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Biomedical subjects

Milton Smith

Publications and source records attributed to Milton Smith.

11 recordsLinked to original sources
PubMed2006

Inhibition of inducible Nitric Oxide Synthase by a mustard gas analog in murine macrophages.

BACKGROUND: 2-Chloroethyl ethyl sulphide (CEES) is a sulphur vesicating agent and an analogue of the chemical warfare agent 2,2'-dichlorodiethyl sulphide, or sulphur mustard gas (HD). Both CEES and HD are alkylating agents that influence cellular thiols and are highly toxic. In a previous publication, we reported that lipopolysaccharide (LPS) enhances the cytotoxicity of CEES in murine RAW264.7 macrophages. In the present investigation, we studied the influence of CEES on nitric oxide (NO) production in LPS stimulated RAW264.7 cells since NO signalling affects inflammation, cell death, and wound healing. Murine macrophages stimulated with LPS produce NO almost exclusively via inducible nitric oxide synthase (iNOS) activity. We suggest that the influence of CEES or HD on the cellular production of NO could play an important role in the pathophysiological responses of tissues to these toxicants. In particular, it is known that macrophage generated NO synthesised by iNOS plays a critical role in wound healing. RESULTS: We initially confirmed that in LPS stimulated RAW264.7 macrophages NO is exclusively generated by the iNOS form of nitric oxide synthase. CEES treatment inhibited the synthesis of NO (after 24 hours) in viable LPS-stimulated RAW264.7 macrophages as measured by either nitrite secretion into the culture medium or the intracellular conversion of 4,5-diaminofluorescein diacetate (DAF-2DA) or dichlorofluorescin diacetate (DCFH-DA). Western blots showed that CEES transiently decreased the expression of iNOS protein; however, treatment of active iNOS with CEES in vitro did not inhibit its enzymatic activity CONCLUSION: CEES inhibits NO production in LPS stimulated macrophages by decreasing iNOS protein expression. Decreased iNOS expression is likely the result of CEES induced alteration in the nuclear factor kappa B (NF-kappaB) signalling pathway. Since NO can act as an antioxidant, the CEES induced down-regulation of iNOS in LPS-stimulated macrophages could elevate oxidative stress. Since macrophage generated NO is known to play a key role in cutaneous wound healing, it is possible that this work has physiological relevance with respect to the healing of HD induced skin blisters.

Animals↗
PubMed2006

Hydrogen storage properties of metal nitroprussides M[Fe(CN)5NO], (M = Co, Ni).

The volumetric hydrogen adsorption isotherms of two isostructural dehydrated cubic metal nitroprussides M[Fe(CN)5NO] (M = Co2+, Ni2+) have been measured up to a pressure of 760 Torr at 77 and 87 K. These materials are among the most efficient H2 sorbents based on porous coordination polymers reported to date. The H2 uptake in both materials is approximately 1.6 wt % at 77 K and 760 torr. These H2 capacities match those reported recently in the structurally related M3[Co(CN)6]2 compounds and are approximately 25% higher than those reported for Zn4O(1,4-benzenedicarboxylate)3 under the same conditions of temperature and pressure. The isosteric heats of H2 adsorption calculated from the 77 and 87 K isotherms for both materials were found to vary from approximately 7.5 kJ/mol at 0.40 wt % coverage to approximately 5.5 kJ/mol at 1.2 wt % coverage. The N2 BET surface areas were determined to be 634 m2/g and 523 m2/g for M = Ni and M = Co, respectively.

Journal Article↗
PubMed2006

Modulation of the expression of superoxide dismutase gene in lung injury by 2-chloroethyl ethyl sulfide, a mustard analog.

Mustard gas exposure causes inflammatory lung diseases. Many inflammatory lung diseases are associated with oxidative stress. Reactive oxygen species (ROS) are involved in the maintenance of physiological functions. In tissues, it is therefore essential to maintain a steady-state level of antioxidant activity to allow both for the physiological functions of ROS to proceed and at the same time preventing tissue damage. We have recently reported that mustard gas exposure decreases the overall activity of superoxide dismutase (SOD). In the present study, we investigated the effects of mustard gas on each of the three isozymes: SOD-1 (Cu/Zn), SOD-2 (Mn), and SOD-3 (extracellular). Adult guinea pigs were intratracheally injected single doses of 2-chloroethyl ethyl sulfide (CEES) (2 mg/kg body weight) in ethanol. Control animals were injected with vehicle in the same way. The animals were sacrificed after 7 days, and lungs were removed after perfusion with physiological saline. Lung injury was established by measuring the leakage of iodinated-BSA into lung tissue. Mustard gas exposure caused a significant increase in the activity of SOD-1 (35%). However, the SOD-3 activity which is the predominant type in lung was significantly decreased (62%), whereas no change was observed in SOD-2 activity. Thus the decrease in the total activity of SOD was primarily due to the SOD-3 isozyme. Northern blot analysis indicated 3.5-fold increased expression of SOD-1 in mustard gas exposed lung, but no significant change in the expression of SOD-2 and SOD-3 was observed. Mustard gas exposure did not cause mutation in the coding region of SOD-1 gene while causing modulation in expression levels. The protein levels of SOD-1, SOD-2, and SOD-3 were not altered significantly in the mustard gas exposed lung. Our results indicate that the overall decrease in the activity of SOD by mustard gas exposure is probably mediated by direct inactivation of the SOD-3 gene or the enzyme itself. This decrease in the activity of SOD-3 may be due to the cleavage of active form of the protein to an inactive form. The existence of active and inactive forms of SOD-3 as a result of shifts in Cys-Cys disulfide bonding has been described in human, recently. Studies are underway in our laboratory to investigate whether mustard gas induced inactivation of SOD-3 in lung is similarly mediated by a change in Cys-Cys disulfide bonding.

Animals↗
PubMed2005

Decrease in brain POMC mRNA expression and onset of obesity in guinea pigs exposed to 2-chloroethyl ethyl sulfide, a mustard analogue.

The full spectrum of physiological effects resulting from exposure to sulfur mustard and its analogs is currently unknown. In a guinea pig model, initially selected to study the role of an inflammatory cytokine cascade in mustard gas induced lung injury, we observed significant body weight gain in guinea pigs exposed to an intratracheally injected single dose of 2-chloroethyl ethyl sulfide, a mustard analog. The body weight gain was not associated with any apparent change in appetite. To further elucidate a molecular basis for the observed weight gain, we evaluated candidate genes for the obese phenotype by quantitative RT-PCR. We observed a time- and dose-dependent decrease in guinea pig pro-opiomelanocortin (POMC) message following treatment with mustard gas. This reduction in POMC message is consistent with the onset of obesity in the animals. We hypothesize that the POMC melanocortin pathway provides a mechanistic basis for the observed effects of sulfur mustard on body weight.

Animals↗
PubMed2005

Inhibition of cholinephosphotransferase activity in lung injury induced by 2-chloroethyl ethyl sulfide, a mustard analog.

Exposure to mustard gas causes inflammatory lung diseases including acute respiratory distress syndrome (ARDS). A defect in the lung surfactant system has been implicated as a cause of ARDS. A major component of lung surfactant is dipalmitoyl phosphatidylcholine (DPPC) and the major pathway for its synthesis is the cytidine diphosphocholine (CDP-choline) pathway. It is not known whether the ARDS induced by mustard gas is mediated by its direct effects on some of the enzymes in the CDP-choline pathway. In the present study we investigated whether mustard gas exposure modulates the activity of cholinephosphotransferase (CPT) the terminal enzyme by CDP-choline pathway. Adult guinea pigs were intratracheally infused with single doses of 2-chloroethyl ethyl sulfide (CEES) (0.5 mg/kg b.wt. in ethanol). Control animals were injected with vehicles only. The animals were sacrificed at different time and the lungs were removed after perfusion with physiological saline. CPT activity increased steadily up to 4 h and then decreased at 6 h and stabilized at 7 days in both mitochondria and microsomes. To determine the dose-dependent effect of CEES on CPT activity we varied the doses of CEES (0.5-6.0 mg/kg b.wt.) and sacrificed the animals at 1 h and 4 h. CPT activity showed a dose-dependent increase of up to 2.0 mg/kg b.wt. of CEES in both mitochondria and microsomes then decreased at 4.0 mg/kg b.wt. For further studies we used a fixed single dose of CEES (2.0 mg/kg b.wt.) and fixed exposure time (7 days). Lung injury was determined by measuring the leakage of iodinated-bovine serum albumin into lung tissue and expressed as the permeability index. CEES exposure (2.0 mg/kg b.wt. for 7 days) caused a significant decrease of both CPT gene expression (approximately 1.7-fold) and activity (approximately 1.5-fold) in the lung. This decrease in CPT activity was not associated with any mutation of the CPT gene. Previously we reported that CEES infusion increased the production of ceramides which are known to modulate PC synthesis. To determine whether ceramides affect microsomal CPT activity the lung microsomal fraction was incubated with different concentrations of C(2)-ceramide prior to CPT assay. CPT activity decreased significantly with increasing dose and time. The present study indicates that CEES causes lung injury and significantly decreases CPT gene expression and activity. This decrease in CPT activity was not associated with any mutation of the CPT gene is probably mediated by accumulation of ceramides. CEES induced ceramide accumulation may thus play an important role in the development of ARDS by modulating CPT enzyme.

Animals↗
PubMed2005

Interferon alfacon-1 and ribavirin versus interferon alpha-2b and ribavirin in the treatment of chronic hepatitis C.

Despite advances in the therapy of chronic hepatitis C, a large number of patients do not respond to current therapies. The study objective was to assess whether a combination of interferon (IFN) alfacon-1 and ribavirin improves the response rate compared with a combination of INF alpha-2b and ribavirin in chronic hepatitis C subjects. The study was designed as an open-label, prospective, randomized, controlled study; 128 subjects with chronic hepatitis C were randomized to INF alfacon-1, 15 microg three times per week, plus ribavirin, 1 g/day, or IFN-alpha2b, 3 million units three times per week, plus ribavirin, 1 g/day for 48 weeks. The end point of the study was a sustained viral response, defined as undetectable HCV RNA at 24 weeks post 48 weeks of treatment. Overall, 57% of subjects in the INF alfacon-1/ribavirin group achieved a sustained antiviral response, compared with 40% of subjects in the IFN-alpha2b/ribavirin group (P = 0.052). In the subset of subjects with a high viral load, HCV RNA was successfully eradicated in more individuals who received INF alfacon-1/ribavirin than subjects who received IFN-alpha2b/ribavirin (57 versus 31%; P = 0.025). Among individuals with genotype 1 and a high viral load, the sustained antiviral response was significantly higher with INF alfacon-1/ribavirin than with IFN-alpha2b/ribavirin (46 versus 14%; P = 0.019). Adverse events were similar in both treatment groups. In conclusion, this study demonstrated that the combination of INF alfacon-1 and ribavirin provides a significantly better treatment response compared with the combination of IFN-alpha2b and ribavirin in chronic HCV subjects infected with genotype 1 and a high viral RNA load.

Adult↗
PubMed2004

Microporous metal organic materials: promising candidates as sorbents for hydrogen storage.

Advancement in hydrogen storage techniques represents one of the most important areas of today's materials research. While extensive efforts have been made to the existing techniques, there is no viable storage technology capable of meeting the DOE cost and performance targets at the present time. New materials with significantly improved hydrogen adsorption capability are needed. Microporous metal coordination materials (MMOM) are promising candidates for use as sorbents in hydrogen adsorption. These materials possess physical characteristics similar to those of single-walled carbon nanotubes (SWNTs) but also exhibit a number of improved features. Here, we report a novel MMOM structure and its room-temperature hydrogen adsorption properties.

Journal Article↗
PubMed2004

Therapeutic uses of antioxidant liposomes.

This review will focus on the therapeutic uses of antioxidant liposomes. Antioxidant liposomes have a unique ability to deliver both lipid- and water-soluble antioxidants to tissues. This review will detail the varieties of antioxidants which have been incorporated into liposomes, their modes of administration, and the clinical conditions in which antioxidant liposomes could play an important therapeutic role. Antioxidant liposomes should be particularly useful for treating diseases or conditions in which oxidative stress plays a significant pathophysiological role because this technology has been shown to suppress oxidative stress. These diseases and conditions include cancer, trauma, irradiation, retinotherapy or prematurity, respiratory distress syndrome, chemical weapon exposure, and pulmonary infections.

Animals↗
PubMed2003

Lipopolysaccharide enhances the cytotoxicity of 2-chloroethyl ethyl sulfide.

BACKGROUND: The bacterial endotoxin, lipopolysaccharide (LPS), is a well-characterized inflammatory factor found in the cell wall of Gram-negative bacteria. In this investigation, we studied the cytotoxic interaction between 2-chloroethyl ethyl sulfide (CEES or ClCH2CH2SCH2CH3) and LPS using murine RAW264.7 macrophages. CEES is a sulfur vesicating agent and is an analog of 2,2'-dichlorodiethyl sulfide (sulfur mustard). LPS is a ubiquitous natural agent found in the environment. The ability of LPS and other inflammatory agents (such as TNF-alpha and IL-1beta) to modulate the toxicity of CEES is likely to be an important factor in the design of effective treatments. RESULTS: RAW 264.7 macrophages stimulated with LPS were found to be more susceptible to the cytotoxic effect of CEES than unstimulated macrophages. Very low levels of LPS (20 ng/ml) dramatically enhanced the toxicity of CEES at concentrations greater than 400 microM. The cytotoxic interaction between LPS and CEES reached a maximum 12 hours after exposure. In addition, we found that tumor necrosis factor-alpha (TNF-alpha) and interleukin-1-beta (IL-1-beta) as well as phorbol myristate acetate (PMA) also enhanced the cytotoxic effects of CEES but to a lesser extent than LPS. CONCLUSION: Our in vitro results suggest the possibility that LPS and inflammatory cytokines could enhance the toxicity of sulfur mustard. Since LPS is a ubiquitous agent in the natural environment, its presence is likely to be an important variable influencing the cytotoxicity of sulfur mustard toxicity. We have initiated further experiments to determine the molecular mechanism whereby the inflammatory process influences sulfur mustard cytotoxicity.

Adjuvants, Immunologic↗