Arianna Romani

Hypoxia induces cell damage via oxidative stress in retinal epithelial cells

Abstract Retinal diseases (RD), including diabetic retinopathy, are among the most important eye diseases in industrialized countries. RD is characterized by abnormal angiogenesis associated with an increase in cell proliferation and apoptosis. Hypoxia could be one of the triggers of the pathogenic mechanism of this disease. A key regulatory component of the cells hypoxia response system is hypoxia-inducible factor 1 alpha (HIF-1α). It has been demonstrated that the induction of HIF-1α expression can be also achieved in vitro by exposure with cobalt chloride (CoCl2), leading to an intracellular hypoxia-like state. In this study we have investigated the effects of CoCl2 on human retinal epithelium cells (hRPE), which are an integral part of the blood–retinal barrier, with the aim to determine the possible role of oxidative stress in chemical hypoxia-induced damage in retinal epithelial cells. Our data showed that CoCl2 treatment is able to induce HIF-1α expression, that parallels with the formation of reactive oxygen species (ROS) and the increase of lipid 8-isoprostanes and 4-hydroxynonenal (4-HNE) protein adducts levels. In addition we observed the activation of the redox-sensitive transcription factor nuclear factor-kappaB (NFkB) by CoCl2 which can explain the increased levels of vascular endothelial growth factor (VEGF). The increased number of dead cells seems to be related to an apoptotic process. Taken together these evidences suggest that oxidative stress induced by hypoxia might be involved in RD development through the stimulation of two key-events of RD such as neo-angiogenesis and apoptosis.

Oxidative Stress and Bone Resorption Interplay as a Possible Trigger for Postmenopausal Osteoporosis

The underlying mechanism in postmenopausal osteoporosis (PO) is an imbalance between bone resorption and formation. This study was conducted to investigate whether oxidative stress (OxS) might have a role in this derangement of bone homeostasis. In a sample of 167 postmenopausal women, we found that increased serum levels of a lipid peroxidation marker, hydroperoxides, were negatively and independently associated with decreased bone mineral density (BMD) in total body (r = −0.192, P < 0.05), lumbar spine (r = −0.282, P < 0.01), and total hip (r = −0.282, P < 0.05), as well as with increased bone resorption rate (r = 0.233, P < 0.05), as assessed by the serum concentration of C-terminal telopeptide of type I collagen (CTX-1). On the contrary, the OxS marker failed to be correlated with the serum levels of bone-specific alkaline phosphatase (BAP), that is, elective marker of bone formation. Importantly, multiple regression analysis revealed that hydroperoxides is a determinant factor for the statistical association between lumbar spine BMD and CTX-1 levels. Taken together, our data suggest that OxS might mediate, by enhancing bone resorption, the uncoupling of bone turnover that underlies PO development.

Systemic Oxidative Stress and Conversion to Dementia of Elderly Patients with Mild Cognitive Impairment

Mild cognitive impairment (MCI) is regarded as a prodromal phase of late onset Alzheimers disease (LOAD). It has been proposed that oxidative stress (OxS) might be implicated in the pathogenesis of LOAD. The aim of this study was to investigate whether a redox imbalance measured as serum level of hydroperoxides (i.e., by-products of lipid peroxidation) and/or serum antioxidant capacity might be predictive of the clinical progression of MCI to LOAD. The levels of these two markers were measured in 111 patients with MCI (follow-up: 2.0 ± 0.6 years), 105 patients with LOAD, and 118 nondemented healthy controls. Multivariate analysis adjusted for potential confounding factors, including age, gender, smoking, and comorbidities, showed a significant increase (P < 0.05) in baseline levels of OxS in MCI and LOAD as compared to cognitive healthy controls. No differences in either of OxS markers were found by comparing MCI patients who converted (n = 29) or not converted (n = 82) to LOAD. Overall, these results suggest that systemic OxS might be a precocious feature of MCI and LOAD. However, the role of OxS as an early prognostic marker of progression to LOAD needs further investigations.

Oxidative challenge in Alzheimer's disease: state of knowledge and future needs

A large body of experimental and postmortem findings indicate that Alzheimers disease (AD) is associated with increased oxidative stress (OxS) levels in the brain. Despite the current limitations of OxS assessment in living subjects, recent data suggest that oxidative challenge might increase early both in the central nervous system and peripheral fluids. The aim of this review was to provide an overview of the existing literature linking systemic OxS to brain OxS in AD. We firmly believe that continued research aimed at overcoming the methodological and design issues affecting the body of studies in this field is mandatory for successful development of an effective antioxidant-based treatment of AD.

PON-1 and ferroxidase activities in older patients with mild cognitive impairment, late onset Alzheimer's disease or vascular dementia.

Abstract Background: A large body of evidence suggests that not only cerebral but also systemic oxidative stress (OxS) might be involved in the pathogenesis of late onset Alzheimer’s disease (LOAD) and vascular dementia (VAD), as well as of the prodromal phase of dementia, the so-called mild cognitive impairment (MCI). In the present study, we evaluated whether paraoxonase 1 (PON-1) and ferroxidase (FeOx) activities, because of their well acknowledged effectiveness as systemic antioxidants, might be associated with dementia and/or MCI. Methods: Serum arylesterase and paraoxonase of PON-1, along with FeOx I (ceruloplasmin-related) and II activities were assessed in 223 MCI, 162 LOAD, 65 VAD patients, and in 143 older normal cognitive controls. Results: Among the enzymatic activities examined, only arylesterase significantly changed across the groups (ANOVA: p<0.001), with similar lower levels in MCI, LOAD, and VAD compared to controls. By multivariate logistic regression analysis we showed that, in respect to controls, low levels (under the median value) of serum arylesterase were independently associated with an increase in the likelihood of being affected by LOAD [odds ratio (OR) 2.8, 95% confidence interval (CI) 1.5–5.0], VAD (OR 2.7, 95% CI 1.2–6.2), or MCI (OR 2.3, 95% CI 1.3–3.8). Conclusions: Overall, our results suggest that depression of PON-1, and in particular, of arylesterase activity, in serum might be an early feature of dementia-related diseases. Further longitudinal exploration of the role of this enzyme in the onset and progression of these disorders are required.

Serum paraoxonase and arylesterase activities of paraoxonase‐1 (PON‐1), mild cognitive impairment, and 2‐year conversion to dementia: A pilot study

Converging lines of evidence suggest that paraoxonase‐1 (PON‐1) may confer protection against inflammatory and oxidative challenge which, in turn, plays a key‐role in the onset and progression of dementia. The aim of this study was to evaluate whether serum PON‐1 paraoxonase/arylesterase activities might predict the clinical conversion of mild cognitive impairment (MCI) to late‐onset Alzheimers disease (LOAD) or vascular dementia (VAD). Serum paraoxonase and arylesterase activities were measured by spectrophotometric assays at baseline in 141 MCI patients (median age: 77 years; interquartile range 71–81) and in 78 healthy controls (median age: 76 years; interquartile range 73–79). After 2 years of follow‐up, 86 MCI remained stable (MCI/MCI), 34 converted to LOAD (MCI/LOAD), whereas 21 converted to VAD (MCI/VAD). Baseline arylesterase activity was lower in all MCI groups compared with controls (all p < 0.01), whereas paraoxonase activity was lower in MCI/VAD group compared to controls (p < 0.05) and MCI/MCI patients (p = 0.009). Low paraoxonase and arylesterase activities (I quartile) were associated to higher risk of conversion to VAD (OR: 3.74, 95% CI: 1.37–10.25 and OR: 3.16, 95% CI: 1.17–8.56, respectively). Our results suggest that in MCI patients low PON‐1 activity might contribute to identify individuals susceptible to develop vascular dementia.

Impaired enzymatic defensive activity, mitochondrial dysfunction and proteasome activation are involved in RTT cell oxidative damage

A strong correlation between oxidative stress (OS) and Rett syndrome (RTT), a rare neurodevelopmental disorder affecting females in the 95% of the cases, has been well documented although the source of OS and the effect of a redox imbalance in this pathology has not been yet investigated. Using freshly isolated skin fibroblasts from RTT patients and healthy subjects, we have demonstrated in RTT cells high levels of H2O2 and HNE protein adducts. These findings correlated with the constitutive activation of NADPH-oxidase (NOX) and that was prevented by a NOX inhibitor and iron chelator pre-treatment, showing its direct involvement. In parallel, we demonstrated an increase in mitochondrial oxidant production, altered mitochondrial biogenesis and impaired proteasome activity in RTT samples. Further, we found that the key cellular defensive enzymes: glutathione peroxidase, superoxide dismutase and thioredoxin reductases activities were also significantly lower in RTT. Taken all together, our findings suggest that the systemic OS levels in RTT can be a consequence of both: increased endogenous oxidants as well as altered mitochondrial biogenesis with a decreased activity of defensive enzymes that leads to posttranslational oxidant protein modification and a proteasome activity impairment.

Metabolic transitions at menopause: In post-menopausal women the increase in serum uric acid correlates with abdominal adiposity as assessed by DXA

OBJECTIVES The present study aimed to investigate any associations between parameters of body fat mass distribution and levels of serum uric acid (sUA), a well-documented cardiovascular risk factor, among non-obese women ranging from pre- to post-menopausal status. METHODS In this cross-sectional population-based study we assessed body fat distribution by dual-energy-X-ray absorptiometry (DXA), and sUA levels in 101 pre- and 134 post-menopausal non-obese apparently healthy women. RESULTS Multivariate stepwise regression analysis revealed that sUA was independently associated to the indicators of overall fatness, i.e. body mass index (β=0.339, p<0.001) and DXA-assessed total and percentage body fat (β=0.366, p<0.001 and β=0.412, p<0.001, respectively), only among post-menopausal women. Within this sample subset, trunk (i.e. central) fat mass emerged as a strong predictor of sUA (β=0.408, p<0.001), after taking the potential confounders (including body mass index) into account. CONCLUSION Central fat accumulation was found to be independently associated with higher sUA levels among non-obese women in post- but not among those in pre-menopause.

Waist circumference and dual-energy X-ray absorptiometry measures of overall and central obesity are similarly associated with systemic oxidative stress in women

Abstract Growing evidence suggests that overall and abdominal obesity might lead to oxidative stress (OxS), which, in turn, plays a key role in the pathogenesis of a wide spectrum of diseases. In this study, for the first time, we compared the correlations of indirect, i.e. anthropometric, and direct, by dual energy X-ray absorptiometry (DXA), measures of body fat with circulatory OxS markers in women. To address this issue, we assessed central and total body fat mass (FM) by DXA, and serum levels of advanced oxidation protein products (AOPP), thiols and hydroperoxides in 275 healthy women (age 21–65 years; body mass index [BMI] 21.1–32.0 kg/m2; waist circumference [WC] 60.1–109.9 cm). Among the markers considered in the study, only hydroperoxides levels, i.e. by-products of lipid peroxidation, were significantly (p < 0.05 for all) and positively correlated to body fat accumulation after controlling for confounding factors. In particular, this marker was found to be similarly associated with DXA-derived total FM, total FM % and trunk FM as well as with WC. Of note, hydroperoxides appeared to be correlated with abdominal but not with general obesity, as classified according to standard WC and BMI cut-offs, respectively. In conclusion, taken together our data demonstrated that, at least in women, the measurement of body FM by DXA has no advantage over the simpler and cheaper WC with regard to their associations with systemic OxS markers. Moreover, WC emerged as a superior potential predictor of OxS compared to the other most commonly used anthropometric measures (including BMI and waist to hip ratio).

Accumulation of central fat correlates with an adverse oxidative balance in non-obese postmenopausal women.

Abstract The aim of the present study was to investigate whether accumulation of central fat is correlated with systemic oxidative stress (OxS) in non-obese apparently healthy postmenopausal women. Serum parameters of OxS (hydroperoxides and non-enzymatic antioxidants) along with body fat distribution, as assessed by dual-energy-X-ray absorptiometry (DXA), were evaluated in 134 non-obese postmenopausal women. Multiple regression analysis showed that central (trunk) fat significantly correlated with both markers of OxS independently of confounding factors (i.e. BMI, smoking, age, hypertension, legs and arms fat mass). In specific, the standardized regression coefficient was positive for hydroperoxides (β = 0.324, p < 0.05) and negative for antioxidants (β = −0.495, p < 0.01) level. In conclusion, the current data showed that the increase in central fat is an independent predictor of OxS condition among non-obese women in postmenopausal status. The possible pro-oxidant effects of the excess in central adiposity might be more harmful among post- than among pre-menopausal women, due to the postulated ability of E2 to contrast oxidative challenge and the related diseases.