat diet and Western diet with or without guarana supplementation) for 18 weeks. Metabolic parameters, gut microbiota changes, and toxicity were then characterized. Guarana seed powder supplementation prevented weight gain, insulin resistance, and adipokine dysregulation induced by Western diet compared with the control diet. Guarana induced brown adipose tissue expansion, mitochondrial biogenesis, uncoupling protein-1 overexpression, AMPK activation, and minor changes in gut microbiota. Molecular docking suggested a direct activation of AMPK by four guarana compounds tested here. We propose that brown adipose tissue activation is one of the action mechanisms involved in guarana supplementation-induced weight loss and that direct AMPK activation may underlie this mechanism. In summary, guarana is an attractive potential therapeutic agent to treat obesity.

Obese rats are more vulnerable to inflammation, genotoxicity and oxidative stress induced by coal dust inhalation than non-obese rats

Obesity is an important nutritional disorder worldwide. Its association with environmental pollution may trigger an increase in oxidative stress and inflammatory parameters. Coal is a resource used throughout the world as an important fuel source for generating electricity. The ashes released by the coal combustion cause serious problems for human health due to their high toxicity and their capacity to bioaccumulate. The aim of this work was to investigate the effects of coal dust inhalation in the organs of obese and non-obese Wistar rats. Pro-inflammatory cytokines, oxidative stress, oxidative damage, histological analysis, comet assay, and micronuclei were investigated. Both obesity and coal dust inhalation increased the pro-inflammatory cytokines IL-1β and TNF-α and decreased HSP70 levels in serum, however, in obese animals that inhaled coal dust these changes were more pronounced. Liver histological analysis showed severe microvesicular steatosis in obese animals that inhaled coal dust. Lung histologic investigation showed abnormalities in lung structure of animals exposed to coal dust and showed severe lung distensibility in obese animals exposed to coal dust. The comet assay showed DNA damage in animals subjected to coal. In addition, there were modulations in enzymatic activities and damage to protein and lipids. Based on our results, the coal dust inhalation can potentiate the pro-inflammatory profile present in obese rats. We also observed an increase in the protein oxidative damage in obese rats that inhaled coal dust. Taken together, our results suggest that the combination of obesity and coal inhalation increased the risks of the development of diseases related to oxidative stress and inflammation.

Effects of Carvacrol, Thymol and essential oils containing such monoterpenes on wound healing: a systematic review

Objectives

The treatment of wounds accounts for a considerable fraction of health expenses as well as serious socioeconomic problems. The use of natural substances stands out as a source of new therapeutic discoveries for the wound healing. Thus, this review compiled scientific findings on the applicability of carvacrol and thymol, or essential oils containing at least one of these compounds, for the treatment of wounds.

Methods

This review was performed at PubMed, SCOPUS, Web of Science databases using keywords as wound healing, thymol/carvacrol and essential oils. Thirteen studies were selected for discussion.

Key findings

Thymol/carvacrol was able to act in the three phases of wound healing. In the first phase, they showed modulatory effect of the inflammatory cytokines, oxidative stress and antimicrobial power. In the second phase, they promoted re-epithelialization, angiogenesis and development of granulation tissue. Finally, in the third phase, they improve the collagen deposition and modulated the growth of fibroblasts and keratinocytes.

Conclusions

These compounds present a high potential for the development of new therapeutic for wound repair. However, dose, efficacy and safety of these compounds for the treatment of wounds, as well as the mechanisms by which those effects can be observed, are challenges for future studies.

Resistance exercise mediates remote ischemic preconditioning by limiting cardiac eNOS uncoupling

BACKGROUND

Currently viewed as a complementary non-pharmacological intervention for preventing cardiac disorders, long-term aerobic training produces cardioprotection through remote ischemic preconditioning (RIPC) mechanisms. However, RIPC triggered by acute exercise remains poorly understood. Although resistance exercise (RE) has been highly recommended by several public health guidelines, there is no evidence showing that RE mediates RIPC. Hence, we investigated whether RE induces cardiac RIPC through nitric oxide synthase (NOS)-dependent mechanism.

METHODS AND RESULTS

Acute RE at 40% of the maximal load augmented systemic nitrite levels, associated with increased cardiac eNOS phosphorylation, without affecting nNOS activity. Using an experimental model of myocardial infarction (MI) through ischemia-reperfusion (IR), RE fully prevented the loss of cardiac contractility and the extent of MI size compared to non-exercised (NE) rats. Moreover, RE mitigated aberrant ST-segment and reduced life-threatening arrhythmias induced by IR. Importantly, inhibition of NOS abolished the RE-mediated cardioprotection. After IR, NE rats showed increased cardiac eNOS activity, associated with reduced dimer/monomer ratio. Supporting the pivotal role of eNOS coupling during MI, non-exercised rats displayed a marked generation of reactive oxygen species (ROS) and oxidative-induced carbonylation of proteins, whereas RE prevented these responses. We validated our data demonstrating a restoration of physiological ROS levels in NE + IR cardiac sections treated with BH₄, a cofactor oxidatively depleted during eNOS uncoupling, while cardiac ROS generation from exercised rats remained unchanged, suggesting no physiological needs of supplemental eNOS cofactors.

CONCLUSION

Together, our findings strongly indicate that RE mediates RIPC by limiting eNOS uncoupling and mitigates myocardial IR injury.

Targeted inhibition of RAGE in substantia nigra of rats blocks 6-OHDA-induced dopaminergic denervation

The receptor for advanced glycation endproducts (RAGE) is a pattern-recognition receptor associated with inflammation in most cell types. RAGE up-regulates the expression of proinflammatory mediators and its own expression via activation of NF-kB. Recent works have proposed a role for RAGE in Parkinson's disease (PD). In this study, we used the multimodal blocker of RAGE FPS-ZM1, which has become available recently, to selectively inhibit RAGE in the substantia nigra (SN) of rats intracranially injected with 6-hydroxydopamine (6-OHDA). FPS-ZM1 (40 μg per rat), injected concomitantly with 6-OHDA (10 μg per rat) into the SN, inhibited the increase in RAGE, activation of ERK1/2, Src and nuclear translocation of NF-kB p65 subunit in the SN. RAGE inhibition blocked glial fibrillary acidic protein and Iba-1 upregulation as well as associated astrocyte and microglia activation. Circulating cytokines in serum and CSF were also decreased by FPS-ZM1 injection. The loss of tyrosine hydroxylase and NeuN-positive neurons was significantly inhibited by RAGE blocking. Finally, FPS-ZM1 attenuated locomotory and exploratory deficits induced by 6-OHDA. Our results demonstrate that RAGE is an essential component in the neuroinflammation and dopaminergic denervation induced by 6-OHDA in the SN. Selective inhibition of RAGE may offer perspectives for therapeutic approaches.

Vitamin A Oral Supplementation Induces Oxidative Stress and Suppresses IL-10 and HSP70 in Skeletal Muscle of Trained Rats

Exercise training intensity is the major variant that influences the relationship between exercise, redox balance, and immune response. Supplement intake is a common practice for oxidative stress prevention; the effects of vitamin A (VA) on exercise training are not yet described, even though this molecule exhibits antioxidant properties. We investigated the role of VA supplementation on redox and immune responses of adult Wistar rats subjected to swimming training. Animals were divided into four groups: sedentary, sedentary + VA, exercise training, and exercise training + VA. Over eight weeks, animals were submitted to intense swimming 5 times/week and a VA daily intake of 450 retinol equivalents/day. VA impaired the total serum antioxidant capacity acquired by exercise, with no change in interleukin-1β and tumor necrosis factor-α levels. In skeletal muscle, VA caused lipid peroxidation and protein damage without differences in antioxidant enzyme activities; however, Western blot analysis showed that expression of superoxide dismutase-1 was downregulated, and upregulation of superoxide dismutase-2 induced by exercise was blunted by VA. Furthermore, VA supplementation decreased anti-inflammatory interleukin-10 and heat shock protein 70 expression, important factors for positive exercise adaptations and tissue damage prevention. Our data showed that VA supplementation did not confer any antioxidative and/or protective effects, attenuating exercise-acquired benefits in the skeletal muscle.

Chemical composition, antinociceptive, anti-inflammatory and redox properties in vitro of the essential oil from Remirea maritima Aubl. (Cyperaceae)

BACKGROUND

The present study was carried out to evaluate antioxidant, antinociceptive and anti-inflammatory activities of essential oil from R. maritima (RMO) in experimental protocols.

METHODS

The essential oil from the roots and rhizomes of RMO were obtained by hydrodistillation using a Clevenger apparatus, and analyzed by gas chromatography/mass spectrometry (GC/MS). Here, we evaluated free radical scavenging activities and antioxidant potential of RMO using in vitro assays for scavenging activity against hydroxyl radicals, hydrogen peroxide, superoxide radicals, and nitric oxide. The total reactive antioxidant potential (TRAP) and total antioxidant reactivity (TAR) indexes and in vitro lipoperoxidation were also evaluated. The ability of RMO to prevent lipid peroxidation was measured by quantifying thiobarbituric acid-reactive substances (TBARS). NO radical generated at physiological pH was found to be inhibited by RMO, that showed scavenging effect upon SNP-induced NO production at all concentrations. Antinociceptive and anti-inflammatory properties were evaluated by acetic acid writhing reflex, Formalin-induced nociception and Carrageenan-induced edema test.

RESULTS

The majors compounds identified was remirol (43.2%), cyperene (13.8%), iso-evodionol (5.8%), cyperotundone (5.7%), caryophyllene oxide (4.9%), and rotundene (4.6%). At the TRAP assay, RMO concentration of 1 mg.mL(-1) showed anti-oxidant effects and at concentration of 1 and 10 ng.mL(-1) RMO showed pro-oxidant effect. RMO at 1 mg.mL(-1) also showed significant anti-oxidant capacity in TAR measurement. Concentrations of RMO from 1 ng.mL(-1) to 100 μg.mL(-1) enhanced the AAPH-induced lipoperoxidation. RMO reduced deoxyribose oxidative damage, induced by the Fenton reaction induction system, at concentrations from 1 ng.mL(-1) to 100 μg.mL(-1). We observed that RMO caused a significant increase in rate of adrenaline auto-oxidation. On the other hand RMO did not present any scavenging effect in H2O2 formation in vitro. The results of this study revealed that RMO has both peripheral and central analgesic properties. The RMO, all doses, orally (p.o.) administered significantly inhibited (p < 0.05, p < 0.01 and p < 0.001) the acetic acid-induced writhings and two phases of formalin-induced nociception in mice.

CONCLUSION

The RMO demonstrated antioxidant and analgesic profile which may be related to the composition of the oil.

Preventive supplementation with fresh and preserved peach attenuates CCl4-induced oxidative stress, inflammation and tissue damage

The present study was elaborated to comparatively evaluate the preventive effect of different peach-derived products obtained from preserved fruits (Syrup and Preserve Pulp Peach [PPP]) and from fresh peels and pulps (Peel and Fresh Pulp Peach [FPP]) in a model of liver/renal toxicity and inflammation induced by carbon tetrachloride (CCl4) in rats. Tissue damage (carbonyl, thiobarbituric acid reactive species and sulfhydril), antioxidant enzymes activity (catalase and superoxide dismutase) and inflammatory parameters [tumor necrosis factor (TNF)-α and interleukin (IL)-1β levels, and receptor for advanced glycation end-products (RAGE) and nuclear factor (NF)κB-p65 immunocontent] were investigated. Our findings demonstrated that Peel, PPP and FPP (200 or 400 mg/kg) daily administration by oral gavage for 30 days conferred a significant protection against CCl4-induced antioxidant enzymes activation and, most importantly, oxidative damage to lipids and proteins as well as blocked induction of inflammatory mediators such as TNF-α, IL-1β, RAGE and NFκB. This antioxidant/anti-inflammatory effect seems to be associated with the abundance of carotenoids and polyphenols present in peach-derived products, which are enriched in fresh-fruit-derived preparations (Peel and FPP) but are also present in PPP. The Syrup - which was the least enriched in antioxidants - displayed no protective effect in our experiments. These effects cumulated in decreased levels of transaminases and lactate dehydrogenase leakage into serum and maintenance of organ architecture. Therefore, the herein presented results show evidence that supplementation with peach products may be protective against organ damage caused by oxidative stress, being interesting candidates for production of antioxidant-enriched functional foods.

Effects of different products of peach (Prunus persica L. Batsch) from a variety developed in southern Brazil on oxidative stress and inflammatory parameters in vitro and ex vivo

Antioxidant, anti-glycation and anti-inflammatory activities of fresh and conserved peach fruits (Prunus persica L. Batsch) were compared. Fresh peach pulps, peels, preserve peach pulps and the preserve syrup were prepared at equal concentrations. Rat liver, kidney and brain cortex tissue slices were pre-incubated with peach samples, subjected to oxidative stress with FeSO₄ and hydrogen peroxide. Fresh peach pulps and peel conferred higher protection against cytotoxicity and oxidative stress than preserve peach pulps in most tissues. Release of tumor necrosis factor-α and interleukin-1β was also significantly decreased by Fresh peach pulps and peel, followed by preserve peach pulps. Total phenolic determination and HPLC analysis of carotenoids showed that the content of secondary metabolites in Fresh peach pulps and peel is significantly higher than in preserve peach pulps, while the syrup had only small or trace amounts of these compounds. Fresh peach pulps and Peel demonstrated high antioxidant and anti-inflammatory effects preventing against induced damage.

Redox properties of Abarema cochliacarpos (Gomes) Barneby & Grime (Fabaceae) stem bark ethanol extract and fractions

The redox properties of the hydroethanol extract (EE) and its ethyl acetate (EAF) and hydromethanol (HMF) fractions obtained from Abarema cochliacarpos (Gomes) Barneby & Grimes stem bark were evaluated. EAF had the highest total phenol content (848.62 ± 78.18 mg g⁻¹), while EE showed the highest content of catechin (71.2 µg g⁻¹). EE, EAF and HMF exhibited the highest levels of antioxidant activity at 100 and 1000 µg mL⁻¹ when the non-enzymatic antioxidant potential was evaluated by the total reactive antioxidant potential, total antioxidant reactivity and nitric oxide scavenging assays. In addition, EAF and HMF showed SOD-like activity. The results for EE, EAF and HMF in this study showed that A. cochliacarpos (Gomes) Barneby & Grimes stem bark have redox properties and may be able to help the endogenous enzymatic and non-enzymatic systems to keep the redox balance.

Redox characterization of usnic acid and its cytotoxic effect on human neuron-like cells (SH-SY5Y)

Usnic acid (UA) is the most common and abundant lichenic secondary metabolite with potential therapeutic application. Anti-inflammatory and antitumour properties have already been reported and UA-enriched extracts are widely used to treat several diseases in the folk medicine. First, we performed in silico evaluation of UA interactions with genes/proteins and important compounds for cellular redox balance and NO pathway. Then, we assessed UA redox properties against different reactive species (RS) generated in vitro, and evaluated its action on SH-SY5Y neuronal like cells upon hydrogen peroxide (H(2)O(2)), since no in vitro neurotoxicological data has been reported so far. Total reactive antioxidant potential index (TRAP) showed a significant antioxidant capacity of UA at the highest tested concentration; UA was also effective against hydroxyl radicals and reduced the formation of nitric oxide. In vitro, lipoperoxidation was enhanced by UA and changed the cellular viability at highest concentration of 20μg/mL for 1 and 4h, as well as 2 and 20μg/mL for 24h of treatment, according to MTT reduction assay. Moreover, UA did not display protective effects against H(2)O(2)-induced cell death in any case. Evaluation of intracellular RS production by the DCFH-based assay indicated that UA was able to induce changes in basal RS production at concentration of 20μg/mL for 1h and from 2ng/mL to 20μg/mL for 4 and 24h. In conclusion, UA could display variable redox-active properties, according to different system conditions and/or cellular environment. Moreover, our results suggest that potential neurotoxicological effects of UA should be further studied by additional approaches; for instance, in vivo and clinical studies.