Biomedical subjects

N Santanam

Publications and source records attributed to N Santanam.

At least 19 recordsLinked to original sources

PubMed2004

A novel alkaloid antioxidant, Boldine and synthetic antioxidant, reduced form of RU486, inhibit the oxidation of LDL in-vitro and atherosclerosis in vivo in LDLR(-/-) mice.

A corollary to the oxidation hypothesis of atherosclerosis is that the consumption of antioxidants is beneficial. However, the literature is divided in support of this conclusion. In this study, Boldine, an alkaloid of Peumus boldus and reduced form of RU486, was tested for their antioxidant potency both in, in vitro oxidation system and in mouse models. Boldine decreased the ex-vivo oxidation of low-density lipoprotein (LDL). Two different in vivo studies were performed to study the effect of these compounds on the atherosclerotic lesion formation in LDLR(-/-) mice. In study I, three groups of LDLR(-/-) mice (N = 12 each) were fed an atherogenic diet. Group 1 was given vehicle and group 2 and 3 were given 1mg of Boldine or Red RU per day for 12 weeks. In study II, two groups of LDLR(-/-) mice N = 10 each) were fed an atherogenic diet. Group 1 was given vehicle and group 2 was given 5mg of Boldine per day. The results indicated that there was a decrease in lesion formation reaching a 40% reduction due to Boldine and 45% reduction by Red RU compared to controls. The in vivo tolerance of Boldine in humans (has been used as an herbal medicine in other diseases) should make it an attractive alternative to Vitamin E.

Analysis of Variance↗

PubMed2001

Cholesterol depletion inhibits epidermal growth factor receptor transactivation by angiotensin II in vascular smooth muscle cells: role of cholesterol-rich microdomains and focal adhesions in angiotensin II signaling.

Angiotensin II (Ang II) induces transactivation of the epidermal growth factor (EGF) receptor (EGF-R), which serves as a scaffold for various signaling molecules in vascular smooth muscle cells (VSMCs). Cholesterol and sphingomyelin-enriched lipid rafts are plasma membrane microdomains that concentrate various signaling molecules. Caveolae are specialized lipid rafts that are organized by the cholesterol-binding protein, caveolin, and have been shown to be associated with EGF-Rs. Angiotensin II stimulation promotes a rapid movement of AT(1) receptors to caveolae; however, their functional role in angiotensin II signaling has not been elucidated. Here we show that cholesterol depletion by beta-cyclodextrin disrupts caveolae structure and concomitantly inhibits tyrosine phosphorylation of the EGF-R and subsequent activation of protein kinase B (PKB)/Akt induced by angiotensin II. Similar inhibitory effects were obtained with other cholesterol-binding agents, filipin and nystatin. In contrast, EGF-R autophosphorylation and activation of Akt/PKB in response to EGF are not affected by cholesterol depletion. The early Ang II-induced upstream signaling events responsible for transactivation of the EGF-R, such as the intracellular Ca(2+) increase and c-Src activation, also remain intact. The EGF-R initially binds caveolin, but these two proteins rapidly dissociate following angiotensin II stimulation during the time when EGF-R transactivation is observed. The activated EGF-R is localized in focal adhesions together with tyrosine-phosphorylated caveolin. These findings suggest that 1) a scaffolding role of caveolin is essential for EGF-R transactivation by angiotensin II and 2) cholesterol-rich microdomains as well as focal adhesions are important signal-organizing compartments required for the spatial and temporal organization of angiotensin II signaling in VSMCs.

Angiotensin II↗

PubMed2001

Tacrolimus, cyclosporine and plasma lipoproteins in renal transplant recipients.

To compare the effect of tacrolimus (FK506) and cyclosporine (CsA) on plasma lipoproteins in renal transplant recipients receiving maintainance therapy, the following prospective study was undertaken. Blood from nineteen recipients on tacrolimus (FK group) and from twenty-one on CsA (CsA group) was collected at baseline, 3-, 6-, and 10-month intervals. Plasma lipids, lipoproteins and oxidation properties of lipoproteins were determined. Plasma total cholesterol, low density lipoprotein (LDL) cholesterol, and apolipoprotein B (apoB) were substantially increased in both groups, although only the CsA group showed significant differences at all time intervals and at the baseline. High density lipoprotein cholesterol, triglycerides, and apolipoprotein A varied in both groups at time intervals from the baseline, but not significantly. The susceptibility to oxidation of LDL isolated from the FK group at all times was uninfluenced by the tacrolimus treatment, and values were comparable to those obtained from LDL isolated from healthy individuals. A significantly higher susceptibility to oxidation as indicated by the shorter time required to start the formation of conjugated dienes was observed in LDL isolated from the CsA group at 3 and at 6 months of therapy. Tacrolimus-treated patients appear to have less hyperlipidemic and have LDL less susceptible to oxidation than patients treated with CsA.

Adult↗

PubMed2001

Did the antioxidant trials fail to validate the oxidation hypothesis?

Most clinical trials on antioxidants using vitamin E or beta-carotene have failed to note any significant change in cardiovascular endpoints. The results of these studies have been interpreted as a setback for the oxidation hypothesis. An analysis of the hypothesis and the trials, however, points out major misconceptions about the hypothesis and unjustified outcome expectations. Wrong selection of patient population, endpoints that are incompatible with the hypothesis, poor choice of antioxidants, and lack of inclusion of biochemical markers of oxidative stress and markers of vascular response are some of the contributors to the "failure" of these trials.

Antioxidants↗

PubMed2001

Regulation of colony stimulating factor-1 (CSF-1) in endometrial cells: glucocorticoids and oxidative stress regulate the expression of CSF-1 and its receptor c-fms in endometrial cells.

OBJECTIVE: To evaluate the regulation and expression of CSF-1 and its receptor c-fms in endometrial cells. DESIGN: In vitro study. SETTING: Research and teaching institution. PATIENT(S): None. INTERVENTION(S): In vitro experimental study. MAIN OUTCOME MEASURE(S): The effect of glucocorticoid and oxidative stress on the expression of CSF-1 and c-fms in endometrial cells. RESULT(S): Cultured nonmalignant EM42 cells not only express CSF-1 and c-fms but are also capable of responding to exogenous CSF-1. We have also seen that glucocorticoids can regulate the expression of CSF-1/c-fms in endometrial cells. Furthermore, this study shows that oxidative stress plays a significant role in the induction of CSF-1 and its receptor c-fms. CONCLUSION(S): The results suggest that CSF-1 may promote the growth of nonmalignant endometrial cells in both an autocrine and paracrine manner and that endometrial cells under oxidative stress induce CSF-1 and c-fms.

Cell Line↗

PubMed2001

Irbesartan, an angiotensin type 1 receptor inhibitor, regulates markers of inflammation in patients with premature atherosclerosis.

OBJECTIVES: This study assessed the role of angiotensin II type 1 (AT1) receptor antagonists on inflammatory mechanisms involved in atherogenesis. Specific inflammatory markers included solubilized tumor necrosis factor-alpha receptor II (sTNF-alphaRII), vascular cell adhesion molecule-1 (VCAM-1) and superoxide. In addition, the AT1 receptor blocker irbesartan was evaluated for its ability to suppress these markers in individuals with atherosclerosis. BACKGROUND: Mechanisms involved in the complex process of atherogenesis include alterations in the inflammatory responses. The use of compounds that suppress these responses may reduce the degree of damage seen in atherosclerosis. METHODS: With a cross-sectional study design, 33 normotensive patients with stable coronary artery disease (CAD) were treated with irbesartan for a 24-week period. These patients were compared against a control population with no known coronary atherosclerosis. Marker levels were measured by enzyme-linked immunosorbent assay technique and lucigenin chemiluminescence assay and statistically evaluated by two-way repeated measures analysis of variance. RESULTS: All patients with coronary artery disease had increased levels of inflammatory molecules over those of control patients. Treatment with irbesartan in these patients significantly reduced levels of inflammatory molecules measured. Soluble VCAM-1 levels were reduced by 36%; soluble TNF-alpha levels were reduced by 54% and superoxide level decreased by 52%. Maximal suppression of inflammatory markers by irbesartan therapy in patients with CAD was seen at 12 weeks. CONCLUSIONS: The effect of irbesartan on each inflammatory marker is significant. Our results show that use of irbesartan may retard the inflammatory process seen in premature forms of atherosclerosis.

Adult↗

PubMed2001

Increased myeloperoxidase and lipid peroxide-modified protein in gynecological malignancies.

Oxidative stress has been implicated in several diseases, including cancer. Oxidants induce oncogenes and their products associated with cell growth. Even though epidemiological studies implicate oxidants in promoting cancer, there is still a lack of in vivo evidence for the same. In this study, we measured the levels of myeloperoxidase (MPO), an enzyme associated with oxidation and autoantibodies to lipid peroxide-modified protein (LOOH-RSA), in the plasma of subjects with gynecological cancers. The gynecological cancer subjects (n = 201) had higher plasma MPO and LOOH-RSA levels compared with control subjects (n = 60). Immunohistochemical analysis of tissues revealed that immunostaining for MPO and LOOH-RSA was higher in cancer tissues compared with controls. The staining was specific to cell types and not ubiquitously present. Neutrophils, monocytes/macrophages, and natural killer cells have been proposed to play a role in cancer promotion and progression. This study proposes a role for oxidative stress and especially MPO in cancer.

Adolescent↗

PubMed2001

Role of arterial wall antioxidant defense in beneficial effects of exercise on atherosclerosis in mice.

The mechanism(s) by which exercise reduces atherogenic risk remains unknown. This study tested the hypothesis that sustained exercise-induced oxidative stress may increase antioxidant defense in the arterial wall. Acute exercise induced an increase in antibodies to oxidatively modified proteins and catalase in the aortic walls of normal mice compared with sedentary control mice. In male atherogenic diet-fed low density lipoprotein (LDL) receptor-deficient mice, exercise lowered plasma cholesterol (15%) and decreased atherosclerotic lesions by 40% compared with values in sedentary control mice, with a concomitant increase in arterial catalase and endothelial NO synthase. Because these mice lack the LDL receptor, the results indicate that the LDL receptor might not be responsible for the exercise-induced lowering of plasma cholesterol. Vitamin E supplementation to exercising LDL receptor-deficient mice did not reduce atherosclerotic lesion formation significantly as opposed to lesion formation in untreated exercised mice. Moreover, vitamin E counteracted the beneficial effects of exercise by preventing the induction of aortic catalase activity and endothelial NO synthase expression. These results might indicate that although vitamin E might have prevented the exercise-induced oxidative stress, its availability in the artery was insufficient to prevent the atherosclerotic process. These results indicate that exercise-induced plasma oxidative stress could be responsible for the prevention of atherosclerosis by stimulating arterial antioxidant response. Furthermore, vitamin E supplementation could be deleterious in exercisers by inhibiting antioxidant enzyme buildup in the arterial wall.

Animals↗

PubMed2000

RU486-induced growth inhibition of human endometrial cells.

OBJECTIVE: To determine the direct action of RU486 on endometrial cell proliferation and to differentiate whether the antioxidant or the antiprogesterone property of RU486 is predominately responsible for its effect on cell growth. DESIGN: In vitro study comparing the effects of RU486 (antiprogesterone and antioxidant), reduced RU486 (antioxidant), ZK112,993 (antiprogesterone), and lazaroid U74,500A (antioxidant) on endometrial cell growth. The human endometrial cell line EM42 was used in transient transfection assays to confirm the relative antiprogesterone potency of the various compounds. SETTING: Academic medical center PATIENT(S): Women presenting with pelvic pain or infertility and diagnosed with endometriosis at time of surgery or women desiring tubal ligation with a normal pelvis (controls). INTERVENTION(S): Endometrial cell cultures were treated with RU486, reduced RU486, lazaroid U74,500A, and ZK112,993. MAIN OUTCOME MEASURE(S): Tritiated thymidine incorporation was used to assess cell growth. Inhibition of progesterone induction of transiently transfected reporter plasmids was used to measure antiprogesterone activity of compounds studied. RESULT(S): RU486 reduced cell growth in a dose-dependent fashion of the endometrial cell lines EM42 and RL95-2 and of endometrial and endometriosis cells from primary culture. After being reduced, RU486 lost most of its antiprogesterone activity but retained its antiproliferative properties. ZK112,993 was similar in potency to RU486 as a progesterone antagonist but did not significantly modify endometrial cell growth. Lazaroid U74,500A was devoid of antiprogesterone activity but was shown to be a potent antiproliferative agent. CONCLUSION(S): RU486 has a direct inhibitory effect on human endometrial cell growth. This activity appears to be at least partly mediated through its antioxidant property.

Antioxidants↗

PubMed2000

Potential role of oxidized lipids and lipoproteins in antioxidant defense.

The atherogenic oxidative modification of low-density lipoprotein is suggested to occur in the aortic intima. There is reasonable evidence to suggest that antioxidants might be beneficial in preventing or retarding the progression of atherosclerosis. Exercise, estrogens, and substitution of polyunsaturated fat for saturated fat are beneficial in the prevention of atherosclerosis. Yet, paradoxically, they are capable of inducing an oxidative stress. To reconcile with this paradox, we postulate that under certain conditions an oxidative stress might be beneficial by inducing antioxidant enzymes in arterial cells. However, those with genetic deficiency in antioxidant enzymes or those who poorly respond to oxidative stress or those with overwhelming plasma oxidative stress might need additional antioxidant protection.

Animals↗

PubMed2000

Lipid peroxides induce expression of catalase in cultured vascular cells.

Various forms of oxidized low-density lipoproteins (Ox-LDL) are thought to play a major role in the development of atherosclerosis. The lipid components of Ox-LDL present a plethora of proatherogenic effects in in vitro cell culture systems, suggesting that oxidative stress could be an important risk factor for coronary artery disease. However, buried among these effects are those that could be interpreted as antiatherogenic. The present study demonstrates that various oxidants, including oxidized fatty acids and mildly oxidized forms of LDL (MO-LDL), are able to induce catalase (an antioxidant enzyme) expression in rabbit femoral arterial smooth muscle cells (RFASMC), RAW cells (macrophages), and human umbilical vein endothelial cells (HUVEC). In RFASMC, catalase protein, mRNA, and the enzyme activity are increased in response to oxidized linoleic acid (13-hydroperoxy-9,11-octadecadienoic acid [13-HPODE] and 13-hydroxy-9,11-octadecadienoic acid [13-HODE]), MO-LDL, or hydrogen peroxide (H(2)O(2)). Such an increase in catalase gene expression cannot totally be attributed to the cellular response to an intracellular generation of H(2)O(2) after the addition of 13-HPODE or 13-HODE because these agents induce a further increase of catalase as seen in catalase-transfected RFASMC. Taken together with the induction of heme oxygenase, NO synthase, manganese superoxide dismutase (Mn-SOD), and glutathione synthesis by oxidative stress, our results provide yet more evidence suggesting that a moderate oxidative stress can induce cellular antioxidant response in vascular cells, and thereby could be beneficial for preventing further oxidative stress.

Animals↗

PubMed1999

Autoantibodies to markers of oxidative stress are elevated in women with endometriosis.

OBJECTIVE: To measure autoantibodies that recognize oxidatively modified proteins in the sera of women with surgically proven endometriosis. DESIGN: Prospective study. SETTING: Tertiary care academic medical center. PATIENT(S): Women undergoing surgery for endometriosis or tubal ligation. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Serum and peritoneal fluid autoantibody titers to malondialdehyde-modified low-density lipoprotein, oxidized low-density lipoprotein, and lipid peroxide-modified rabbit serum albumin determined by ELISA. Correlation of autoantibody titers with revised American Fertility Society staging classification, symptoms, and morphologic type of endometriosis. RESULT(S): Mean (+/-SEM) serum autoantibody titers (in optical density units) to the three antigens were as follows: [1] lipid peroxide-modified rabbit serum albumin, 0.49 +/- 0.12 units in the patients with endometriosis and 0.2 +/- 0.02 units in the controls; [2] oxidized low-density lipoprotein, 0.22 +/- 0.005 units in the patients with endometriosis and 0.18 +/- 0.006 units in the controls; and [3] malondialdehyde-modified low-density lipoprotein, 0.21 +/- 0.005 units in the patients with endometriosis and 0.16 +/- 0.003 units in the controls. There was no correlation between autoantibody titers and revised American Fertility Society stage, symptoms, or morphologic type of endometriosis. Peritoneal fluid did not contain autoantibodies to any of the three antigens. CONCLUSION(S): Autoantibodies to markers of oxidative stress were significantly increased in women with endometriosis. These findings strongly support our data demonstrating that women with endometriosis have enhanced oxidative stress.

Adolescent↗

PubMed1999

Uptake of 13-hydroperoxylinoleic acid by cultured cells.

Oxidized free fatty acids have profound effects on cultured cells. However, little is known about whether these effects depend on their uptake and metabolism by cells or primarily involve their interaction with cell-surface components. We determined the uptake and metabolism of unoxidized (linoleic or oleic acid) and oxidized linoleic acid (13-hydroperoxyoctadecadienoic acid, 13-HPODE) by endothelial cells, smooth muscle cells, and macrophages. We show that 13-HPODE is poorly taken up by cells. The levels of uptake were dependent on the cell type but were independent of the expression of CD36. 13-HPODE was also poorly used by microsomal lysophosphatidylcholine acyltransferase that is involved in the formation of phosphatidylcholine. Based on these results, we suggest that most of the biological effects of 13-HPODE and other oxidized free fatty acids on cells might involve a direct interaction with cell-surface components. Alternatively, very small amounts of oxidized free fatty acids that enter the cell may have effects, analogous to those of hormones or prostanoids.

Animals↗

PubMed1999

Overexpression of human catalase gene decreases oxidized lipid-induced cytotoxicity in vascular smooth muscle cells.

Reactive oxygen metabolites such as hydrogen peroxide (H(2)O(2)) and oxidized fatty acids are proinflammatory and are involved in the pathophysiology of various diseases including atherosclerosis. The effects of these oxidants could be inhibited by the external addition of an antioxidant, suggesting the promotion or propagation of further oxidation. In this study, we describe the stable overexpression of human catalase in smooth muscle cells and the resistance of these cells to cytotoxicity induced not only by the addition of H(2)O(2) but also by the addition of 13-hydroperoxyoctadecadienoic acid (13-HPODE). The results pose an intriguing possibility of the generation of H(2)O(2) from a peroxidized fatty acid. Accordingly, incubation of cells with both 13-HPODE and 13-hydroxyoctadecadienoic acid resulted in the generation of intracellular H(2)O(2). To explain the observed results by which catalase could overcome the effects of 13-HPODE, we propose that oxidized fatty acids are degraded in the cellular peroxisomes, resulting in the generation of H(2)O(2). In other words, the cellular effects of peroxidized fatty acids could be attributed to the generation of H(2)O(2).

Animals↗

PubMed1999

Oxidants and antioxidants in atherogenesis. An appraisal.

Oxidized low density lipoprotein (Ox-LDL) has a plethora of components that are not present in native LDL. Their presence and quantity depends on the nature, type, and extent of oxidation. Lipids esterified to oxidized fatty acids are the major components formed during the early phase of oxidation and these show a number of proatherogenic properties in in vitro cell culture systems. Recently, evidence has been forthcoming to suggest that some of these oxidized lipids also could elicit "antioxidant;-antiatherogenic" responses from cells. Moreover, some of the cellular effects of Ox-LDL that were previously interpreted as atherogenic could also be reinterpreted to suggest an antiatherogenic cellular response. In addition to the above, the antioxidants that are carried in lipoproteins could have anomalous behavior attributable to their metabolism, ability to be internalized by arterial cells, and the presence of oxidative systems that could render them prooxidants. In conclusion, there are numerous contributing factors that need to be studied and understood before antioxidant therapy becomes an option for the treatment for cardiovascular diseases.

Animals↗

PubMed1998

Oxidized low-density lipoprotein, a two-faced Janus in coronary artery disease?

The word antioxidant has become a household term, and every day we are bombarded with claims of antioxidant protection against a host of diseases. Atherosclerosis, cancer, gastric ulcers, memory loss, rheumatoid arthritis, endometriosis, pregnancy complications, hypertension, stroke, and a host of other diseases have been suggested to be induced by oxidative stress, and antioxidants have been suggested to be beneficial in the prevention and treatment of these disorders. While some of these may be exuberant claims, atherosclerosis is one disease in which the oxidation hypothesis has taken firm roots. The oxidation of low-density lipoprotein (LDL) has been suggested to be a key step in the initiation of the early atherosclerotic lesion. A number of proatherogenic effects have been described for both the protein and lipid components of oxidized low-density lipoprotein. In this commentary, a brief description of the involvement of oxidation and the potential for antioxidant treatment for cardiovascular disease will be provided. However, there are innumerable questions plaguing the hypothesis; this commentary, therefore, will also serve as a devil's advocate and propose that some form of oxidation might actually be beneficial.

Animals↗

PubMed1998

Does acute exercise affect the susceptibility of low density lipoprotein to oxidation?

This study describes the effect of an acute exercise bout on the susceptibility of isolated low density lipoprotein (LDL) to in vitro oxidation. LDL was isolated from 23 subjects (exercisers, n = 11; sedentary, n = 12) immediately before and after a single bout of exercise (30 min of treadmill work at 55% & 70% peak oxygen consumption (VO2 peak) for exercisers and sedentary, respectively). A statistically significant decrease in lag time for LDL oxidation was observed following exercise compared to baseline (96.1+/-23.5 min vs. 92.1+/-23.3 minutes; n = 23, p < or = .03) using a 5 microM copper system. There was a statistically significant increase in plasma myeloperoxidase (MPO) levels following exercise compared to baseline values ( 1.58+/-.91 ng/dl versus 2.08+/-1.2 ng/dl; n = 12, p < or = .03). These results suggest that the 30 min exercise bout at a moderate intensity and duration was a sufficient oxidative stress to increase the susceptibility of LDL to in vitro oxidation. Additionally, the exercise bout appeared to activate neutrophils, subsequently releasing MPO protein.

Adult↗

PubMed1998

Regulation of monocyte to macrophage differentiation by antiglucocorticoids and antioxidants.

OBJECTIVE: Our purpose was to examine RU 486 and related compounds on monocyte to macrophage differentiation through scavenger receptors and cellular adhesion. STUDY DESIGN: Human monocytes were isolated, cultured, and treated with dexamethasone, levonorgestrel, RU 486, and other structurally related compounds alone or in combination. Macrophage scavenger receptor activity, inhibited by glucocorticoids and associated in the current literature with macrophage cellular adhesion, was determined in this study by counting the number of adherent cells after treatment. In addition, fluorescent-labeled acetyl-low-density lipoprotein uptake was determined as a function of scavenger receptor biologic activity. RESULTS: Dexamethasone, levonorgestrel (antiglucocorticoid only) and RU 486 (antiglucocorticoid and antioxidant) all significantly decreased adherent macrophages (4%, 52%, and 74% of control). Levonorgestrel, however, demonstrated a marked uptake of fluorescent-labeled scavenger receptor ligand. RU 486 and dexamethasone were antagonistic when combined (P < .001); levonorgestrel was less antagonistic but, however, still significant (P < .05). Reduced RU 486 (antioxidant but loses antiglucocortioid activity) decreased cellular adhesion, yet scavenger receptor function was enhanced. Both probucol (extracellular mechanism of action) and probucol analog (intracellular action) markedly up-regulated scavenger function, but once again a separation of adhesion from scavenger activity was noted. Vitamin E (antioxidant) and onapristone (antioxidant and antiglucocorticoid) had virtually little to no effect on adhesion and scavenger receptor activity. Finally, pyrrolidine dithiocarbamate, a potent oxygen-free radical quencher, was toxic to all cells examined. CONCLUSIONS: RU 486 is a known antiglucocorticoid with novel antioxidant properties first demonstrated by our laboratories. Levonorgestrel has antiglucocorticoid but no antioxidant activity. RU 486 antagonized the inhibitory effect of dexamethasone on scavenger receptor development, whereas levonorgestrel was stimulatory. A separation of scavenger receptor-induced cellular adhesion and scavenger receptor internalized ligand was demonstrated by (1) reduced RU 486, which loses its antiglucocorticoid activity but retains its antioxidant activity, and (2) probucol analog, which is chemically altered to allow intracellular entry. Glucocorticoids decrease the development of scavenger receptors, whereas antioxidants regulate inflammatory cytokines by intracellular mechanisms. It is therapeutically important to up-regulate scavenger receptor activity by antiglucocorticoids in the peritoneal cavity of women with endometriosis. However, because these mechanisms also induce inflammatory cytokines, a balance of antioxidants and antiglucocorticoids such as those demonstrated in the above study may prove beneficial.

Antioxidants↗