Impact of 30-Day Oral Dosing with N-acetyl-l-cysteine on Sprague-Dawley Rat Physiology

N-acetyl cysteine augments adipose tissue-derived stem cell efficacy on inflammatory markers and regulatory T cell system balance in an allergic asthma model

BACKGROUND

Allergic asthma is a destructive inflammatory process in the respiratory system. The anti-inflammatory and antioxidant effects of N-acetylcysteine (NAC) have been reported in patients with obstructive pulmonary disease. On the other hand, several studies have shown the modulatory effects of mesenchymal stem cells on the immune system and inflammatory responses. Accordingly, the purpose of the current study was to evaluate the effect of administration of adipose tissue-derived stem cells (ADSCs) plus NAC on regulatory T cell system balance in an allergic asthma model.

METHODS

Eighty Sprague- Dawley rats were randomly divided into the following groups: Control, Plasmalite, Allergic asthma, Allergic asthma + ADSCs, NAC, Allergic asthma + NAC, Allergic asthma + ADSCs + NAC and Allergic asthma + Prednisolone. at the end of the experiment, arterial blood gas analysis, inflammatory cell counts in bronchoalveolar lavage fluid (BALF), inflammatory cytokine concentration, total IgE and specific OVA-IgE levels, gene expression levels of CD4+-T cell subsets, pulmonary indicators, edema, and lung histopathology were evaluated in all groups.

RESULTS

Administration of NAC plus ADSCs demonstrated a significant decrease in total WBC and eosinophil counts, which was in line with remarkable decrease in IL-17 and TNF-α concentrations and increases in IL-10 level compared with other treated groups. NAC plus ADSC treatment showed significant increases in Treg gene expression, although Th17 and Th2 expression significantly decreased compared with that in prednisolone- treated rats.

CONCLUSION

The results of the present study documented that the administration of ADSCs plus NAC has an inhibitory effect on the inflammation caused by allergic asthma in a rat model. The improvement of inflammatory indexes was significantly higher than that with prednisolone treatment.

N-Acetylcysteine Supplementation Improves Testicular Haemodynamics, Testosterone Levels, Seminal Antioxidant Capacity and Semen Quality in Heat-Stressed Goat Bucks

Heat stress (HS) disrupts testicular homeostasis because of oxidative stress. N-acetylcysteine (NAC) is a thiol compound with antioxidants, anti-inflammatory and anti-apoptotic properties. As a sequel, this research aimed to assess the ameliorative effects of NAC supplementation on the reproductive performance of goat bucks kept under environmental HS. Primarily, Doppler examination as well as semen collection and evaluation were conducted on 12 mature bucks for 2 weeks (W) as pre-heat stress control (W1 and W2) during winter (February 2023). The temperature-humidity index (THI) was 63.4-64.3 (winter season). Then during summer HS conditions (from the beginning of July till the end of August 2023) bucks were assessed before NAC supplementation (W0), afterwards they were arbitrarily assigned into two groups. The control group (CON; n = 6) received the basal diet while the NAC group (n = 6) received the basal diet in addition to oral NAC daily for 7 weeks (W1-W7). The THI was 78.1-81.6 (summer season). Testicular blood flow parameters, serum concentration of nitric oxide (NO) and testosterone were measured. Additionally, total antioxidant capacity (TAC) and malondialdehyde (MDA) content in seminal plasma and semen quality parameters were evaluated. There were marked reductions (p < 0.05) in the resistive index (RI; W1, W4 and W5), pulsatility index (PI; W2 and W4-W7), and systolic/diastolic ratio (S/D; W4-W7) in the NAC group compared to the CON group. Furthermore, testosterone and NO levels were higher (p < 0.01 and p < 0.05, respectively) in the NAC group (W2, W3, W5 and W3-W5, respectively). Seminal plasma TAC increased (p < 0.05) and MDA decreased (p < 0.05) in the NAC group (W2, W4 and W5) compared to the CON group. Moreover, there were marked improvements (p < 0.05) in semen quality parameters (mass motility, total motility, viability and normal morphology) in the NAC group. In conclusion, oral NAC supplementation could be used to enhance the reproductive performance of goat bucks during HS conditions which is supported by remarkable enhancement in testicular haemodynamics, NO, testosterone levels and semen quality parameters.

Effect of N-acetyl-L-cysteine on Testicular Tissue in Busulfan-Induced Dysfunction in the Male Reproductive System

PURPOSE

This study aimed to evaluate the protective effect of N-acetyl-L-cysteine (NAC) as an antioxidant on busulfan-induced testicular dysfunction in mice and elucidate its possible mechanism of action.

MATERIALS AND METHODS

Thirty-two C57BL/6 male mice were randomly divided into four groups (n=8/group) as follows: (1) control group (oral administration of saline [0.1 mL daily] for 35 days); (2) NAC group (oral administration of NAC [10 mg/kg daily] for 35 days); (3) busulfan group (double intraperitoneal injections of 20 mg/kg; total dose of 40 mg/kg); and (4) busulfan+NAC group (after double intraperitoneal injections of 20 mg/kg; total dose of 40 mg/kg, NAC administration [10 mg/kg daily] for 35 days). The testes were removed, weighed, and subjected to sperm parameter analysis and morphology assessment. Reproductive hormone, serum/testicular reactive oxygen species (ROS) level, oxidative stress and antioxidant markers were evaluated. The testicular expression of Nrf2 and HO-1 was examined using RT-qPCR.

RESULTS

Busulfan treatment significantly decreased testicular weight, sperm count, and serum testosterone levels. Atrophy and degeneration of germinal epithelium were observed in the busulfan group. NAC administration after busulfan treatment partially attenuated the deterioration of testis weight, sperm quality, serum hormones, histomorphometric changes, and oxidative and antioxidative status. NAC treatment resulted in a considerable improvement in Nrf2 and HO-1 mRNA expression levels.

CONCLUSIONS

This study provides compelling evidence that NAC as a potent antioxidant has significant protective effects against busulfan-induced male reproductive impairment possibly through modification of the Nrf2/HO-1 signaling pathway.

Therapeutic role of N-acetyl cysteine (NAC) for the treatment and/or management of SARS-CoV-2-induced lung damage in hamster model

Oxidative stress by reactive oxygen species (ROS) has been hypothesized to be the major mediator of SARS-CoV-2-induced pathogenesis. During infection, the redox homeostasis of cells is altered as a consequence of virus-induced cellular stress and inflammation. In such scenario, high levels of ROS bring about the production of pro-inflammatory molecules like IL-6, IL-1β, etc. that are believed to be the mediators of severe COVID-19 pathology. Based on the known antioxidant, anti-inflammatory, mucolytic and antiviral properties of NAC, it has been hypothesized that NAC will have beneficial effects in COVID-19 patients. In the current study efforts have been made to evaluate the protective effect of NAC in combination with remdesivir against SARS-CoV-2 induced lung damage in the hamster model. The SARS-CoV-2 infected animals were administered with high (500 mg/kg/day) and low (150 mg/kg/day) doses of NAC intraperitoneally with and without remdesivir. Lung viral load, pathology score and expression of inflammatory molecules were checked by using standard techniques. The findings of this study show that high doses of NAC alone can significantly suppress the SARS-CoV-2 mediated severe lung damage (2 fold), but on the contrary, it fails to restrict viral load. Moreover, high doses of NAC with and without remdesivir significantly suppressed the expression of pro-inflammatory genes including IL-6 (4.16 fold), IL-1β (1.96 fold), and TNF-α (5.55 fold) in lung tissues. Together, results of this study may guide future preclinical and clinical attempts to evaluate the efficacy of different doses and routes of NAC administration with or without other drugs against SARS-CoV-2 infection.

N-Acetylcysteine Regenerates In Vivo Mercaptoalbumin

Human serum albumin (HSA) represents the most abundant plasma protein, with relevant antioxidant activity due to the presence of the sulfhydryl group on cysteine at position 34 (Cys34), the latter being one of the major target sites for redox-dependent modifications leading to the formation of mixed disulfide linkages with low molecular weight thiols. Thiolated forms of HSA (Thio-HSA) may be useful as markers of an unbalanced redox state and as a potential therapeutic target. Indeed, we have previously reported that albumin Cys34 can be regenerated in vitro by N-Acetylcysteine (NAC) through a thiol-disulfide breaking mechanism, with a full recovery of the HSA antioxidant and antiplatelet activities. With this case study, we aimed to assess the ability of NAC to regenerate native mercaptoalbumin (HSA-SH) and the plasma antioxidant capacity in subjects with redox unbalance, after oral and intravenous administration. A placebo-controlled crossover study, single-blinded, was performed on six hypertensive subjects, randomized into two groups, on a one-to-one basis with NAC (600 mg/die) or a placebo, orally and intravenously administered. Albumin isoforms, HSA-SH, Thio-HSA, and glutathione levels were evaluated by means of mass spectrometry. The plasma antioxidant activity was assessed by a fluorimetric assay. NAC, orally administered, significantly decreased the Thio-HSA levels in comparison with the pre-treatment conditions (T0), reaching the maximal effect after 60 min (−24.7 ± 8%). The Thio-HSA reduction was accompanied by a concomitant increase in the native HSA-SH levels (+6.4 ± 2%). After intravenous administration of NAC, a significant decrease of the Thio-HSA with respect to the pre-treatment conditions (T0) was observed, with a maximal effect after 30 min (−68.9 ± 10.6%) and remaining significant even after 6 h. Conversely, no effect on the albumin isoforms was detected with either the orally or the intravenously administered placebo treatments. Furthermore, the total antioxidant activity of the plasma significantly increased after NAC infusion with respect to the placebo (p = 0.0089). Interestingly, we did not observe any difference in terms of total glutathione corrected for hemoglobin, ruling out any effect of NAC on the intracellular glutathione and supporting its role as a disulfide-breaking agent. This case study confirms the in vitro experiments and demonstrates for the first time that NAC is able to regenerate mercaptoalbumin in vivo, allowing us to hypothesize that the recovery of Cys34 content can modulate in vivo oxidative stress and, hopefully, have an effect in oxidative-based diseases.

l-Thyroxine induces left ventricular remodeling and fibrosis in rats by upregulating miR-21 in a reactive oxygen-dependent mechanism: a protective role of N-acetylcysteine

miR-21 is the most studied pro-fibrotic marker in the majority of mammalian tissues. The precise mechanism by which hyperthyroidism induces left ventricular LV fibrosis and remodeling remains unclear. In this study, we have investigated the role of miR-21 on l-thyroxine (l-Thy)-induced cardiac fibrosis in rats. Adult male Sprague-Dawley rats were divided into four groups as control, l-Thy, l-Thy + miR antagomir (inhibitor), and l-Thy + N-acetylcysteine (NAC/glutathione (GSH) precursor). Administration of l-Thy significantly increased mRNA levels of miR-21 in the LVs of the treated rats. Also, it impaired the LV systolic and diastolic function and increased the production of reactive oxygen species (ROS), the transactivation of NF-κB p65, the expression of NRLP3 inflammasome, and levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in these LVs. Concomitantly, l-Thy increased the ventricular collagen deposition, and stimulated the expression of collagen 1/3, alpha-smooth actin (α-SMA), transforming growth factor-β1, and Smad3/p-Smad3 but suppressed the expression of Smad7. All these effects were reversed by pre-treatment with miR-21 antagomir or co-administration of NAC. In conclusion, l-Thy-induced LV remodeling and fibrosis include a ROS-dependent upregulation of miR-21 which in turns activates NF-κB/NRLP3 inflammasome and suppresses SMad7.

High-dose vitamin C enhances cancer immunotherapy

Vitamin C (VitC) is known to directly impair cancer cell growth in preclinical models, but there is little clinical evidence on its antitumoral efficacy. In addition, whether and how VitC modulates anticancer immune responses is mostly unknown. Here, we show that a fully competent immune system is required to maximize the antiproliferative effect of VitC in breast, colorectal, melanoma, and pancreatic murine tumors. High-dose VitC modulates infiltration of the tumor microenvironment by cells of the immune system and delays cancer growth in a T cell-dependent manner. VitC not only enhances the cytotoxic activity of adoptively transferred CD8 T cells but also cooperates with immune checkpoint therapy (ICT) in several cancer types. Combination of VitC and ICT can be curative in models of mismatch repair-deficient tumors with high mutational burden. This work provides a rationale for clinical trials combining ICT with high doses of VitC.

N-Acetyl Cysteine Overdose Inducing Hepatic Steatosis and Systemic Inflammation in Both Propacetamol-Induced Hepatotoxic and Normal Mice

Acetaminophen (APAP) overdose induces acute liver damage and even death. The standard therapeutic dose of N-acetyl cysteine (NAC) cannot be applied to every patient, especially those with high-dose APAP poisoning. There is insufficient evidence to prove that increasing NAC dose can treat patients who failed in standard treatment. This study explores the toxicity of NAC overdose in both APAP poisoning and normal mice. Two inbred mouse strains with different sensitivities to propacetamol-induced hepatotoxicity (PIH) were treated with different NAC doses. NAC therapy decreased PIH by reducing lipid oxidation, protein nitration and inflammation, and increasing glutathione (GSH) levels and antioxidative enzyme activities. However, the therapeutic effects of NAC on PIH were dose-dependent from 125 (N125) to 275 mg/kg (N275). Elevated doses of NAC (400 and 800 mg/kg, N400 and N800) caused additional deaths in both propacetamol-treated and normal mice. N800 treatments significantly decreased hepatic GSH levels and induced inflammatory cytokines and hepatic microvesicular steatosis in both propacetamol-treated and normal mice. Furthermore, both N275 and N400 treatments decreased serum triglyceride (TG) and induced hepatic TG, whereas N800 treatment significantly increased interleukin-6, hepatic TG, and total cholesterol levels. In conclusion, NAC overdose induces hepatic and systemic inflammations and interferes with fatty acid metabolism.

An insight on safety, efficacy, and molecular docking study reports of N-acetylcysteine and its compound formulations

N-acetylcysteine (NAC) is considered as the body's major antioxidant molecules with diverse biological properties. In this review, the pharmacokinetics, safety and efficacy report on both the preclinical and clinical summary of NAC is discussed. Both in vitro and in vivo preclinical studies along with the clinical data have shown that NAC has enormous biological properties. NAC is used in the treatment of acetaminophen poisoning, diabetic nephropathy, Alzheimer's disease, schizophrenia, and ulcerative colitis, etc. Numerous analytical techniques, for instance, UPLC, LC-MS, HPLC, RP-IPC are primarily employed for the estimation of NAC in different single and fixed-dose combinations. The molecular docking studies on NAC demonstrate the binding within Sudlow's site-I hydrogen bonds and formation of NAC and BSA complexes. Various hydrophobic and hydrophilic amino acids generally exist in making contact with NAC as NAC-BSA complexes. Docking studies of NAC with the active site of the urease exposed an O-coordinated bond through nickel 3002 and a hydrogen bond through His-138. NAC and its analogs also made the allosteric pockets that helped to describe almost all favorable pose for the chaperone in a complex through the protein. Thus, we intended to highlight the several health benefits of this antioxidant compound and applications in pharmaceutical product development.

N-Acetylcysteine as an antioxidant and disulphide breaking agent: the reasons why

The main molecular mechanisms explaining the well-established antioxidant and reducing activity of N-acetylcysteine (NAC), the N-acetyl derivative of the natural amino acid l-cysteine, are summarised and critically reviewed. The antioxidant effect is due to the ability of NAC to act as a reduced glutathione (GSH) precursor; GSH is a well-known direct antioxidant and a substrate of several antioxidant enzymes. Moreover, in some conditions where a significant depletion of endogenous Cys and GSH occurs, NAC can act as a direct antioxidant for some oxidant species such as NO₂ and HOX. The antioxidant activity of NAC could also be due to its effect in breaking thiolated proteins, thus releasing free thiols as well as reduced proteins, which in some cases, such as for mercaptoalbumin, have important direct antioxidant activity. As well as being involved in the antioxidant mechanism, the disulphide breaking activity of NAC also explains its mucolytic activity which is due to its effect in reducing heavily cross-linked mucus glycoproteins. Chemical features explaining the efficient disulphide breaking activity of NAC are also explained.

The oxidative stress induced in vivo by Shiga toxin-2 contributes to the pathogenicity of haemolytic uraemic syndrome

Typical haemolytic uraemic syndrome (HUS) is caused by Shiga toxin (Stx)-producing Escherichia coli infections and is characterized by thrombotic microangiopathy that leads to haemolytic anaemia, thrombocytopenia and acute renal failure. Renal or neurological sequelae are consequences of irreversible tissue damage during the acute phase. Stx toxicity and the acute inflammatory response raised by the host determine the development of HUS. At present there is no specific therapy to control Stx damage. The pathogenic role of reactive oxygen species (ROS) on endothelial injury has been largely documented. In this study, we investigated the in-vivo effects of Stx on the oxidative balance and its contribution to the development of HUS in mice. In addition, we analysed the effect of anti-oxidant agents as therapeutic tools to counteract Stx toxicity. We demonstrated that Stx induced an oxidative imbalance, evidenced by renal glutathione depletion and increased lipid membrane peroxidation. The increased ROS production by neutrophils may be one of the major sources of oxidative stress during Stx intoxication. All these parameters were ameliorated by anti-oxidants reducing platelet activation, renal damage and increasing survival. To conclude, Stx generates a pro-oxidative state that contributes to kidney failure, and exogenous anti-oxidants could be beneficial to counteract this pathogenic pathway.

Atrial fibrillation post cardiac surgery trends toward management

Post operative atrial fibrillation (POAF) is more common than before due to increased numbers of cardiac surgeries. This in turn is associated with increased incidence of post operative complication, length of hospital stay and subsequent increase the cost of hospitalization. Therefore preventing and/or minimizing atrial fibrillation by pharmacological or nonpharmacological means is a reasonable goal. POAF has also been associated with postoperative delirium and neurocognitive decline. The precise pathophysiology of POAF is unknown, however most of the evidence suggests it is multifactorial. Different risk factors have been reported, and many studies have evaluated the prophylactic effects of different interventions. This review article highlights the incidence, risk factors, and pathogenesis, prevention, and treatment strategies of POAF.

Low-Dose D-Methionine and N-Acetyl-L-Cysteine for Protection from Permanent Noise-Induced Hearing Loss in Chinchillas

Objective. Despite efforts at public health awareness and stringent industrial standards for hearing protection, noise-induced hearing loss (NIHL) remains a formidable public health concern. Although many antioxidants have proven to be beneficial in the laboratory for prevention of permanent NIHL, low-dose combinations of compounds with different biochemical mechanisms of action may allow long-term administration with fewer side effects and equal efficacy. The mixture of D-methionine and N-acetyl-L-cysteine administered at levels less than 10% of standard dosing has not been previously reported.

Study Design. Twenty-six female adult Chinchilla laniger were placed in 4 study groups, consisting of (1) a group receiving combination 12.5 mg/kg each D-methionine and N-acetyl-L-cysteine (DMET/NAC group), (2) a group receiving 12.5 mg/kg D-methionine (DMET-only group), (3) a group receiving 12.5 mg/kg N-acetyl-L-cysteine (NAC-only group), and (4) saline controls.

Setting. Laboratory.

Subjects and Methods. All groups received twice-daily intraperitoneal injections 2 days prior to noise exposure, 1 hour before and after exposure on day 3, and for 2 days subsequently, totaling 10 doses of 125 mg/kg for each antioxidant over 5 days.

Results. Although NAC-only animals paralleled saline control recovery during 3 weeks, the DMET-only group revealed gradual improvement with statistically significant recovery in the middle frequencies. The DMET/NAC group showed significant improvement at most frequencies compared with controls ( P < .001 and P < .05).

Conclusion. Significant recovery of hearing was observed following continuous noise exposure with either DMET only or a combination of low-dose DMET/NAC, demonstrating a considerably lower dose of antioxidants required than previously reported for hearing recovery following acoustic trauma.

N-acetylcysteine inhibits chromium hypersensitivity in coadjuvant chromium-sensitized albino guinea pigs by suppressing the effects of reactive oxygen species

BACKGROUND

Chromium hypersensitivity is an important issue in occupational skin disease. When hexavalent chromium enters the cell, it can be reduced to trivalent chromium, resulting in the formation of reactive oxygen species (ROS). ROS are considered to play an important role in the progression of allergic contact dermatitis. N-acetylcysteine (NAC) could increase glutathione levels in the skin and act as an antioxidant.

AIMS

We attempted to demonstrate that NAC could inhibit chromium hypersensitivity in a coadjuvant chromium-sensitized albino guinea pig model by counteracting the formation of ROS.

METHODS

We utilized a coadjuvant chromium-sensitized albino guinea pig model to evaluate both the severity of the skin reaction by intradermal and epicutaneous elicitation tests and the sensitization rate of chromium hypersensitivity in NAC-treated and NAC-untreated albino guinea pigs (GP). Furthermore, three ROS parameters, including H(2)O(2,) malondialdehyde (MDA) levels in the skin and the oxygen radical absorbance capacity (ORAC) in plasma, were analyzed in NAC-treated and NAC-untreated coadjuvant chromium-sensitized albino GP.

RESULTS

The severity of the skin reaction in the intradermal and epicutaneous elicitation test significantly diminished when the albino GP were treated with a dose of 1200 mg/kg/day of NAC. This dose also significantly decreased the sensitization rate of chromium hypersensitivity. In addition, treatment with 1200 mg/kg/day of NAC significantly reduced the H(2)O(2) and MDA levels in the skin and significantly increased the ORAC in the plasma of albino GP. Therefore, NAC could be a potential chemopreventative agent to prevent the progression of chromium hypersensitivity.

Development of a physiologically based pharmacokinetic (PBPK) model for methyl iodide in rats, rabbits, and humans

Methyl iodide (MeI) has been proposed as an alternative to methyl bromide as a pre-plant soil fumigant that does not deplete stratospheric ozone. In inhalation toxicity studies performed in animals as part of the registration process, three effects have been identified that warrant consideration in developing toxicity reference values for human risk assessment: nasal lesions (rat), acute neurotoxicity (rat), and fetal loss (rabbit). Uncertainties in the risk assessment can be reduced by using an internal measure of target tissue dose that is linked to the likely mode of action (MOA) for the toxicity of MeI, rather than the external exposure concentration. Physiologically based pharmacokinetic (PBPK) models have been developed for MeI and used to reduce uncertainties in the risk assessment extrapolations (e.g. interspecies, high to low dose, exposure scenario). PBPK model-derived human equivalent concentrations comparable to the animal study NOAELs (no observed adverse effect levels) for the endpoints of interest were developed for a 1-day, 24-hr exposure of bystanders or 8 hr/day exposure of workers. Variability analyses of the PBPK models support application of uncertainty factors (UF) of approximately 2 for intrahuman pharmacokinetic variability for the nasal effects and acute neurotoxicity.

Distribution of Radio-LabeledN-Acetyl-L-Cysteine in Sprague-Dawley Rats and Its Effect on Glutathione Metabolism Following Single and Repeat Dosing by Oral Gavage

The distribution of radio-labeled N-Acetyl-L-Cysteine (NAC) and its impact on glutathione (GSH) metabolism was studied in Sprague-Dawley rats following single and multiple dosing with NAC by oral gavage. Radioactivity associated with administration of (14)C-NAC distributed to most tissues examined within 1 hour of administration with peak radioactivity levels occurring within 1 hour to 4 hours and for a majority of the tissues examined, radioactivity remained elevated for up to 12 hours or more. Administration of a second dose of 1,200 mg/kg NAC + (14)C-NAC 4 hours after the first increased liver, kidney, skin, thymus, spleen, eye, and serum radioactivity significantly beyond levels achieved following 1 dose. Administration of a third dose of 1,200 mg/kg NAC + (14)C-NAC 4 hours after the second dose did not significantly increase tissue radioactivity further except in the skin. GSH concentrations were increased 20% in the skin and 50% in the liver after one dose of 1,200 mg/kg NAC whereas lung and kidney GSH were unaffected. Administration of a second and third dose of 1,200 mg/kg NAC at 4 hours and 8 hours after the first did not increase tissue GSH concentrations above background with the exception that skin GSH levels were elevated to levels similar to those obtained after a single dose of NAC. Glutathione-S-transferase (GST) activity was increased 150% in the kidney and 10% in the liver, decreased 60% in the skin, and had no effect on lung GST activity following a single dose of 1,200 mg/kg NAC. Administration of a second dose of 1,200 mg/kg NAC 4 hours after the first decreased skin GST activity a further 20% whereas kidney GST activity remained elevated at levels similar to those obtained after 1 dose of NAC. Administration of a third dose of NAC 4 hours after the second dose increased liver GST activity significantly as compared to background but did not affect skin, kidney, or lung GST activity. Transient decreases in glutathione reductase (GR) activity were measured in the skin and kidney in association with repeat administration of 1,200 mg/kg NAC. Glutathione peroxidase (GxP) activity was increased in the skin, kidney, and liver suggesting that oxidative stress was occurring in these tissues in response to repeat dosing with NAC. Overall, the results of this study present the possibility that NAC could provide some benefit in preventing or reducing toxicity related to exposure to chemical irritants (particularly sulfur mustard) in some tissues by increasing tissue NAC and/or cysteine levels, GSH concentrations, and GST activity. However, follow-on studies in animals are needed to confirm that oral administration of single and multiple doses of NAC can significantly reduce skin, eye, and lung toxicity associated with sulfur mustard exposure. The finding that GxP activity is elevated, albeit transiently, following repeat administration of NAC suggests that repeat administration of NAC may induce oxidative stress in some tissues and further studies are needed to confirm this finding.

Renal antioxidant enzymes and glutathione redox status in leptin-induced hypertension

Previously, we have demonstrated that leptin increases blood pressure (BP) in the rats through two oxidative stress-dependent mechanisms: stimulation of extracellular signal-regulated kinases (ERK) by H(2)O(2) and scavenging of nitric oxide (NO) by superoxide (O(2-.)). Herein, we examined if renal glutathione system and antioxidant enzymes determine the mechanism of prohypertensive effect of leptin. Leptin administered at 0.5 mg/kg/day for 4 or 8 days increased BP and renal Na(+),K(+)-ATPase activity and reduced fractional sodium excretion; these effects were prevented by NADPH oxidase inhibitor, apocynin. Superoxide scavenger, tempol, abolished the effect of leptin on BP and renal Na(+) pump in rats receiving leptin for 8 days, whereas ERK inhibitor, PD98059, was effective in animals treated with leptin for 4 days. Leptin administered for 4 days decreased glutathione (GSH) and increased glutathione disulfide (GSSG) in the kidney. In animals receiving leptin for 8 days GSH returned to normal level, which was accompanied by up-regulation of gamma-glutamylcysteine synthetase (gamma-GCS), a rate-limiting enzyme of the GSH biosynthetic pathway. In addition, superoxide dismutase (SOD) activity was decreased, whereas glutathione peroxidase (GPx) was increased in rats receiving leptin for 8 days. Cotreatment with gamma-GCS inhibitor, buthionine sulfoximine (BSO), accelerated, whereas GSH precursor, N-acetylcysteine (NAC), attenuated leptin-induced changes in gamma-GCS, SOD, and GPx. In addition, coadministration of BSO changed the mechanism of BP elevation from H(2)O(2)-ERK to (O(2-.))-NO dependent in animals receiving leptin for 4 days, whereas NAC had the opposite effect in rats treated with leptin for 8 days. These results suggest that initial change in GSH redox status induces decrease in SOD/GPx ratio, which results in greater amount of (O)2-.)) versus H(2)O(2) in later phase of leptin treatment, thus shifting the mechanism of BP elevation from H(2)O(2)-ERK to (O(2-.))-NO dependent.

Drug-metabolizing enzymes in the skin of man, rat, and pig

The mammalian skin has long been considered to be poor in drug metabolism. However, many reports clearly show that most drug metabolizing enzymes also occur in the mammalian skin albeit at relatively low specific activities. This review summarizes the current state of knowledge on drug metabolizing enzymes in the skin of human, rat, and pig, the latter, because it is often taken as a model for human skin on grounds of anatomical similarities. However only little is known about drug metabolizing enzymes in pig skin. Interestingly, some cytochromes P450 (CYP) have been observed in the rat skin which are not expressed in the rat liver, such as CYP 2B12 and CYP2D4. As far as investigated most drug metabolizing enzymes occur in the suprabasal (i.e. differentiating) layers of the epidermis, but the rat CYP1A1 rather in the basal layer and human UDP-glucuronosyltransferase rather in the stratum corneum. The pattern of drug metabolizing enzymes and their localization will impact not only the beneficial as well as detrimental properties of drugs for the skin but also dictate whether a drug reaches the blood flow unchanged or as activated or inactivated metabolite(s).

Resistance of Leishmania donovani to sodium stibogluconate is related to the expression of host and parasite gamma-glutamylcysteine synthetase

Sequencing studies showed that the gamma-glutamylcysteine synthetase (gamma-GCS) heavy chain genes from sodium stibogluconate (SSG)-resistant (SSG-R) and SSG-susceptible (SSG-S) Leishmania donovani strains were identical, indicating that SSG resistance was related to quantitative differences in gamma-GCS expression rather than gene interstrain polymorphisms. In vitro infection of murine macrophages with the SSG-R strain, but not the SSG-S strain, down regulated expression of host gamma-GCS, which would result in a reduction in intramacrophage glutathione (GSH) levels and promote an oxidative intramacrophage environment. This would inhibit, or minimize, the reduction of SSG pentavalent antimony to its more toxic trivalent form. Macrophage studies showed that the SSG-R strain expressed higher levels of gamma-GCS compared to the SSG-S strain, which would result in higher GSH levels, giving increased protection against oxidative stress and facilitating SSG efflux. However a similar differential effect on host and parasite gamma-GCS expression was not obtained when using tissues from infected mice. In this case gamma-GCS expression was organ and strain dependent for both the host and the parasite, indicating that environmental conditions have a profound effect on gamma-GCS expression. Consistent with the proposed mechanism from in vitro studies, increasing tissue GSH levels in the presence of SSG by cotreatment of L. donovani-infected mice with SSG solution and GSH incorporated into nonionic surfactant vesicles was more effective in reducing liver, spleen, and bone marrow parasite burdens than monotherapy with SSG. Together, these results indicate that SSG resistance is associated with manipulation of both host and parasite GSH levels by L. donovani.