Injury Induced by Chemical Warfare Agents: Characterization and Treatment of Ocular Tissues Exposed to Nitrogen Mustard

PURPOSE. Mustard agents are highly toxic and abundant warfare chemicals, primarily affecting ocular tissues, with no specific treatment antidote. The purpose of the present study was to examine the efficacy of novel metallocomplexes, known to inhibit the formation of highly reactive free radicals, to reduce ocular injury induced by nitrogen mustard (NM). METHODS. One eye in each of 72 rabbits was exposed to 1% to 2% NM. Topical treatment with eye drops of a metallocomplex-either zinc-or gallium-desferrioxamine (Zn/DFO and Ga/DFO)-was compared with treatment with saline, zinc (chloride), or DFO alone. Examiners masked to the treatment groups assessed the extent of ocular injury and the response to treatment using clinical, histologic, and biochemical criteria. RESULTS. Exposure to NM followed by administration of carrier alone (saline) caused severe and long-lasting injury to ocular anterior segment structures. Treatment with either Zn/DFO or Ga/DFO yielded marked protection (52%-64%), including faster healing of corneal epithelial erosions, less scarring and neovascularization, decreased inflammation in the anterior chamber, better maintenance of intraocular pressure, and less severe changes in the iris and lens. These were also associated with better preservation of systemic antioxidant status. Zinc or DFO alone afforded lower levels of protection. No toxic effects of these complexes were observed. CONCLUSIONS. It is suggested that Zn/DFO or Ga/DFO, by virtue of their enhanced ability to infiltrate cells and inhibit transition metal-dependent formation of free radicals through the combined push-pull mechanism, be considered as a basis for treatment of mustard injuries. (Invest Ophthalmol Vis Sci

Protection by Nitric Oxide Donors of Isolated Rat Hearts Is Associated with Activation of Redox Metabolism and Ferritin Accumulation.

Preconditioning (PC) procedures (ischemic or pharmacological) are powerful procedures used for attaining protection against prolonged ischemia and reperfusion (I/R) injury, in a variety of organs, including the heart. The detailed molecular mechanisms underlying the protection by PC are however, complex and only partially understood. Recently, an 'iron-based mechanism' (IBM), that includes de novo ferritin synthesis and accumulation, was proposed to explain the specific steps in cardioprotection generated by IPC. The current study investigated whether nitric oxide (NO), generated by exogenous NO-donors, could play a role in the observed IBM of cardioprotection by IPC. Therefore, three distinct NO-donors were investigated at different concentrations (1-10 μM): sodium nitroprusside (SNP), 3-morpholinosydnonimine (SIN-1) and S-nitroso-N-acetylpenicillamine (SNAP). Isolated rat hearts were retrogradely perfused using the Langendorff configuration and subjected to prolonged ischemia and reperfusion with or without pretreatment by NO-donors. Hemodynamic parameters, infarct sizes and proteins of the methionine-centered redox cycle (MCRC) were analyzed, as well as cytosolic aconitase (CA) activity and ferritin protein levels. All NO-donors had significant effects on proteins involved in the MCRC system. Nonetheless, pretreatment with 10 μM SNAP was found to evoke the strongest effects on Msr activity, thioredoxin and thioredoxin reductase protein levels. These effects were accompanied with a significant reduction in infarct size, increased CA activity, and ferritin accumulation. Conversely, pretreatment with 2 μM SIN-1 increased infarct size and was associated with slightly lower ferritin protein levels. In conclusion, the abovementioned findings indicate that NO, depending on its bio-active redox form, can regulate iron metabolism and plays a role in the IBM of cardioprotection against reperfusion injury

The Loss of Myocardial Benefit following Ischemic Preconditioning Is Associated with Dysregulation of Iron Homeostasis in Diet-Induced Diabetes

<div><p>Whether the diabetic heart benefits from ischemic preconditioning (IPC), similar to the non-diabetic heart, is a subject of controversy. We recently proposed new roles for iron and ferritin in IPC-protection in Type 1-like streptozotocin-induced diabetic rat heart. Here, we investigated iron homeostasis in Cohen diabetic sensitive rat (CDs) that develop hyperglycemia when fed on a high-sucrose/low-copper diet (HSD), but maintain normoglycemia on regular-diet (RD). Control Cohen-resistant rats (CDr) maintain normoglycemia on either diet. The IPC procedure improved the post-ischemic recovery of normoglycemic hearts (CDr-RD, CDr-HSD and CDs-RD). CDs-HSD hearts failed to show IPC-associated protection. The recovery of these CDs-HSD hearts following I/R (without prior IPC) was better than their RD controls. During IPC ferritin levels increased in normoglycemic hearts, and its level was maintained nearly constant during the subsequent prolonged ischemia, but decayed to its baseline level during the reperfusion phase. In CDs-HSD hearts the baseline levels of ferritin and ferritin-saturation with iron were notably higher than in the controls, and remained unchanged during the entire experiment. This unique and abnormal pattern of post-ischemic recovery of CDs-HSD hearts is associated with marked changes in myocardial iron homeostasis, and suggests that iron and iron-proteins play a causative role/s in the etiology of diabetes-associated cardiovascular disorders.</p></div

Infarct sizes of the rat hearts after exposure to the different experimental protocols.

<p>Data are presented as Mean ± SEM.* p < 0.05 versus I/R.</p

Activity of cytosolic aconitase.

<p>Activity of cytosolic aconitase.</p

Experimental protocols.

<p>Experimental protocols.</p

The Loss of Myocardial Benefit following Ischemic Preconditioning Is Associated with Dysregulation of Iron Homeostasis in Diet-Induced Diabetes - Fig 1

<p><b>Three basic experimental protocols (A) and post-ischemic recovery of the WI (B and C).</b> (A) (i) IPC followed by I/R (upper bar); ii) I/R (middle bar); and (iii) continuous perfusion (lower bar). (B and C) Post-ischemic recovery of WI for hearts from Cohen diabetes-resistant (CDr) rats (Panel 1B) and Cohen diabetes-sensitive rats (CDs) (Panel 1C), subjected to I/R without and with prior IPC. Animals were fed on either high sucrose/low copper diet (HSD) or regular (RD) diets. WI was calculated as the product of the Developed Pressure x Heart Rate (DP*HR). The degree of cardioprotection was expressed by as percent (%) ratio of two values: WI at the 120^th minute (completion of the reperfusion phase) and WI at 10^th minute (the last minute of the stabilization phase). Mean ± SEM values are shown; <b>*</b>—p<0.05 in IPC+I/R <i>versus</i> I/R in CDs-RD; ^<b>#</b>—p<0.05 in IPC+I/R <i>versus</i> I/R in CDr-HSD; ^<b>‡</b>—p<0.05 in IPC+I/R <i>versus</i> I/R in CDr-RD.</p

The Methionine-Centered Redox Cycle.

<p>The formation of methionine sulfoxide (MetO) can result from the oxidation of free methionine, or a methionyl residue of a protein. Additional oxidation will generate methionine sulfone (MetO₂), a product that is almost irreversible in biological systems, and can cause protein denaturation. MetO can be reduced by methionine sulfoxide reductases (MsrA or MsrB isoform), through thioredoxin (Trx). Thioredoxin reductase (TrxR) regenerates the oxidized Trx (Trx_ox) via critical components of the cellular redox system, NADP/NADP(H) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159951#pone.0159951.ref032" target="_blank">32</a>].</p

Activities of methionine sulfoxide reductase.

<p>Activities of methionine sulfoxide reductase.</p