Effects of ascorbic acid, glutathione, thiocyanate, and iodide on antimicrobial activity of acidified nitrite

Antibacterial tragacanth gum-based nanocomposite films carrying ascorbic acid antioxidant for bioactive food packaging

Food packaging has a pivotal share to improve protection, safety and shelf-life time of foods and bioproducts. Herein, we prepared bioactive nanocomposite films that composed of tragacanth (TG), polyvinyl alcohol, ZnO nanoparticles (NPs) and ascorbic acid (AA) using glycerol as a plasticizer and citric acid as a cross-linker for food packaging. The SEM images showed a homogenous distribution of ZnO NPs with low aggregation in nanocomposite films. The water solubility of nanocomposite films reduced from 15.65 % to 10.81 with increasing of TG and ZnO NPs contents. The incorporation of AA and ZnO NPs into nanocomposite films improved antioxidant activity from 50 % to 66 % in 95 % ethanolic solution. Also, the nanocomposite films showed good antibacterial activity against Gram-negative and -positive bacteria. Soil degradation rate of nanocomposite films increased from 80 % to 91.46 as the wt% of TG increased. Therefore, prepared nanocomposite films could be employed as a promising candidate for food packaging applications.

Neonatal comorbidities and gasotransmitters

Hydrogen sulfide, nitric oxide, and carbon monoxide are endogenously produced gases that regulate various signaling pathways. The role of these transmitters is complex as constitutive production of these molecules may have anti-inflammatory, anti-microbial, and/or vasodilatory effects whereas induced production or formation of secondary metabolites may lead to cellular death. Given this fine line between friend and foe, therapeutic attenuation of these molecules' production has involved both inhibition of endogenous formation and therapeutic supplementation. All three gases have been implicated as regulators of critical aspects of neonatal physiology, and in turn, comorbidities including necrotizing enterocolitis, hypoxic ischemic encephalopathy, and pulmonary hypertension. In this review, we present current perspectives on these associations, highlight areas where insights remain sparse, and identify areas for potential for future investigations.

The efficacy of topical human amniotic membrane-mesenchymal stem cell-conditioned medium (hAMMSC-CM) and a mixture of topical hAMMSC-CM + vitamin C and hAMMSC-CM + vitamin E on chronic plantar ulcers in leprosy:a randomized control trial

BACKGROUND

Healing of chronic plantar ulcers in leprosy (CPUL) typically takes a long time due to impaired neurological function, thereby reducing the levels of growth factors and cytokines. Cytokines can be found in metabolite products from amniotic membrane stem cells. Chronic ulcers are frequently characterized by high levels of reactive oxygen species. Vitamin E (α-tocopherol) is widely used in skin lesions, owing to its antioxidant and anti-inflammatory properties. Vitamin C also has antioxidant, anti-inflammatory, and collagen synthesis properties which are useful in wound healing. Herein, we compared the effects of topical human amniotic membrane-mesenchymal stem cell-conditioned medium (hAMMSC-CM) alone and with vitamins C and E on healing of CPUL.

METHODS

In this randomized controlled trial, topical agents were applied every 3 days for up to 8 weeks. Ulcer size, side-effects, and possible complications were monitored weekly.

RESULTS

Healing percentage increased each week in all groups. Mean difference in ulcer size was highest in the hAMMSC-CM + vitamin E group, implying better progress of wound healing. There were no side-effects or complications.

CONCLUSIONS

hAMMSC-CM + vitamin E is best for healing of CPUL.

Dietary intake and bio-activation of nitrite and nitrate in newborn infants

Nitrate and nitrite are commonly thought of as inert end products of nitric oxide (NO) oxidation, possibly carcinogenic food additives, or well-water contaminants. However, recent studies have shown that nitrate and nitrite play an important role in cardiovascular and gastrointestinal homeostasis through conversion back into NO via a physiological system involving enterosalivary recirculation, bacterial nitrate reductases, and enzyme-catalyzed or acidic reduction of nitrite to NO. The diet is a key source of nitrate in adults; however, infants ingest significantly less nitrate due to low concentrations in breast milk. In the mouth, bacteria convert nitrate to nitrite, which has gastro-protective effects. However, these nitrate-reducing bacteria are relatively inactive in infants. Swallowed nitrite is reduced to NO by acid in the stomach, affecting gastric blood flow, mucus production, and the gastric microbiota. These effects are likely attenuated in the less acidic neonatal stomach. Systemically, nitrite acts as a reservoir of NO bioactivity that can protect against ischemic injury, yet plasma nitrite concentrations are markedly lower in infants than in adults. The physiological importance of the diminished nitrate→nitrite→NO axis in infants and its implications in the etiology and treatment of newborn diseases such as necrotizing enterocolitis and hypoxic/ischemic injury are yet to be determined.

Isolation, Purification and Evaluation of Antibacterial Agents from Aloe vera

The ethanol, methanol and acetone extracts of Aloe vera gel were studied for their antimicrobial activity against four Gram-positive and Gram-negative bacteria using agar well diffusion method. The extracts showed varied levels of antimicrobial activity against the tested pathogens. The ethanol and methanol extracts showed higher activity while acetone extract, showed least or no activity against most of the tested pathogens. Fractions obtained from the extracts by Thin Layer and Column Chromatography were studied for their antagonistic properties using Spot Assay Technique. Compounds with maximum antibacterial activity isolated from the ethanol and methanol extracts were identified as p – coumaric acid (Mol. wt.165), ascorbic acid (Mol. wt.177 ), pyrocatechol (Mol. wt.110 ) and cinnamic acid (Mol. wt.148), on the basis of Gas Chromatography Mass Spectrometry. The study suggests the antimicrobial activity of the A. vera gel extract to be dependant on the synergistic effect of different compounds. With the broad spectral antimicrobial effect of A. vera gel, it could be further recommended in the treatment of various bacterial diseases.

The Na+/I- symporter mediates active iodide uptake in the intestine

Absorption of dietary iodide, presumably in the small intestine, is the first step in iodide (I(-)) utilization. From the bloodstream, I(-) is actively taken up via the Na(+)/I(-) symporter (NIS) in the thyroid for thyroid hormone biosynthesis and in such other tissues as lactating breast, which supplies I(-) to the newborn in the milk. The molecular basis for intestinal I(-) absorption is unknown. We sought to determine whether I(-) is actively accumulated by enterocytes and, if so, whether this process is mediated by NIS and regulated by I(-) itself. NIS expression was localized exclusively at the apical surface of rat and mouse enterocytes. In vivo intestine-to-blood transport of pertechnetate, a NIS substrate, was sensitive to the NIS inhibitor perchlorate. Brush border membrane vesicles accumulated I(-) in a sodium-dependent, perchlorate-sensitive manner with kinetic parameters similar to those of thyroid cells. NIS was expressed in intestinal epithelial cell line 6, and I(-) uptake in these cells was also kinetically similar to that in thyrocytes. I(-) downregulated NIS protein expression and its own NIS-mediated transport both in vitro and in vivo. We conclude that NIS is functionally expressed on the apical surface of enterocytes, where it mediates active I(-) accumulation. Therefore, NIS is a significant and possibly central component of the I(-) absorption system in the small intestine, a system of key importance for thyroid hormone biosynthesis and thus systemic intermediary metabolism.

Nitric oxide antagonizes the acid tolerance response that protects Salmonella against innate gastric defenses

Background

Reactive nitrogen species (RNS) derived from dietary and salivary inorganic nitrogen oxides foment innate host defenses associated with the acidity of the stomach. The mechanisms by which these reactive species exert antimicrobial activity in the gastric lumen are, however, poorly understood.

Methodology/Principal Findings

The genetically tractable acid tolerance response (ATR) that enables enteropathogens to survive harsh acidity was screened for signaling pathways responsive to RNS. The nitric oxide (NO) donor spermine NONOate derepressed the Fur regulon that controls secondary lines of resistance against organic acids. Despite inducing a Fur-mediated adaptive response, acidified RNS largely repressed oral virulence as demonstrated by the fact that Salmonella bacteria exposed to NO donors during mildly acidic conditions were shed in low amounts in feces and exhibited ameliorated oral virulence. NO prevented Salmonella from mounting a de novo ATR, but was unable to suppress an already functional protective response, suggesting that RNS target regulatory cascades but not their effectors. Transcriptional and translational analyses revealed that the PhoPQ signaling cascade is a critical ATR target of NO in rapidly growing Salmonella. Inhibition of PhoPQ signaling appears to contribute to most of the NO-mediated abrogation of the ATR in log phase bacteria, because the augmented acid sensitivity of phoQ-deficient Salmonella was not further enhanced after RNS treatment.

Conclusions/Significance

Since PhoPQ-regulated acid resistance is widespread in enteric pathogens, the RNS-mediated inhibition of the Salmonella ATR described herein may represent a common component of innate host defenses.

Nitrate and nitrite in Australian leafy vegetables

A market survey of Australian leafy vegetables and a winter and spring experiment with Swiss chard were conducted to examine nitrate and nitrite levels in leaves. The relationship between growth response to nitrogen (N) supply and light level and accumulation of N in leaves was of particular interest. The survey that included 7 types of lettuce and endive (Asteraceae), 6 leafy Asian vegetables (Brassicaceae), and Swiss chard and spinach (Amaranthaceae) showed that fresh leafy vegetables available during a 6-month period on the Australian market can range in nitrate-N from 12 to 1400 mg/kg fresh weight and nitrite-N from 0 to 37.5 mg/kg. Some samples exceeded the limits for nitrate and nitrite based on international food safety standards. The response of Swiss chard to N supply and light was investigated. The accumulation of nitrate in Swiss chard was primarily influenced by increasing N supply and not by light level. Light conditions for all treatments in both the winter and spring experiments exceeded the critical level (~200 μmol/m2.s) required to increase leaf nitrate. Growth and leaf nitrate concentration were higher for spring, associated with average minimum to maximum temperatures of 18–39°C, compared with 14–28°C for winter. Treatment effects on nitrite-N in Swiss chard could not be determined because nitrite was only detected in one-third of plants. The importance of N supply in affecting nitrate accumulation in vegetables is highlighted by the Swiss chard experiments. It confirmed that nitrate accumulation occurs at optimal to supra-optimal nitrate supply, emphasising for growers the undesirable effect of excessive fertiliser use.

Expression of the Na+/I- symporter (NIS) is markedly decreased or absent in gastric cancer and intestinal metaplastic mucosa of Barrett esophagus

Background

The sodium/iodide symporter (NIS) is a plasma membrane glycoprotein that mediates iodide (I^-) transport in the thyroid, lactating breast, salivary glands, and stomach. Whereas NIS expression and regulation have been extensively investigated in healthy and neoplastic thyroid and breast tissues, little is known about NIS expression and function along the healthy and diseased gastrointestinal tract.

Methods

Thus, we investigated NIS expression by immunohistochemical analysis in 155 gastrointestinal tissue samples and by immunoblot analysis in 17 gastric tumors from 83 patients.

Results

Regarding the healthy Gl tract, we observed NIS expression exclusively in the basolateral region of the gastric mucin-producing epithelial cells. In gastritis, positive NIS staining was observed in these cells both in the presence and absence of Helicobacter pylori. Significantly, NIS expression was absent in gastric cancer, independently of its histological type. Only focal faint NIS expression was detected in the direct vicinity of gastric tumors, i.e., in the histologically intact mucosa, the expression becoming gradually stronger and linear farther away from the tumor. Barrett mucosa with junctional and fundic-type columnar metaplasia displayed positive NIS staining, whereas Barrett mucosa with intestinal metaplasia was negative. NIS staining was also absent in intestinalized gastric polyps.

Conclusion

That NIS expression is markedly decreased or absent in case of intestinalization or malignant transformation of the gastric mucosa suggests that NIS may prove to be a significant tumor marker in the diagnosis and prognosis of gastric malignancies and also precancerous lesions such as Barrett mucosa, thus extending the medical significance of NIS beyond thyroid disease.

In vitro killing of nosocomial pathogens by acid and acidified nitrite

Exposure to pH 1 or 2 buffers or acidic gastric contents resulted in the killing of vancomycin-resistant Enterococcus sp., Klebsiella pneumoniae, Staphylococcus aureus, and Candida glabrata but not Clostridium difficile spores. Nitrite enhanced killing under acidic conditions, but significant killing of C. difficile spores required nitrite concentrations above usual physiological levels.

Intragastric generation of antimicrobial nitrogen oxides from saliva--physiological and therapeutic considerations

Salivary nitrite is suggested to enhance the antimicrobial properties of gastric juice by conversion to nitric oxide (NO) and other reactive nitrogen intermediates in the stomach. Intubated patients exhibit extremely low gastric levels of NO, because they do not swallow their saliva. The present investigation was designed to examine the antibacterial effects of human saliva and gastric juice. Furthermore, we studied a new mode of NO delivery, involving formation from acidified nitrite, which could prevent bacterial growth in the gastric juice of intubated patients in intensive care units. The growth of Escherichia coli ATCC 25922 and the formation of NO and nitroso/nitrosyl species were determined after incubation of gastric juice with saliva from healthy volunteers that was rich (nitrate ingestion) or poor (overnight fasting) in nitrite. In a stomach model containing gastric juice from intubated patients, we inserted a catheter with a silicone retention cuff filled with ascorbic acid and nitrite and determined the resulting antibacterial effects on E. coli and Candida albicans. Saliva enhanced the bactericidal effect of gastric juice, especially saliva rich in nitrite. Formation of NO and nitroso/nitrosyl species by nitrite-rich saliva was 10-fold greater than that by saliva poor in nitrite. In our stomach model, E. coli and C. albicans were killed after exposure to ascorbic acid and nitrite. In conclusion, saliva rich in nitrite enhances the bactericidal effects of gastric juice, possibly through the generation of reactive nitrogen intermediates, including NO. Acidified nitrite inside a gas-permeable retention cuff may be useful for restoring gastric NO levels and host defense in critically ill patients.

Sodium-iodide symporter mediates iodide secretion in rat gastric mucosa in vitro

In vivo studies on rats have demonstrated that considerable amounts of iodide are transported from the bloodstream into the gastric lumen. The mechanisms for and functional significance of this transport are poorly understood. Active (driven by Na(+)/K(+)-ATPase) iodide transport into thyroid follicular cells is mediated by the sodium-iodide symporter (NIS), which is also abundantly expressed in gastric mucosa. We aimed to further investigate the iodide transport in gastric mucosa and the possible role of NIS in this transport process. Iodide transport in rat gastric mucosa was studied in vitro in an Ussing chamber system using (125)I as a marker. The system allows measurements in both directions over a mucosal specimen. A considerable transport of iodide (from the serosal to the mucosal side) was established across the gastric mucosa, whereas in the opposite direction (mucosa to serosa), iodide transport was negligible. Sodium perchlorate (NaClO(4)), a competitive inhibitor of NIS, and ouabain, an inhibitor of the Na(+)/K(+)-ATPase, both attenuated gastric iodide transport from the serosal to the mucosal side. To investigate a possible neuroendocrine regulation of the iodide transport identified to occur from the serosal to the mucosal side of the stomach, thyroid-stimulating hormone (TSH), thyrotropin-releasing hormone (TRH), vasoactive intestinal peptide (VIP), histamine, or nitric oxide donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP) was added. None of these substances influenced the iodide transport. We conclude that iodide is actively transported into the gastric lumen and that this transport is at least partly mediated by NIS. Additional investigations are needed to understand the regulation and significance of this transport.