Surfactant administration reduces testicular ischemia-reperfusion injury

Amelioration of lipopeptide biosurfactants for enhanced antibacterial and biocompatibility through molecular antioxidant property by methoxy and carboxyl moieties

Biosurfactants having surface-active biomolecules have been the cynosure in environment research due to their vast application. However, the lack of information about their low-cost production and detailed mechanistic biocompatibility limits the applicability. The study explores techniques for the production and design of low-cost, biodegradable, and non-toxic biosurfactants from Brevibacterium casei strain LS14 and excavates the mechanistic details of their biomedical properties like antibacterial effects and biocompatibility. Taguchi's design of experiment was used to optimize for enhancing biosurfactant production by optimal factor combinations like Waste glycerol (1%v/v), peptone (1%w/v), NaCl 0.4% (w/v), and pH 6. Under optimal conditions, the purified biosurfactant reduced the surface tension to 35 mN/m from 72.8 mN/m (MSM) and a critical micelle concentration of 25 mg/ml was achieved. Spectroscopic analyses of the purified biosurfactant using Nuclear Magnetic Resonance suggested it as a lipopeptide biosurfactant. The evaluation of mechanistic antibacterial, antiradical, antiproliferative, and cellular effects indicated the efficient antibacterial activity (against Pseudomonas aeruginosa) of biosurfactants due to free radical scavenging activity and oxidative stress. Moreover, the cellular cytotoxicity was estimated by MTT and other cellular assays revealing the phenomenon as the dose-dependent induction of apoptosis due to free radical scavenging with an LC50 of 55.6 ± 2.3 mg/ml.

Effect of Bottlebrush Poloxamer Architecture on Binding to Liposomes

Poloxamers─triblock copolymers consisting of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO)─have demonstrated cell membrane stabilization efficacy against numerous types of stress. However, the mechanism responsible for this stabilizing effect remains elusive, hindering engineering of more effective therapeutics. Bottlebrush polymers have a wide parameter space and known relationships between architectural parameters and polymer properties, enabling their use as a tool for mechanistic investigations of polymer-lipid bilayer interactions. In this work, we utilized a versatile synthetic platform to create novel bottlebrush analogues to poloxamers and then employed pulsed-field-gradient NMR and an in vitro osmotic stress assay to explore the effect of bottlebrush architectural parameters on binding to, and protection of, model phospholipid bilayers. We found that the binding affinity of a bottlebrush poloxamer (BBP) (B-E₁₀⁴³P₅¹⁵, M_n ≈ 26 kDa) is about 3 times higher than a linear poloxamer with a similar composition and number of PPO units (L-E₉₃P₅₄E₉₃, M_n ≈ 11 kDa). Furthermore, BBP binding is sensitive to overall molecular weight, side-chain length, and architecture (statistical versus block). Finally, all tested BBPs exhibit a protective effect on cell membranes under stress at sub-μM concentrations. As the factors controlling membrane affinity and protection efficacy of bottlebrush poloxamers are not understood, these results provide important insight into how they adhere to and stabilize a lipid bilayer surface.

Long-term effects of orchiopexy and orchiectomy on the testes of rats with testicular torsion

INTRODUCTION

Ischemia/reperfusion injury occurs after testicular torsion, levels of free oxygen radicals and inflammatory cytokines are increased in both the torsional and contralateral testis, leading to testicular injury.

OBJECTIVE

The present study investigated whether orchiopexy or orchiectomy after testicular torsion was superior in terms of fertility potential in the long term.

STUDY DESIGN

Following 720°, 4 h left testicular torsion, orchiectomy or orchiopexy was performed on 84 rats, which were then sacrificed and evaluated for testicular function at day 1, at 3 months and 6 months (n = 14 per group). An additional 14 rats were in the control group.

RESULTS

Follicle stimulating hormone (FSH), luteinizing hormone (LH), and testosterone levels were significantly lower in the orchiopexy group than the orchiectomy and control groups after 3 months. However, there were no significant differences in hormone parameters among the three groups after 6 months. The hormone levels, Johnsen score, seminiferous tubule diameter, and inducible nitric oxide synthase (iNOS) expression at 3 and 6 months were not significantly different between the orchiectomy group and controls. Histopathological analyses at 3 and 6 months indicated significant decreases in Johnsen score and seminiferous tubule diameter in the ipsilateral testis in the orchiopexy group. At 3 months, the level of iNOS expression in the contralateral testis was significantly lower in the orchiopexy group than in other groups. At 6 months, however, it was not significantly different between the orchiopexy and control groups. There were no significant differences in iNOS expression at 3 or 6 months in the orchiectomy group compared to controls.

DISCUSSION

The ipsilateral testis in the orchiopexy group began to atrophy at 3 months, and the degree of atrophy became more evident at 6 months. The level of iNOS expression was low in the bilateral testis at 3 months in the orchiopexy group, and sperm in the contralateral testis were not yet functionally healthy. The level of iNOS expression in the ipsilateral testis decreased further at 6 months in the orchiopexy group, while that in the contralateral testis returned to the normal level.

CONCLUSION

Testicular functions were restored faster after orchiectomy compared to orchiopexy following testicular torsion. However, follow-up of the rats for 6 months demonstrated that orchiopexy or orchiectomy procedures conducted on the testicular torsion had no effect on future fertility potential after 4 h of torsion.

The potential protective and therapeutic effects of platelet-rich plasma on ischemia/reperfusion injury following experimental torsion/detorsion of testis in the Albino rat model

AIMS

This study was designed to evaluate the protective and therapeutic efficacy of platelet-rich plasma (PRP) against testicular degeneration and germ cell apoptosis after induced spermatic cord torsion/detorsion (TD) in rats.

MATERIALS

Forty rats were allocated into 5 groups: 1) control, 2) short torsion/detorsion (STD), 3) long torsion detorsion (LTD), 4) protective (PRP/P) and 5) treatment (PRP/T). Testicular ischemia was induced by twisting the right testis 1080° clockwise for 2.5 h. PRP (10 μl) was injected intra-testicular 5 min before (PRP/P) and 3 h after (PRP/T) detorsion. At the end of the experiment, rats were euthanized at 2, 30, 2, and 30 days for groups 2-5 respectively. Nitric oxide, malondialdehyde, catalase, total antioxidant capacity, reduced glutathione, glutathione-S-transferase, interleukin1 beta, tumor necrosis factor, caspase-3, and B-cell lymphoma 2 expressions were assessed in the testes. Moreover, histological examination was performed.

KEY FINDINGS

PRP treatment significantly mitigated the torsion-detorsion induced testicular degeneration. Particularly, by improving the state of oxidative stress (NO, P = 0.0001) and antioxidant markers (TAC, GSH, GST, P = 0.0001-0.01) and decreasing the expression of IL-1β, TNF-α and cas 3 and increase the BCL2 fold changes (P = 0.0001). The protective use of PRP is superior to the therapeutic use of PRP in the restoration of the testicular histoarchitecture following TD.

SIGNIFICANCE

This study illustrates the cyto-protective role of PRP against TD induced testicular cell injury that highlight possible application of PRP as a complementary therapy in different testicular degenerative diseases which might attribute to its ability to ameliorate the oxidative stress and inhibit induced apoptosis.

Cell salvage in acute and chronic wounds: a potential treatment strategy. Experimental data and early clinical results

On 9 May 2018, the authors took part in a closed panel discussion on the impact of cell salvage in acute and chronic wounds. The goal was to deliberate the possible use of plurogel micelle matrix (PMM) as a new treatment strategy for wound healing and the authors openly shared their experiences, thoughts, experimental data and early clinical results. The outcome of the panel discussion has been abridged in this paper. The cell membrane consists of a lipid bilayer, which provides a diffusion barrier separating the inside of a cell from its environment. Cell membrane injury can result in acute cellular necrosis when defects are too large and cannot be resealed. There is a potential hazard to the body when these dying cells release endogenous alarm signals referred to as 'damage (or danger) associated molecular patterns' (DAMPs), which trigger the innate immune system and modulate inflammation. Cell salvage by membrane resealing is a promising target to ensure the survival of the individual cell and prevention of further tissue degeneration by inflammatory processes. Non-ionic surfactants such as poloxamers, poloxamines and PMM have the potential to resuscitate cells by inserting themselves into damaged membranes and stabilising the unstable portions of the lipid bilayers. The amphiphilic properties of these molecules are amenable to insertion into cell wall defects and so can play a crucial, reparative role. This new approach to cell rescue or salvage has gained increasing interest as several clinical conditions have been linked to cell membrane injury via oxidative stress-mediated lipid peroxidation or thermal disruption. The repair of the cell membrane is an important step in salvaging cells from necrosis to prevent further tissue degeneration by inflammatory processes. This is applicable to acute burns and chronic wounds such as diabetic foot ulcers (DFUs), chronic venous leg ulcers (VLUs), and pressure ulcers (PUs). Experimental data shows that PMM is biocompatible and able to insert itself into damaged membranes, salvaging their barrier function and aiding cell survival. Moreover, the six case studies presented in this paper reveal the potential of this treatment strategy.

Mode of action of poloxamer-based surfactants in wound care and efficacy on biofilms

Surfactants are widely used as detergents, emulsifiers, wetting agents, foaming agents, and dispersants in both the food and oil industry. Their use in a clinical setting is also common, particularly in wound care. Complicated or chronic wounds show clinical signs of delayed healing, persistent inflammation, and the production of non-viable tissue. These types of wounds also present challenges such as infection and potentially house antimicrobial-tolerant biofilms. The use of wound cleansers to aid cleaning and debridement of the wound is essential. A large proportion of skin and wound cleansers contain surfactants but there is only a small amount of data that shows the effectiveness of them in the enhancement of wound closure. This review paper aims to explore the available literature surrounding the use and mode of action of surfactants in wound healing, in particular Poloxamer 188 (Pluronic F-68) and Poloxamer 407 (Pluronic F-127), and also uncover the potential mechanisms behind the enhancement of wound healing and comparison to other surfactants used in wound care. Furthermore, the presence of a microbial biofilm in the wound is a significant factor in delayed wound healing. Therefore, the effect of clinically used surfactants on biofilms will be discussed, with emphasis on poloxamer-based surfactants.

Quantifying Binding of Ethylene Oxide-Propylene Oxide Block Copolymers with Lipid Bilayers

Block copolymers composed of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) have been widely used in cell membrane stabilization and permeabilization. To explore the mechanism of interaction between PPO-PEO block copolymers and lipid membranes, we have investigated how polymer structure influences the polymer-lipid bilayer association by varying the overall molecular weight, the hydrophobic and hydrophilic block lengths, and the end-group structure systematically, using 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) unilamellar liposomes as model membranes. Pulsed-field-gradient NMR (PFG-NMR) was employed to probe polymer diffusion in the absence and presence of liposomes. The echo decay curves of free polymers in the absence of liposomes are single exponentials, indicative of simple translational diffusion, while in the presence of liposomes, the decays are biexponential, with the slower decay corresponding to polymers bound to liposomes. The binding percentage of polymer to the liposome was quantified by fitting the echo decay curves to a biexponential model. The NMR experiments show that increasing the total molecular weight and hydrophobicity of the polymer can significantly enhance the polymer-lipid bilayer association, as the binding percentage and liposome surface coverage both increase. We hypothesize that the hydrophobic PPO block inserts into the lipid bilayer due to the fact that little molecular exchange between bound and free polymers occurs on the time scale of the diffusion experiments. Additionally, as polymer concentration increases, the liposome surface coverage increases and approaches a limit. These results demonstrate that PFG-NMR is a simple yet powerful method to quantify interactions between polymers and lipid bilayers.

The Pentablock Amphiphilic Copolymer T1107 Prevents Aggregation of Denatured and Reduced Lysozyme

Aggregation of denatured or unfolded proteins establishes a large energy barrier to spontaneous recovery of protein form and function following traumatic injury, tissue cryopreservation, and biopharmaceutical storage. Some tissues utilize small heat shock proteins (sHSPs) to prevent irreversible aggregation, which allows more complex processes to refold or remove the unfolded proteins. It is postulated that large, amphiphilic, and biocompatible block copolymers can mimic sHSP function. Reduced and denatured hen egg white lysozyme (HEWL) is used as a model aggregating protein. The poloxamine T1107 prevents aggregation of HEWL at 37 °C by three complimentary measures. Structural analysis of denatured HEWL reveals a partially folded conformation with preserved or promoted beta-sheet structures only in the presence of T1107. The physical association of T1107 with denatured HEWL, and the ability to prevent aggregation, is linked to the critical micelle temperature of the polymer. The results suggest that T1107, or a similar amphiphilic block copolymer, can find use as a synthetic chaperone to augment the innate molecular repair mechanisms of natural cells.

Reverse poly(butylene oxide)–poly(ethylene oxide)–poly(butylene oxide) block copolymers with lengthy hydrophilic blocks as efficient single and dual drug-loaded nanocarriers with synergistic toxic effects on cancer cells

Reverse triblock copolymer micelles with lengthy polyethylene oxide blocks as efficient sustained dual drug-loaded nanocarriers.

Polymers influencing transportability profile of drug

Drug release from various polymers is generally governed by the type of polymer/s incorporated in the formulation and mechanism of drug release from polymer/s. A single polymer may show one or more mechanisms of drug release out of which one mechanism is majorly followed for drug release. Some of the common mechanisms of drug release from polymers were, diffusion, swelling, matrix release, leaching of drug, etc. Mechanism or rate of drug release from a polymer or a combination of polymers can be predicted by using different computational methods or models. These models were capable of predicting drug release from its dosage form in advance without actual formulation and testing of drug release from dosage form. Quantitative structure-property relationship (QSPR) is an important tool used in the prediction of various physicochemical properties of actives as well as inactives. Since last several decades QSPR has been applied in new drug development for reducing the total number of drugs to be synthesized, as it involves a selection of the most desirable compound of interest. This technique was also applied in predicting in vivo performance of drug/s for various parameters. QSPR serves as a predictive tool to correlate structural descriptors of molecules with biological as well as physicochemical properties. Several researchers have contributed at different extents in this area to modify various properties of pharmaceuticals. The present review is focused on a study of different polymers that influence the transportability profiles of drugs along with the application of QSPR either to study different properties of polymers that regulate drug release or in predicting drug transportability from different polymer systems used in formulations.

Desferrioxamine effectively attenuates testicular tissue at the end of 3 h of ischemia but not in an equal period of reperfusion

OBJECTIVE

To investigate the effect of desferrioxamine (DFX) on ipsilateral and contralateral testis damage caused by experimental testis torsion and detorsion.

MATERIALS AND METHODS

Forty rats were divided into five groups (n = 8): control, torsion (T), torsion + desferrioxamine (T + DFX), torsion/detorsion (T/D), and torsion/detorsion + desferrioxamine (T/D + DFX). The right testes of the rats were subjected to torsion and detorsion for 3 h each. Thirty minutes before the application of torsion and detorsion, DFX (100 mg/kg) was administered intramuscularly. Blood samples and testicular tissues were examined using specific biochemical and histopathological methods.

RESULTS

Ipsilateral and contralateral testis tissue glutathione levels in the T group decreased compared with the control and T + DFX groups. Plasma glutathione peroxidase activity in the T, T/D, and T/D + DFX groups was lower than in the control group. Plasma catalase activity in the T and T/D groups decreased compared with the control group. Ipsilateral mean seminiferous tubule diameter of the T group was lower than that of the T + DFX group. The ipsilateral mean testis biopsy scores in the T and T/D groups were lower than in the control group.

CONCLUSION

The administration of DFX prior to torsion may be useful only for preventing ischemic damage in ipsilateral and contralateral testes.

Protective effect of Salvia miltiorrhiza aqueous extract on myocardium oxidative injury in ischemic-reperfusion rats

Salvia miltiorrhiza has strong antioxidative activity. They may have a strong potential as cardioprotective agents in ischemic-reperfusion injury. Experiments were carried out in Sprague-Dawley rats with myocardium ischemia reperfusion (IR). Myocardial injuries during IR were determined by changes in electrocardiogram analysis of arrhythmias, antioxidant enzyme activities, AST, CK-MB, lactate dehydrogenase (LDH) levels, and myocyte apoptosis. Results showed that S. miltiorrhiza aqueous extract (SAME) pre-treatment significantly decreased the ST-segment (ΣST120) and myocardium MDA, AST, CK-MB, lactate dehydrogenase (LDH) levels, increased myocardium antioxidant enzyme activities, and inhibit myocardium cell apoptosis. Furthermore, the SAME pre-treatment significantly upregulated p-JAK2 and p-STAT3 protein expression, decreased myocardium TNF-α and IL-6 concentrations in IR rats. The levels of TNF-α and IL-6 were positively correlated with the changes in myocardium p-JAK2 and p-STAT3 protein expression levels in IR rats. It can be concluded that the SAME pre-treatment has anti-ischemic and anti-apoptosis activity in heart IR rats. SAME pre-treatment protects heart against IR injury, at least in part, through its stimulating effects on injury-induced deactivation of JAK2/STAT3 signaling pathway.

Poloxamer 188 protects neurons against ischemia/reperfusion injury through preserving integrity of cell membranes and blood brain barrier

Poloxamer 188 (P188), a multiblock copolymer surfactant, has been shown to protect against ischemic tissue injury of cardiac muscle, testes and skeletal muscle, but the mechanisms have not been fully understood. In this study, we explored whether P188 had a protective effect against cerebral ischemia/reperfusion injury and its underlying mechanisms. The in vivo results showed that P188 significantly reduced the infarct volume, ameliorated the brain edema and neurological symptoms 24 h after ischemia/reperfusion. In the long-term outcome study, P188 markedly alleviated brain atrophy and motor impairments and increased survival rate in 3 weeks of post stroke period. Additionally, P188 protected cultured hippucampal HT22 cells against oxygen-glucose deprivation and reoxygenation (OGD/R) injury. The ability in membrane sealing was assessed with two fluorescent membrane-impermeant dyes. The results showed that P188 treatment significantly reduced the PI-positive cells following ischemia/reperfusion injury and repaired the HT22 cell membrane rupture induced by Triton X-100. In addition, P188 inhibited ischemia/reperfusion-induced activation of matrix metalloproteinase (MMP)-9 and leakage of Evans blue. Therefore, the present study concludes that P188 can protect against cerebral ischemia/reperfusion injury, and the protection involves multi-mechanisms in addition to the membrane resealing.

Affinity for, and localization of, PEG-functionalized silica nanoparticles to sites of damage in an ex vivo spinal cord injury model

Background

Traumatic spinal cord injury (SCI) leads to serious neurological and functional deficits through a chain of pathophysiological events. At the molecular level, progressive damage is initially revealed by collapse of plasma membrane organization and integrity produced by breaches. Consequently, the loss of its role as a semi-permeable barrier that generally mediates the regulation and transport of ions and molecules eventually results in cell death. In previous studies, we have demonstrated the functional recovery of compromised plasma membranes can be induced by the application of the hydrophilic polymer polyethylene glycol (PEG) after both spinal and brain trauma in adult rats and guinea pigs. Additionally, efforts have been directed towards a nanoparticle-based PEG application.

The in vivo and ex vivo applications of PEG-decorated silica nanoparticles following CNS injury were able to effectively and efficiently enhance resealing of damaged cell membranes.

Results

The possibility for selectivity of tetramethyl rhodamine-dextran (TMR) dye-doped, PEG-functionalized silica nanoparticles (TMR-PSiNPs) to damaged spinal cord was evaluated using an ex vivo model of guinea pig SCI. Crushed and nearby undamaged spinal cord tissues exhibited an obvious difference in both the imbibement and accumulation of the TMR-PSiNPs, revealing selective labeling of compression-injured tissues.

Conclusions

These data show that appropriately functionalized nanoparticles can be an efficient means to both 1.) carry drugs, and 2.) apply membrane repair agents where they are needed in focally damaged nervous tissue.

Nature of interactions between PEO-PPO-PEO triblock copolymers and lipid membranes: (I) effect of polymer hydrophobicity on its ability to protect liposomes from peroxidation

PEO-PPO-PEO triblock copolymers have opposing effects on lipid membrane integrity: they can behave either as membrane sealants or as membrane permeabilizers. To gain insights into their biomembrane activities, the fundamental interactions between a series of PEO-based polymers and phospholipid vesicles were investigated. Specifically, the effect of copolymer hydrophobicity on its ability to prevent liposomes from peroxidation was evaluated, and partitioning free energy and coefficient involved in the interactions were derived. Our results show that the high degree of hydrophilicity is a key feature of the copolymers that can effectively protect liposomes from peroxidation and the protective effect of the copolymers stems from their adsorption at the membrane surface without penetrating into the bilayer core. The origin of this protective effect induced by polymer absorption is attributed to the retardation of membrane hydration dynamics, which is further illustrated in the accompanying study on dynamic nuclear polarization (DNP)-derived hydration dynamics (Cheng, C.-Y.; Wang, J.-Y.; Kausik, R.; Lee, K. Y. C.; Han S. Biomacromolecules, 2012, DOI: 10.1021/bm300848c).

Protective role of natural antioxidant supplementation on testicular tissue after testicular torsion and detorsion

OBJECTIVES

To investigate the impact of garlic extract (GE), which is known for its antioxidant activity, on a testicular torsion/detorsion model in animals and to help understand how to prevent both ischemic and reperfusion injuries after testicular torsion and detorsion.

MATERIAL AND METHODS

Six groups of rats (n=7 in each group) were used. The animals in the control group (Group I) did not receive any treatment. The animals in the sham group (Group II) underwent scrotal incision and testicular fixation only. The animals in Groups III-VI underwent 720 degrees of left testicular torsion for 2 h; subsequent detorsion was performed for 2h in Groups IV and VI only. Animals in Groups V and VI were treated exactly the same as those in Groups III and IV, respectively except that they were pretreated with oral GE for 5 days at a dosage of 5 ml/kg. Both testicles in all rats were removed and tissue malondialdehyde (MDA) levels and enzymatic activities of xanthine oxidase (XO) were studied, in addition to a histological evaluation after hematoxylin-eosin staining.

RESULTS

Testicular MDA levels and XO activities were higher in Group III compared to Group II (p<0.05). Pretreatment with GE prevented these increases. Detorsion caused more damage and resulted in a further increase in MDA levels but MDA levels were not increased in animals pretreated with GE. Histologically, torsion caused some separation between germinative cells in the seminiferous tubules, which became much more prominent in Group IV and was attenuated by GE pretreatment. There were no significant changes in any of the above-mentioned enzymatic activities or histopathologic changes in the contralateral testicle in any of the groups.

CONCLUSIONS

We believe that both testicular torsion and detorsion result in testicular tissue damage by means of lipid peroxidation, which is evident by an increase in the tissue levels of MDA. Dietary supplementation with GE seems to attenuate the generation of toxic free radicals, as evidenced indirectly by low tissue MDA levels.

Treatment of burn injury by cellular repair

Burn injury leads to a direct damaging effect on cells, disrupting the assembly of the cell and denaturing proteins. Although modern medicine has significantly improved the survival of burn victims, a method to treat injury at the cellular level is presented. In particular, the cell membrane is most vulnerable to heat injury. Copolymer surfactants have been shown to repair the cell membrane, and agents such as poloxamer 188 have demonstrated this effect in numerous studies. Furthermore, copolymer surfactants have been shown to act as molecular chaperones, allowing denatured proteins to regain their native confirmation. Pharmaceutical agents may be developed to repair the cell membrane and refold proteins, mimicking endogenous repair mechanisms and salvaging cells that would otherwise be lost.

Neuroprotection from secondary injury by polyethylene glycol requires its internalization

Polyethylene glycol (PEG) is well known to both fuse and repair cell membranes. This capability has been exploited for such diverse usages as the construction of hybridomas and as a reparative agent following neurotrauma. The latter development has proceeded through preclinical testing in cases of naturally induced paraplegia in dogs. The mechanisms of action of polymer-mediated neurorepair/neuroprotection are still under investigation. It is likely that the unique interaction of hydrophilic polymers with the mechanical properties of cell membranes in concert with an ability to interfere with mechanisms of secondary injury such as the production of highly reactive oxygen species (ROS or `free radicals') is the basis for neuroprotection by polymers.

Here we provide further evidence that the ability of PEG to reduce or limit secondary injury and/or lipid peroxidation (LPO) of membranes requires entry of PEG into the cytosol, further suggesting a physical interaction with the membranes of organelles such as mitochondria as the initial event leading to neurorepair/neuroprotection.

We have evaluated this relationship in vitro using acrolein, a potent endogenous toxin that is a product of LPO. Acrolein can pass through cell membranes with ease, inducing progressive LPO in `bystander' cells, and the production of even more acrolein by inducing its own production. Immediate application of PEG (10 mmol l–1, 2000 Da) to poisoned neurons in vitro was unable to rescue them from necrosis and death. Furthermore, three-dimensional confocal microscopy of fluorescently decorated PEG shows that it does not enter these cells for up to 2 h after application. By this time the mechanisms of necrosis are likely irreversible. Additionally,severe oxygen and or glucose deprivation of spinal cord white matter in vitro also initiates LPO. Addition of potent free radical scavengers such as ascorbic acid or superoxide dismutase (SOD) is able to interfere with this process, but PEG is not. Taken together, these data are consistent with the hypothesis that PEG is able to rescue mechanically damaged cells, based on a restructuring of the damaged plasmalemma. Furthermore, in compromised cells with an intact cell membrane, PEG must first gain access to the cytosol where this same capability may be useful in restoring the integrity of cellular organelles such as mitochondria, though the intracellular concentration of the polymer must be significant relative to the concentration of toxins produced by LPO in order to rescue the cell.

Lipid Peroxidation Activates Mitogen-Activated Protein Kinases in Testicular Ischemia-Reperfusion Injury

PURPOSE

Testicular damage after torsion has been attributed to many mechanisms, of which one is lipid peroxidation of the plasma membrane, which could cause the activation of the mitogen-activated protein kinase family. These proteins are of vital importance for signal transduction pathways and 2 of them, extracellular signal-regulated kinase and c-jun N-terminal kinase, participate in the pathogenesis of testicular ischemia. We investigated whether lipid peroxidation may trigger mitogen-activated protein kinase activation in testicular ischemia-reperfusion.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats were subjected to 1-hour testicular ischemia, followed by 24 hours of reperfusion. Sham testicular ischemia-reperfusion rats served as controls. Animals were randomized to receive raxofelast, an inhibitor of lipid peroxidation (20 mg/kg intraperitoneally administered 15 minutes before detorsion and 15 minutes after detorsion) or vehicle (1 ml/kg 10% dimethyl sulfoxide/NaCl solution). A group of animals was sacrificed 0, 10, 15, 20, 25 and 30 minutes, and 1, 2 and 3 hours, respectively, after detorsion to evaluate testicular c-jun N-terminal kinase, extracellular signal-regulated kinase and tumor necrosis factor-alpha activation by Western blot analysis, and mRNA expression and conjugated dienes using a spectrophotometer technique. Another group was sacrificed 24 hours after detorsion to evaluate histological alterations.

RESULTS

Testicular ischemia-reperfusion injury caused a significant increase in the conjugated diene levels, extracellular signal-regulated kinase c-jun N-terminal kinase activity and tumor necrosis factor-alpha expression in both testes. Furthermore, histological examination revealed marked damage. Raxofelast inhibited these parameters and decreased histological damage.

CONCLUSIONS

These data suggest that lipid peroxidation triggers extracellular signal-regulated kinase and c-jun N-terminal kinase activation. Furthermore, mitogen-activated protein kinase blockade might represent a potential therapeutic approach to treatment in patients with unilateral testicular torsion.

Propofol attenuates reperfusion injury after testicular torsion and detorsion

Propofol, which is widely used as an intravenous anesthetic, has been shown to have an antioxidant activity on several tissues. This study was designed to investigate the prevention of reperfusion injury with propofol after testicular torsion. Five groups of rats (seven in each group) were used. Animals in the control group (group I) did not received any treatment, while animals in the sham group (group II) underwent scrotal incision and testicular fixation only. After 2 h of 720 degrees left testicular torsion in groups III, IV and V, subsequent detorsion was done for 2 h in groups IV and V. Propofol (50 mg/kg) was injected transperitoneally 30 min prior to detorsion in group V. Both testicles in all rats were retrieved and tissue malondialdeyhde (MDA) level, which is a measure of the amount of free oxygen radicals, and enzymatic activity of xanthine oxidase (XO), which converts hypoxanthine to xanthine and uric acid were studied. In addition, tissue catalase (CAT) and glutathione peroxidase (GSH-Px) activities, which are endogenous scavenger enzymes, protecting tissues against free radicals, were studied. Additionally, histological evaluations were performed after hematoxylin and eosin staining. Testicular MDA levels, and XO and CAT activities were higher in the torsion group compared to sham control group (P<0.05). Detorsion caused a further increase in MDA levels, contrasting with a decrease in the levels of XO activity, while CAT activity was not changed. Pretreatment with propofol prevented a further increase in MDA levels and significantly decreased CAT activity following detorsion. GSH-Px activities were not effected either by torsion/detorsion or propofol pretreatment. Histologically, torsion caused some separation between germinal cells in the seminiferous tubules, which became much more prominent in the detorsion group and attenuated with propofol pretreatment. There was no significant change in any of the above-mentioned enzymatic activities nor were there histopathological changes in the contralateral testicle in any groups. It is concluded that biochemically and histologically reperfusion injury occurs in the ipsilateral testis following detorsion up to 2 h. Preference of propofol for anaesthesia during the detorsion procedure may attenuate such reperfusion injury.

Poloxamer 188 prevents acute necrosis of adult skeletal muscle cells following high-dose irradiation

Acute cellular necrosis occurring minutes to hours after massive ionizing radiation exposure (IR) results from rapid membrane lipid peroxidation, blebbing and membrane breakdown. We have shown, previously, that certain polymer surfactants can restore structural integrity and transport barrier function of cell membranes following high-dose IR. We now investigate, specifically, the efficacy of the amphiphilic surfactant Poloxamer 188 (P188) in preventing acute necrosis of adult rat skeletal muscle cells after high-dose IR. Explanted cells were treated with 60Co IR doses of 10, 40 or 80Gy and their viability was determined using fluorometric probes at 4 and 18h post-IR. IR of 10Gy did not cause acute necrosis. Significant acute cell necrosis was observed after 40 and 80Gy doses in a dose-dependent manner. Post-IR treatment with P188 significantly enhanced the cells' viability post-IR treatment. By comparison 10kDa neutral dextran, a hydrophilic polymer, was found to be ineffective. Despite progressive cell death over 18h after high-dose IR, cells treated with P188 manifested greater survival than media or dextran-treated cells. It appears that use of P188 or similar multi-block copolymers to prolong viability of irradiated cells in vitro through membrane sealing is an important step in development of effective interventional therapy for extreme IR exposure. Not only can repairing the membrane prevent acute necrosis, but it also can provide a critical time opportunity to address other mechanisms of cell death, such as apoptosis or mitotic arrest, which manifest over a longer time frame.

Raxofelast, a hydrophilic vitamin E-like antioxidant, reduces testicular ischemia-reperfusion injury

Testis torsion is a surgical emergency that lead to permanent gonad damage. The damage has been ascribed to mechanisms of ischemia-reperfusion similar to other tissues. The mechanisms involved are different, but the lipid peroxidation of plasma membrane, caused by reactive oxygen species (ROS), generated particularly during reperfusion, is one of the most accredited. In the present study, we aimed to evaluate the effects of raxofelast, a vitamin E-like antioxidant with potent action and no systemic toxicity, on lipid peroxidation and histopathology in both testes after unilateral testicular torsion and detorsion. Adult male Wistar rats were subjected to total occlusion (3 h) of the left testis followed by 4 hours of reperfusion (TI/R). Sham testicular ischemia-reperfusion rats (SHAM TI/R) were used as controls. The animals were then randomized to receive either vehicle (1 ml/kg/i.p. of a dimetylsulphoxide/NaCl 0.9% 1:10 v/v solution, injected either 15 min before detorsion and 15 min after detorsion) or raxofelast (20 mg/kg i.p. 15 min before detorsion and 15 min after detorsion). Conjugated dienes (CD) levels, an index of lipid peroxidation, and testis histopathology were evaluated. Testicular ischemia reperfusion (TI/R) in untreated rats produced high testicular levels of CD (3.6+/-0.3 DeltaABS/g protein on the left side and 2.5+/-0.2 DeltaABS/g protein on the right side). Furthermore, histological examination revealed marked damage to the testis interstitium with severe haemorrhage and edema. The administration of raxofelast lowered CD levels (2.8+/-0.2 DeltaABS/g protein on the left side and 1.9+/-0.1 DeltaABS/g protein in the right side) and significantly reduced histological damage. These data suggest that the hydrophilic vitamin E-like antioxidants are good candidates for designing a novel therapeutic strategy to halt the oxidative stress that follows acute testis torsion.

Effect of insulin-like growth factor-1 on apoptosis of rat testicular germ cells induced by testicular torsion

OBJECTIVE

To investigate the possible protective role of insulin-like growth factor-1 (IGF-1, reported to have a protective effect in experimental models of hypoxic ischaemia), and the involvement of apoptotic cell death in a model of torsion/detorsion of the rat testis.

MATERIALS AND METHODS

Adult male Wistar rats were divided into five groups of five rats each. Group 1 underwent a sham operation as a control; in group 2 the testis was twisted and in group 3 then untwisted; in group 4 IGF-1 was injected subcutaneously just before bilateral torsion, and then the right testis removed after 4 h and the left after 24 h; in group 5, IGF-1 was injected immediately after bilateral detorsion and then the testes removed as in group 4. Both testicles were examined histologically, with apoptosis detected using the in situ DNA fragmentation (TUNEL) system, with combined enzymology and immunohistochemistry techniques.

RESULTS

In groups 2 (torsion) and 3 (detorsion), light microscopy of the testis showed some degenerative changes in the germ cells. Compared to group 1, apoptosis was more significant in group 3 than in the other groups. Group 4 (torsion/IGF-1) had a similar number of apoptotic germ cells as in group 2 (torsion) after 24 h, but fewer than the same group after 4 h. In group 5 (detorsion/IGF-1), apoptosis was reduced by IGF-1 significantly more than in group 3 (P < 0.05). Apoptosis was significantly less in spermatids in group 5 than in group 3 (P < 0.05).

CONCLUSIONS

IGF-1 seems to lower the levels of germ cell apoptosis, which may be important for protecting the testes from torsion/detorsion injury. Further clinical studies are needed to evaluate this protective effect in testicular torsion/detorsion.

Subcutaneous tri-block copolymer produces recovery from spinal cord injury

We have studied the ability of nonionic detergents and hydrophilic polymers to seal permeabilized membranes of damaged cells, rescuing them from progressive dissolution, degeneration, and death. We report that a single subcutaneous injection of the tri-block copolymer, Poloxamer 188 (P188) 6 hr after a severe compression of the adult guinea pig spinal cord is able to: (1). preserve the anatomic integrity of the cord; (2). produce a rapid recovery of nerve impulse conduction through the lesion; and (3). produce a behavioral recovery of a spinal cord dependent long tract spinal cord reflex. These observations stood out against a control group in blinded evaluation. Conduction through the lesion was monitored by stimulating the tibial nerve of the hind limb, and measuring the arrival of evoked potentials at the contralateral sensory cortex of the brain (somatosensory evoked potentials; SSEP). Behavioral recovery was determined by a return of sensitivity of formerly areflexic receptive fields of the cutaneous trunchi muscle (CTM) reflex. This contraction of back skin in response to tactile stimulation is totally dependent on the integrity of an identified bilateral column of ascending long tract axons. A statistically significant recovery of both SSEP conduction through the lesion and the CTM reflex occurred in P188-treated animals compared to vehicle-treated controls. Quantitative 3D computer reconstruction of the lesioned vertebral segment of spinal cord revealed a statistically significant sparing of spinal cord parenchyma and a significant reduction in cavitation of the spinal cord compared to control animals We determined that the proportion of P188-treated animals that recovered evoked potentials were nearly identical to that produced by a subcutaneous injection of polyethylene glycol (PEG). In contrast, P188 was not as effective as PEG in producing a recovery of CTM functioning. We discuss the likely differences in the mechanisms of action of these two polymers, and the possibilities inherent in a combined treatment.

The effect of poly (adenosine diphosphate-ribose) polymerase inhibitors on biochemical changes in testicular ischemia-reperfusion injury

PURPOSE

Poly (adenosine diphosphate [ADP]-ribose) polymerase inhibitors have been used successfully to decrease ischemia-reperfusion injury in several organ systems. We evaluated the efficacy of poly (ADP-ribose) polymerase inhibitors on biochemical changes in testicular ischemia-reperfusion injury.

MATERIALS AND METHODS

Adult male Wistar rats were divided into 9 groups of 6 each. One group served to determine baseline values of biochemical parameters, 1 that underwent sham operation served as a control, 1 underwent 2 hours of testicular torsion and 4 hours of detorsion, 2 received pretreatment with vehicle (saline or dimethyl sulfoxide) before detorsion and 4 received pretreatment with the poly (ADP-ribose) polymerase inhibitor nicotinamide, 3-aminobenzamide, 1,5-dihydroxyisoquinoline or 4-amino-1,8-naphthalimide before detorsion. Lipid peroxidation products, nitric oxide content and myeloperoxidase activity, an indicator of neutrophil accumulation, were assessed in testicular and renal tissues.

RESULTS

Testicular torsion-detorsion caused a significant increase in lipid peroxidation products, nitric oxide content and myeloperoxidase activity in ipsilateral testes (p <0.01) but not in the contralateral testes or kidneys. Animals treated with poly (ADP-ribose) polymerase inhibitors had a significant decrease in these biochemical parameters compared with vehicle treated animals (p <0.01).

CONCLUSIONS

These data emphasize that poly (ADP-ribose) polymerase may have a role in testicular damage caused by ischemia-reperfusion and the inhibition of poly (ADP-ribose) polymerase may be a novel approach to therapy for ischemia-reperfusion injury of the testis.

Synthesis and characterization of self-assembling block copolymers containing bioadhesive end groups

3,4-Dihydroxyphenyl-L-alanine (DOPA) is an unusual amino acid found in mussel adhesive proteins (MAPs) that is believed to lend adhesive characteristics to these proteins. In this paper, we describe a route for the conjugation of DOPA moieties to poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers. Hydroxyl end groups of PEO-PPO-PEO block copolymers were activated by N,N'-disuccinimidyl carbonate and then reacted with DOPA or its methyl ester with high coupling efficiencies from both aqueous and organic solvents. DOPA-modified PEO-PPO-PEO block copolymers were freely soluble in cold water, and dye partitioning and differential scanning calorimetry analysis of these solutions revealed that the copolymers aggregated into micelles at a characteristic temperature that was dependent on block copolymer composition and concentration in solution. Oscillatory rheometry demonstrated that above a block copolymer concentration of approximately 20 wt %, solutions of DOPA-modified PEO-PPO-PEO block copolymers exhibited sol-gel transitions upon heating. The gelation temperature could be tailored between approximately 23 and 46 degrees C by changing the composition, concentration, and molecular weight of the block copolymer. Rheological measurement of the bioadhesive interaction between DOPA-modified Pluronic and bovine submaxillary mucin indicated that DOPA-modified Pluronic was significantly more bioadhesive than unmodified Pluronic.

Polyethylene glycol rapidly restores physiological functions in damaged sciatic nerves of guinea pigs

OBJECTIVE

We have studied the ability of the hydrophilic polymer polyethylene glycol (PEG) to anatomically and physiologically reconnect damaged axons of the adult guinea pig spinal cord. Here we have extended this approach to test whether completely severed guinea pig sciatic nerves in isolation could be fused and whether PEG was able to repair severe standardized crush injuries to sciatic nerves in vivo.

METHODS

The fusion test was performed with isolated sciatic nerves maintained in a double-sucrose gap recording chamber. For in vivo experiments, the sciatic nerve was surgically exposed in the hind leg of deeply anesthetized adult guinea pigs and was crushed proximal to its insertion in the gastrocnemius muscle. PEG was injected just beneath the epineurium with a 29-gauge needle, allowed to remain in the damaged axon region for 2 minutes, and removed. Sham-treated guinea pigs received an injection of water or Krebs' solution. Three indices of recovery were simultaneously monitored in response to electrical stimulation of the proximal nerve, i.e., 1) recovery of compound muscle action potentials (in millivolts), 2) contraction force of the muscle (in dynes), and 3) displacement of the muscle (in millimeters).

RESULTS

When isolated sciatic nerves were severed within the double-sucrose gap chamber, compound action potential propagation through the transection plane was eliminated. After abutment of the two segments and 2-minute PEG application to this site, variable compound action potential recovery was measured in all four cases. The crush injuries to the sciatic nerve in vivo eliminated the three functional responses to sciatic nerve stimulation in all animals. Within the first 30 minutes after treatment, only 1 of 12 control animals exhibited spontaneous recovery in any of these measures, compared with six of eight PEG-treated animals. By 45 minutes, two more sham-treated animals and one more PEG-treated animal had recovered at least one functional response. This difference in proportions between PEG-treated and sham-treated animals was statistically significant (P < or =0.02).

CONCLUSION

We conclude that these preliminary data suggest that PEG application may be a way to interfere with the steady dissolution of peripheral nerve fibers after mechanical damage and to even functionally fuse or reconnect severed proximal and distal segments.

Behavioral recovery from spinal cord injury following delayed application of polyethylene glycol

Topical application of the hydrophilic polymer polyethylene glycol (PEG) to isolated adult guinea pig spinal cord injuries has been shown to lead to the recovery of both the anatomical integrity of the tissue and the conduction of nerve impulses through the lesion. Furthermore, a brief (2 min) application of the fusogen (Mr 1800, 50 % w/v aqueous solution) to the exposed spinal cord injury in vivo can also cause rapid recovery of nerve impulse conduction through the lesion in association with functional recovery. Behavioral recovery was demonstrated using a long-tract, spinal-cord-dependent behavior in rodents known as the cutaneus trunci muscle (CTM) reflex. This reflex is observed as a contraction of the skin of the back in response to tactile stimulation. Here, we confirm and extend these preliminary observations. A severe compression/contusion injury to the exposed thoracic spinal cord of the guinea pig was performed between thoracic vertebrae 10 and 11. Approximately 7 h later, a topical application of PEG was made to the injury (dura removed) for 2 min in 15 experimental animals, and levels of recovery were compared with those of 13 vehicle-treated control animals. In PEG-treated animals, 93 % recovered variable levels of CTM functioning and all recovered some level of conduction through the lesion, as measured by evoked potential techniques. The recovered reflex was relatively normal compared with the quantitative characteristics of the reflex prior to injury with respect to the direction, distance and velocity of skin contraction. Only 23 % of the control population showed any spontaneous CTM recovery (P=0.0003) and none recovered conduction through the lesion during the 1 month period of observation (P=0.0001). These results suggest that repair of nerve membranes by polymeric sealing can provide a novel means for the rapid restoration of function following spinal cord injury.

Rapid recovery from spinal cord injury after subcutaneously administered polyethylene glycol

Arguably a seminal event in most trauma and disease is the breakdown of the cell membrane. In most cells, this is first observed as a collapse of the axolemmas barrier properties allowing a derangement of ions to occur, leading to a progressive dissolution of the cell or its process. We have shown that an artificial sealing of mechanically damaged membranes by topical application of hydrophilic polymers such as polyethylene glycol (PEG) immediately restores variable levels of nerve impulse conduction through the lesion. This was documented by a rapid recovery of somatosensory evoked potential (SSEP) conduction, and by recovery of the cutaneous trunchi muscle (CTM) reflex in PEG-treated animals. The CTM reflex is a sensorimotor behavior dependent on an intact (and identified) white matter tract within the ventrolateral funiculus of the spinal cord, and is thus an excellent index of white matter integrity. We show that PEG can be safely introduced into the bloodstream by several routes of administration. Using a fluorescein decorated PEG, we demonstrate that the polymer specifically targets the hemorrhagic contusion of the adult guinea pig spinal cord when administered through the vasculature, but not intact regions of the spinal cord. A single subcutaneous injection (30% weight by weight in sterile saline) made 6 hr after a standardized spinal cord contusion in adult guinea pigs was sufficient to produce a rapid recovery of SSEP propagation through the lesion in only PEG-treated animals, accompanied by a statistically significant recovery of the CTM reflex. These data suggest that parenterally administered PEG may be a novel treatment for not only spinal injury, but head injury and stroke as well.

Cellular engineering: molecular repair of membranes to rescue cells of the damaged nervous system

PURPOSE

The acute administration of hydrophilic polymers (polyethylene glycol) can immediately seal nerve membranes, preventing their continuing dissolution and secondary axotomy. Polymer application can even be used to reconnect, or fuse, the proximal and distal segments of severed axons in completely transected adult mammalian spinal cord.

CONCEPT

The sealing or fusion of damaged nerve membranes leads to a very rapid (minutes or hours) recovery of excitability in severely damaged nerve fibers, observed as a rapid return of nerve impulse conduction in vitro, as well as an in vivo recovery of spinal cord conduction and behavioral loss in spinal cord-injured adult guinea pigs.

RATIONALE

Surfactant application produces a rapid repair of membrane breaches through mechanisms of interaction between the polymers and the aqueous phase of damaged membranes, and their ability to insert into, or seal, the hydrophobic core of the axolemma exposed by mechanical damage.

DISCUSSION

This new technology applied to severe neurotrauma offers a clinically safe and practical means to rescue significant populations of spinal cord nerve fibers within 8 hours after damage--preventing their continued dissolution and secondary axotomy by secondary injury mechanisms. Application of this novel technology to other injuries to the peripheral and central nervous system is discussed, as well as a general application to soft tissue trauma.

The effect of methylene blue on histological damage after spermatic cord torsion in a rat model

OBJECTIVE

To investigate, in a rat model, whether methylene blue (a free-radical scavenger) is effective in alleviating the histological testicular damage caused by reperfusion after spermatic cord torsion.

MATERIALS AND METHODS

Male Wistar rats underwent a clockwise 720 degrees left spermatic cord torsion lasting 3 h; they were then randomly assigned to treatment and control groups. In the treated group, 2 mg/kg methylene blue was injected intraperitoneally 20 min before the cord was untwisted, and an additional 1 mg/kg injected into the penile vein 1--2 min beforehand. After 14 days, the left testicle was removed and assessed histologically. The control group was not treated.

RESULTS

Thirty-three rats in the treatment group and 35 untreated controls were suitable for evaluation. Treatment with methylene blue was not significantly predictive of histological damage; the colour of the testis before detorsion was not correlated with histological damage.

CONCLUSION

Anti-oxidant treatment with methylene blue had no palliative effect on the histological changes after torsion and detorsion of the spermatic cord in this rat model.

Immediate recovery from spinal cord injury through molecular repair of nerve membranes with polyethylene glycol

A brief application of the hydrophilic polymer polyethylene glycol (PEG) swiftly repairs nerve membrane damage associated with severe spinal cord injury in adult guinea pigs. A 2 min application of PEG to a standardized compression injury to the cord immediately reversed the loss of nerve impulse conduction through the injury in all treated animals while nerve impulse conduction remained absent in all sham-treated guinea pigs. Physiological recovery was associated with a significant recovery of a quantifiable spinal cord dependent behavior in only PEG-treated animals. The application of PEG could be delayed for approximately 8 h without adversely affecting physiological and behavioral recovery which continued to improve for up to 1 month after PEG treatment.