Retinol and retinoic acid increase MMP-2 activity by different pathways in cultured Sertoli cells

Cross-sectional assessment of the ellipsoid zone and the retinal pigment epithelium-Bruch membrane complex after systemic isotretinotin use

PURPOSE

To evaluate the cross-sectional areas of the retinal pigment epithelium-Bruch membrane complex (RPE-B) and ellipsoid zon (EZ) and the thickness of the macula, retinal nerve fibre layer (RNFL), and ganglion cell-inner plexiform layer (GC-IPL) in patients using short-term systemic isotretinoin.

METHOD

A total of 43 right eyes of 43 patients treated with systemic isotretinoin for acne vulgaris were included in this prospective study. Macula, GC-IPL, RNFL thicknesses and central cross-sectional EZ and RPE-B areas were evaluated with optical coherence tomography (Zeiss, Cirrus HD OCT 5000) prior to treatment and in first, second and third months after the onset of isotretinoin treatment. For the measurement of EZ and RPE-B area, foveal EDI-OCT scans were binarized by using the public domain software ImageJ 1.51 s.

RESULTS

Mean duration of isotretinoin treatment was 77 ± 15 days and mean dose was 2228 ± 574 milligrams. There was a statistically significant increment in central cross-sectional EZ and RPE-B areas in each follow-up examination, when analysed by repeated measurement analysis (p:0.002 and p:0.006, respectively). There was no correlation between total isotretinoin dose and the difference between final and basal EZ and RPE-B areas (p > 0.05, for both). When repeated measurements in follow-up examinations were compared, GC-IPL thicknesses except the superotemporal region (p:0.040) and RNFL thicknesses did not show a significant difference (p > 0.05). There was not any significant relation between total isotretinoin dose and 3rd month and basal measurement differences in macula, GC-IPL and RNFL thicknesses in any area (p > 0.05, for all).

CONCLUSION

There has been an increase in the area of RPE-B and EZ with short-term use of isotretinoin therapy. Future studies examining the relationship between functional tests and the RPE-B and EZ areas may provide more in-depth information on the effects of isotretinoin in the eye.

Evaluation of musculoskeletal adverse effects in patients on systemic isotretinoin treatment: A cross-sectional study

Objectives

This study aims to investigate the frequency of musculoskeletal adverse effects in acne vulgaris patients receiving systemic isotretinoin treatment.

Patients and methods

Between January 2016 and December 2017, a total of 200 severe acne patients (22 males, 178 females; mean age: 21.8±0.4 years; range, 15 to 53 years) who were on isotretinoin treatment were retrospectively analyzed. Data including age, sex, body mass index (BMI), duration of disease, diagnosis, and comorbidities were recorded. Back pain severity was evaluated with the Visual Analog Scale (VAS).

Results

The treatment period was mean 8.5±0.1 (range, 6 to 12) months. The dose of isotretinoin was mean 0.6±0.1 (range, 0.5 and 1) mg/kg. Musculoskeletal side effects were seen in 99 (49.5%) patients. Back pain was reported during the treatment period in 78 (78.7%) patients. The diagnosis was mechanical back pain in 31 (39.7%) and inflammatory back pain in 47 (60.3%) patients. The moderate-severe back pain group received higher cumulative isotretinoin doses than the mild back pain group (p=0.003). The BMI values did not show a significant difference between the patients with and without back pain (p=0.55). There was no significant correlation between the BMI and VAS scores (p=0.06). The VAS scores were found to be correlated with age (p=0.04). Sacroiliitis was diagnosed in four (4%) patients. One (1%) patient was diagnosed with enthesitis. Creatine kinase elevation was reported in 18 (18.1%) patients, while three (3%) patients described myalgia of mild severity.

Conclusion

Low back pain is one of the most common musculoskeletal side effects of isotretinoin treatment that usually resolves with dose reduction. The cumulative dose of isotretinoin does not seem to play a role in the development of back pain, but can determine pain severity. Pain severity is directly correlated with the increasing age. Evaluation of the patients for musculoskeletal side effects during isotretinoin use is important in clinical practice, as it is a common occurrence.

Liver X Receptor Expression and Pentraxin 3 Production in Chronic Rhinosinusitis and Sinonasal Mucosal Fibroblast Cells

The long pentraxin 3 (PTX3) is a prototypic molecule for recognizing pathogens. Liver X receptors (LXRs), belonging to nuclear receptors (NRs) for cholesterol metabolism through heterodimerizing with other NRs, were recently reported to participate in inflammation. However, their roles in chronic rhinosinusitis without nasal polyps (CRSsNP) are unclear. Therefore, this study was sought to explore roles of LXRs in chronic rhinosinusitis (CRS) sinonasal tissues and derived fibroblasts. Immunohistochemistry indicated that LXRα and β expression and lipid/fat deposition were differentially expressed in the control and CRSsNP nasal mucosa. GW7647 (a peroxisome proliferator activated receptor α (PPARα) agonist) and GW3965 (a dual agonist for LXRα and β) significantly caused PTX3 induction in the fibroblast cells. GW3965 induced PTX3 mRNA and protein expression, and the induction substantially led to PTX3 secretion. Meanwhile, an endogenous agonist-cholesterol had a similar enhancing effect on the induction of PTX3 protein. LXR siRNA knockdown to lower LXRα or β expression significantly compromised PTX3 induction. Interestingly, GW3965 also induced phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) activation and its inhibition reduced PTX3 expression. Collectively, we demonstrated here for the first time that CRSsNP nasal mucosa differentially expresses LXRα and β and deposits lipids/fats that may contain cholesterol metabolites to activate LXRs. Activation of LXRs leads to PTX3 production in sinonasal mucosa-derived fibroblasts. Our previous study showed PTX3 overexpression in the nasal cavity of CRSsNP, whereas this study highlights that cholesterol metabolites and LXR activation regulate PTX3 production and may contribute to antimicrobial activity and tissue repair during CRSsNP progression.

SAPHO syndrome: the supposed trigger by isotretinoin, the efficacy of adalimumab and the specter of depressive disorder: a case report

Background

SAPHO (synovitis, acne, pustolosis, hyperostosis and osteitis) syndrome is a rare autoinflammatory chronic disorder, presenting with non-infectious osteitis, sterile joint inflammation and skin manifestations including palmoplantar pustolosis and severe acne.

It could be often misdiagnosed for its heterogeneous clinical presentation. Treatment is challenging and, due to the rarity of this syndrome, no randomized controlled clinical trials have been conducted. Empirical treatments, including non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroids, antibiotics and bisphosphonates and disease-modifying anti-rheumatic drugs (DMARDs) could be quite effective. Anti-tumor necrosis factor-alpha (anti-TNF-α) agents and interleukin-1 (IL-1) antagonists have shown promising results in refractory patients. Isotretinoin, commonly used for severe acne, has been rarely described as possible trigger of osteo-articular manifestations, in particular sacroiliitis.

Case presentation

The case of a boy, affected by acne fulminans and depression, who presented with sacroiliitis after a 10-week treatment with isotretinoin is presented. After SAPHO diagnosis, NSAIDs therapy was started but the onset of bilateral gluteal hidradenitis suppurativa required the switch to a TNF-α antagonist (Adalimumab) with the achievement of a good control of the disease. Despite specific therapy with sertraline, the patient continued to complains severe depression.

Conclusions

Our case reports a temporal association between the onset of osteo-articular symptoms and the introduction of isotretinoin, as previously described. However, this timeline is not sufficient to establish a causal role of this drug into the pathogenesis of sacroiliitis. At this regard, further studies are required. The occurrence of hidradenitis suppurativa during SAPHO course supported the introduction of TNF-α blockers with a favourable result, as reported in a few cases in literature. The association between SAPHO syndrome and depressive mood disorders is already reported. Our patient experienced severe depression whose trend seems to be independent from the course of the main disease. Currently, it is not clarified if depression could be considered reactive to the underling disease or if it forms an integral part of the autoinflammatory disorder.

Drug-induced maculopathy

PURPOSE OF REVIEW

The purpose of this article is to provide an overview of drug-induced maculopathies including their clinical presentations, diagnostic findings, and treatment options. With the increasing pace of development and arrival of drugs to the market, this review aims to inform retina specialists of relevant side effects that may be encountered in a clinical practice setting.

RECENT FINDINGS

The major themes visited in this article focus on relevant findings of drugs that cause pigmentary and crystalline maculopathy, photoreceptor dysfunction, cystoid macular edema, central serous choroidopathy, uveitis, and vascular damage.

SUMMARY

The current review reports updated findings and discusses the pathophysiologic mechanisms, presentations, and treatments of drug-induced maculopathies.

Inhibition of testicular embryonal carcinoma cell tumorigenicity by peroxisome proliferator-activated receptor-β/δ- and retinoic acid receptor-dependent mechanisms

Peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) has important physiological functions in control of cell growth, lipid and glucose homeostasis, differentiation and inflammation. To investigate the role of PPARβ/δ in cancer, stable human testicular embryonal carcinoma cell lines were developed that constitutively express PPARβ/δ. Expression of PPARβ/δ caused enhanced activation of the receptor, and this significantly decreased proliferation, migration, invasion, anchorage-independent growth, and also reduced tumor mass and volume of ectopic xenografts derived from NT2/D1 cells compared to controls. The changes observed in xenografts were associated with decreased PPARβ/δ-dependent expression of proliferating cell nuclear antigen and octamer-binding transcription factor-3/4, suggesting suppressed tumor proliferation and induction of differentiation. Inhibition of migration and invasion was mediated by PPARβ/δ competing with formation of the retinoic acid receptor (RAR)/retinoid X receptor (RXR) complex, resulting in attenuation of RARα-dependent matrix metalloproteinase-2 expression and activity. These results demonstrate that PPARβ/δ mediates attenuation of human testicular embryonal carcinoma cell progression through a novel RAR-dependent mechanism and suggest that activation of PPARβ/δ inhibits RAR/RXR dimerization and represents a new therapeutic strategy.

Effects of all-trans retinoic acid, retinol, and β-carotene on murine macrophage activity

Previous studies have demonstrated that vitamin A and carotenoids regulate immune function in lymphocytes and splenocytes, and that the carotenoid lutein regulates matrix metalloproteinase-9 (MMP-9) production in macrophages. In this study, we investigated the effects of all-trans retinoic acid (atRA, a bioactive vitamin A metabolite), retinol (vitamin A), and β-carotene (vitamin A precursor) on the activity of murine RAW264.7 and peritoneal macrophages. Our results indicated that atRA and retinol could induce GM-CSF and IL-16 expression, whereas all these tested substances enhanced MMP-9 production. Interestingly, the expression of GM-CSF, IL-16, and MMP-9 was distinctly regulated by these three substances. AtRA and retinol affected GM-CSF and IL-16 expression mainly through RA receptor β (RARβ). However, atRA induced MMP-9 production was via RARα activation and retinol and β-carotene caused MMP-9 production via RARα and β activation. These were supported by the observations that the RARα and β agonists/antagonists differentially affected MMP-9 production and that atRA and β-carotene enhanced RARE-mediated and MMP-9 promoter luciferase activity. In parallel, while the MMP-9 induction by atRA was not affected by the MAPKs inhibitors, its induction by retinol and β-carotene was repressed by the inhibitor targeting ERK1/2. Finally, we show that all the tested substances could functionally enhance macrophage phagocytosis. Taken together, we provide evidence here for the first time that atRA, retinol, and β-carotene differentially regulate GM-CSF, IL-16, and MMP-9 production in macrophages, explaining at least in part why these vitamin A-related substances are beneficial for immunity.

Inhibition of matrix metalloproteinases expression in human dental pulp cells by all-trans retinoic acid

All-trans retinoic acid (ATRA) inhibits matrix metalloproteinase (MMP)-2 and MMP-9 in synovial fibroblasts, skin fibroblasts, bronchoalveolar lavage cells and cancer cells, but activates MMP-9 in neuroblast and leukemia cells. Very little is known regarding whether ATRA can activate or inhibit MMPs in human dental pulp cells (HDPCs). The purpose of this study was to determine the effects of ATRA on the production and secretion of MMP-2 and -9 in HDPCs. The productions and messenger RNA (mRNA) expressions of MMP-2 and -9 were accessed by gelatin zymography and real-time polymerase chain reaction (PCR), respectively. ATRA was found to decrease MMP-2 level in a dose-dependent manner. Significant reduction in MMP-2 mRNA expression was also observed in HDPCs treated with 25 µmol⋅L(-1) ATRA. However, HDPCs treated with ATRA had no effect on the pattern of MMP-9 produced or secreted in either cell extracts or conditioned medium fractions. Taken together, ATRA had an inhibitory effect on MMP-2 expression in HDPCs, which suggests that ATRA could be a candidate as a medicament which could control the inflammation of pulp tissue in vital pulp therapy and regenerative endodontics.

The carotenoid lutein enhances matrix metalloproteinase-9 production and phagocytosis through intracellular ROS generation and ERK1/2, p38 MAPK, and RARβ activation in murine macrophages

Carotenoid lutein causes MMP-9 release that participates in macrophage phagocytosis.

Early studies have demonstrated the ability of dietary carotenoids to enhance immune response, but the mechanism underlying their influence on macrophage activity remains unclear. Here, we investigated the effects of carotenoids on macrophage activity. Carotenoids, including lutein and lycopene, enhanced MMP-9 activity in RAW264.7 macrophages. Lutein was chosen as a representative and analyzed further in this study. It increased the synthesis, activity, and release of MMP-9 in murine RAW264.7 and primary-cultured peritoneal macrophages. MMP-9 induction by lutein was through the transcriptional regulation of mmp-9. It was blunted by the MAPK inhibitors targeting ERK1/2 and p38 MAPK, the reagents that inhibit free radical signaling, and the inhibitors and siRNA targeting RARβ. Moreover, lutein induced Nox activation and intracellular ROS production at an early stage of treatment. This carotenoid also caused ERK1/2 and p38 MAPK activation, RARβ expression, and RAR interaction with its responsive element in the promoter region. These findings suggest the involvement of ROS, MAPKs, and RARβ activation in lutein-driven MMP-9 expression and release. Interestingly, lutein enhanced the phagocytic activity of macrophages, and the secreted MMP-9 appeared to be involved in this process. In summary, we provide evidence here for the first time that the carotenoid lutein induces intracellular ROS generation and MAPK and RARβ activation in macrophages, leading to an increase in MMP-9 release and macrophage phagocytosis. Our results demonstrate that lutein exerts an immunomodulatory effect on macrophages.

Sacroiliitis secondary to isotretinoin

Reported is the case of a 17-year old male with sacroiliitis confirmed by magnetic resonance imaging (MRI) while undergoing isotretinoin treatment for acne vulgaris. The cessation of isotretinoin and symptomatic treatment resolved the symptoms within 6 weeks, with no signs of sacroiliitis on repeat MRI 10 months later. The temporal association of disease onset and commencement of isotretinoin along with rapid recovery on withdrawal supports the role of isotretinoin in this case.

Bioinformatical and in vitro approaches to essential oil-induced matrix metalloproteinase inhibition

CONTEXT

Essential oils carry diverse antimicrobial and anti-enzymatic properties.

OBJECTIVE

Matrix metalloproteinase (MMP) inhibition characteristics of Salvia fruticosa Miller (Labiatae), Myrtus communis Linnaeus (Myrtaceae), Juniperus communis Linnaeus (Cupressaceae), and Lavandula stoechas Linnaeus (Labiatae) essential oils were evaluated.

MATERIALS AND METHODS

Chemical compositions of the essential oils were analyzed by gas chromatography-mass spectrometry (GC-MS). Bioinformatical database analysis was performed by STRING 9.0 and STITCH 2.0 databases, and ViaComplex software. Antibacterial activity of essential oils against periodontopathogens was tested by the disc diffusion assay and the agar dilution method. Cellular proliferation and cytotoxicity were determined by commercial kits. MMP-2 and MMP-9 activities were measured by zymography.

RESULTS

Bioinformatical database analyses, under a score of 0.4 (medium) and a prior correction of 0.0, gave rise to a model of protein (MMPs and tissue inhibitors of metalloproteinases) vs. chemical (essential oil components) interaction network; where MMPs and essential oil components interconnected through interaction with hydroxyl radicals, molecular oxygen, and hydrogen peroxide. Components from L. stoechas potentially displayed a higher grade of interaction with MMP-2 and -9. Although antibacterial and growth inhibitory effects of essential oils on the tested periodontopathogens were limited, all of them inhibited MMP-2 in vitro at concentrations of 1 and 5 µL/mL. Moreover, same concentrations of M. communis and L. stoechas also inhibited MMP-9. MMP-inhibiting concentrations of essential oils were not cytotoxic against keratinocytes.

DISCUSSION AND CONCLUSION

We propose essential oils of being useful therapeutic agents as MMP inhibitors through a mechanism possibly based on their antioxidant potential.

Retinol induces morphological alterations and proliferative focus formation through free radical-mediated activation of multiple signaling pathways

AIM

Toxicity of retinol (vitamin A) has been previously associated with apoptosis and/or cell malignant transformation. Thus, we investigated the pathways involved in the induction of proliferation, deformation and proliferative focus formation by retinol in cultured Sertoli cells of rats.

METHODS

Sertoli cells were isolated from immature rats and cultured. The cells were subjected to a 24-h treatment with different concentrations of retinol. Parameters of oxidative stress and cytotoxicity were analyzed. The effects of the p38 inhibitor SB203580 (10 μmol/L), the JNK inhibitor SP600125 (10 μmol/L), the Akt inhibitor LY294002 (10 μmol/L), the ERK inhibitor U0126 (10 μmol/L) the pan-PKC inhibitor Gö6983 (10 μmol/L) and the PKA inhibitor H89 (1 μmol/L) on morphological and proliferative/transformation-associated modifications were studied.

RESULTS

Retinol (7 and 14 μmol/L) significantly increases the reactive species production in Sertoli cells. Inhibition of p38, JNK, ERK1/2, Akt, and PKA suppressed retinol-induced [(3)H]dT incorporation into the cells, while PKC inhibition had no effect. ERK1/2 and p38 inhibition also blocked retinol-induced proliferative focus formation in the cells, while Akt and JNK inhibition partially decreased focus formation. ERK1/2 and p38 inhibition hindered transformation-associated deformation in retinol-treated cells, while other treatments had no effect.

CONCLUSION

Our results suggest that activation of multiple kinases is responsible for morphological and proliferative changes associated to malignancy development in Sertoli cells by retinol at the concentrations higher than physiological level.

Vitamin A (retinol) up-regulates the receptor for advanced glycation endproducts (RAGE) through p38 and Akt oxidant-dependent activation

Retinol (vitamin A) is believed to exert preventive/protective effects against malignant, neurodegenerative and cardiovascular diseases by acting as an antioxidant. However, later clinical and experimental data show a pro-oxidant action of retinol and other retinoids at specific conditions. The receptor for advanced glycation endproducts (RAGE) is a pattern recognition receptor, being activated by different ligands such as S100 proteins, HMGB1 (amphoterin), β-amyloid peptide and advanced glycation endproducts (AGE). RAGE activation influences a wide range of pathological conditions such as diabetes, pro-inflammatory states and neurodegenerative processes. Here, we investigated the involvement of different mitogen-activated protein kinases (MAPK: ERK1/2, p38 and JNK), PKC, PKA and Akt in the up-regulation of RAGE by retinol. As previously reported, we observed that the increase in RAGE immunocontent by retinol is reversed by antioxidant co-treatment, indicating the involvement of oxidative stress in this process. Furthermore, the p38 inhibitor SB203580 and the Akt inhibitor LY294002 also decreased the effect of retinol on RAGE levels, suggesting the involvement of these protein kinases in such effect. Both p38 and Akt phosphorylation were increased by treatment with pro-oxidant concentrations of retinol, and the antioxidant co-treatment blocked this effect, indicating that activation of p38 and Akt during retinol treatment is dependent on reactive species production. The 2',7'-dichlorohydrofluorescein diacetate (DCFH) assay also indicated that retinol treatment enhances cellular reactive species production. Altogether, these data indicate that RAGE up-regulation by retinol is mediated by the free radical-dependent activation of p38 and Akt.

Spermiation: The process of sperm release

Spermiation is the process by which mature spermatids are released from Sertoli cells into the seminiferous tubule lumen prior to their passage to the epididymis. It takes place over several days at the apical edge of the seminiferous epithelium, and involves several discrete steps including remodelling of the spermatid head and cytoplasm, removal of specialized adhesion structures and the final disengagement of the spermatid from the Sertoli cell. Spermiation is accomplished by the co-ordinated interactions of various structures, cellular processes and adhesion complexes which make up the "spermiation machinery". This review addresses the morphological, ultrastructural and functional aspects of mammalian spermiation. The molecular composition of the spermiation machinery, its dynamic changes and regulatory factors are examined. The causes of spermiation failure and their impact on sperm morphology and function are assessed in an effort to understand how this process may contribute to sperm count suppression during contraception and to phenotypes of male infertility.

Retinoids regulate human amniotic tissue-type plasminogen activator gene by a two-step mechanism

The collagenolytic effects of the tissue-type plasminogen activator (t-PA) leading to extracellular matrix degradation are clearly involved in the physiopathology of human foetal membranes rupture. Nevertheless, the regulation of t-PA gene expression in extraembryonic developmental contexts remains unknown. The aim of our study is to propose the retinoic acids (RAs) as molecular regulators of t-PA expression in foetal membranes. RA induced t-PA mRNA and proteins in a time-dependent manner in amniotic membrane explants and Wistar Institute Susan Hayflick (WISH) cells. Furthermore, the use of cycloheximide revealed a two-step regulation of t-PA gene. Gene reporter assays confirmed that the RA-induced t-PA gene expression occurred through interactions of retinoid receptors (RARs and RXRs) with a DR5 response element located at –7 kb from the transcription site. Site-directed mutagenesis of this region of the t-PA promoter showed that SP1 factor was also retinoid-mediated induction, and immunoprecipitation assays revealed that SP1 and RAR/RXR interacted physically. Chromatin immunoprecipitation demonstrated that interactions between RARs, RXRs and t-PA promoter were time dependent: RAR-α/RXR-α bound DR5 motif before and up to 12 hrs of RA exposure, and RAR-β/RXR-α bound DR5 response element after 12 hrs of RA treatment. Finally, experiments using shRNA and RAR-β-specific antagonist revealed that reducing RAR-β induction decreased t-PA induction. Altogether, our results established that the RA-mediated regulation of t-PA in human foetal membranes occurred through two steps, with a major role played by RAR-β.

The NF kappa B-mediated control of RS and JNK signaling in vitamin A-treated cells: duration of JNK-AP-1 pathway activation may determine cell death or proliferation

Nuclear factor kappa B (NFkappaB) has emerged as a crucial regulator of cell survival, playing important functions in cellular resistance to oxidants and chemotherapeutic agents. Recent studies showed that NFkappaB mediates cell survival through suppression of the accumulation of reactive species (RS) and a control of sustained activation of the Jun-N-terminal kinase (JNK) cascade. This work was undertaken in order to evaluate the role of NFkappaB in modulating the pro-oxidant effects of supplementation with vitamin A (retinol, ROH) in Sertoli cells, a major ROH physiological target. In this work, we reported that ROH treatment increases mitochondrial RS formation leading to a redox-dependent activation of NFkappaB. NFkappaB activation played a pivotal role in counteract RS accumulation in ROH-treated cells, since NFkappaB inhibition with DNA decoy oligonucleotides or pharmacological inhibitors (BAY-117082) potentiated ROH-induced RS accumulation and oxidative damage. In the presence of NFkappaB inhibition, ROH-induced oxidative stress promoted a prolonged activation of the JNK-activator protein 1 (AP-1) pathway and induced significant decreases in cell viability. Inhibition of JNK-AP-1 with decoy oligonucleotides to AP-1 or JNK inhibitor SP600125 prevented the decreases in cell viability. Antioxidants blocked the persistent JNK-AP-1 activation, cell oxidative damage, and the decreases in cell viability induced by NFkappaB inhibition. Finally, our data point superoxide dismutase (SOD)2 as a potential antioxidant factor involved in NFkappaB protective effects against ROH-induced oxidative stress. Taken together, data presented here show that NFkappaB mediates cellular resistance to the pro-oxidant effects of vitamin A by inhibiting RS accumulation and the persistent and redox-dependent activation of JNK-AP-1 cascade.

Xanthine oxidase-dependent ROS production mediates vitamin A pro-oxidant effects in cultured Sertoli cells

Several studies have suggested that vitamin A (retinol, ROH) presents pro-oxidant properties in biological systems. Recent studies point out that xantine oxidase, a ROS-generating enzyme, catalyses ROH oxidation to RA in vitro. These works stimulated the authors to investigate whether xanthine oxidase could be involved on the ROH pro-oxidative effects reported in cultured Sertoli cells. In vitro, it was demonstrate that xanthine oxidase generates superoxide in the presence of ROH as assessed by superoxide mediated-NBT reduction. Superoxide production is potentiated in the presence of NADH and inhibited by allopurinol. In Sertoli cells, ROH treatment increased xanthine oxidase activity and inhibition of the enzyme with allopurinol attenuated ROH-induced ROS production, protein damage and cytotoxicity. Moreover, inhibition of ROH oxidation to RA by retinaldehyde dehydrogenase inhibitor potentiated both xanthine oxidase-dependent ROS production and cell damage in ROH-treated cells. The data show that xanthine oxidase may play a role on vitamin A pro-oxidant effects.

Retinol up-regulates the receptor for advanced glycation endproducts (RAGE) by increasing intracellular reactive species

Retinol (vitamin A) and other retinoids have been suggested to exert an important antioxidant function in biological systems, besides their more established role as regulators of cell growth and differentiation. On the other hand, many authors have recently observed pro-oxidant activities of vitamin A and other retinoids in vitro and in vivo, resulting in cell death and/or transformation associated to increased oxidative damage. However, the mechanisms by which retinol causes oxidative stress are still not fully understood. Receptors for advanced glycation endproducts (RAGE) have been recently implied as promoters and/or amplifiers of oxidant-mediated cell death induced by diverse agents, and increased RAGE expression is observed in conditions related to unbalanced production of reactive species, such as in atherosclerosis and neurodegeneration. In the present work, we observed that retinol supplementation increases RAGE protein expression in cultured Sertoli cells, and antioxidant co-treatment reversed this effect. Retinol-increased RAGE expression was observed only at concentrations that induce intracellular reactive species production, as assessed by the DCFH assay. These results indicate that retinol is able to increase RAGE expression by an oxidant-dependent mechanism, and suggest that RAGE signaling may be involved in some of the deleterious effects observed in some retinol-supplementation therapies.