The efficacy of eribulin mesylate for patients with cutaneous angiosarcoma previously treated with taxane: a multicentre prospective observational study.

BACKGROUND: Taxanes are the current first-line treatment for advanced cutaneous angiosarcoma (CAS) for patients who are considered difficult to treat with doxorubicin owing to advanced age or comorbidity. However, no effective second-line therapy for such patients has been established. METHODS: We designed a single-arm prospective observational study of eribulin mesylate (ERB) administered at a dose of 1·4 mg m-2 on days 1 and 8 in a 21-day cycle. Patients with advanced CAS who were previously treated with a taxane and were scheduled to begin ERB treatment were enrolled. The primary endpoint was overall survival (OS) and the secondary endpoints were response rate (RR), progression-free survival (PFS) and toxicity assessment. RESULTS: We enrolled a total of 25 patients. The median OS and PFS were 8·6 months and 3·0 months, respectively. The best overall RR was 20% (five of 25). In total, 16 grade 3/4 severe adverse events (SAEs) occurred; however, all patients recovered. Patients who achieved partial response or stable disease as best response had longer OS than those with progressive disease (median OS not reached and 3·3 months, respectively; P < 0·001). Patients who did not experience SAEs showed longer OS than those who did (median OS 18·8 months and 7·5 months, respectively; P < 0·05). Patients with distant metastasis had shorter median OS than those with locoregional disease, but without statistically significant difference. CONCLUSIONS: ERB showed a promising RR and is a potential candidate for second-line treatment for patients with CAS, after treatment with taxanes. However, owing to the occurrence of SAEs in over half of the participants, caution should be exercised regarding ERB use in elderly patients. What is already known about this topic? Taxanes are the current first-line treatment for patients with advanced cutaneous angiosarcoma (CAS) who are considered difficult to treat with doxorubicin owing to advanced age or comorbidity. No effective therapy for taxane-resistant CAS has been established thus far. Eribulin suppresses microtubule polymerization and elicits an antitumour effect similar to that of taxanes. What does this study add? In our single-arm prospective observational study to evaluate the efficacy of eribulin for treating patients with advanced CAS who previously received taxanes, the median overall survival and progression-free survival were 8·6 and 3·0 months, respectively. Response rates at weeks 7, 13 and 25 were 20%, 17% and 14%, respectively. Although 16 grade 3/4 severe adverse events occurred, all patients recovered. Eribulin showed a promising response rate and is a potential candidate for second-line treatment in CAS after taxane treatment. Linked Comment: Smrke and Benson. Br J Dermatol 2020; 183:797-798.

Three patients with advanced cutaneous angiosarcoma treated with eribulin: investigation of serum soluble CD163 and chemokine (C-X-C motif) ligand 10 as possible biomarkers predicting the biological behaviour of angiosarcoma.

Cutaneous angiosarcoma (CAS) is a highly aggressive vascular tumour that recurs locally and metastasizes early. Although chemoradiotherapy with taxanes shows a high response rate with prolonged survival, second-line therapy for advanced CAS remains contentious. This report describes three patients with advanced CAS treated with eribulin. In addition, we investigated serum soluble (s)CD163, chemokine (C-X-C motif) ligand 10 (CXCL10) and chemokine (C-C motif) ligand 2 levels at several time points of tumour progression in these patients, revealing serum levels of sCD163 and CXCL10 as potential biomarkers for progression of CAS.

Possible mechanisms of the crosstalk between Langerhans cells and regulatory T cells in extramammary Paget disease by receptor activator of nuclear factor kappa B (RANK) ligand/RANK pathways.

BACKGROUND: Extramammary Paget disease (EMPD) is a skin adenocarcinoma of apocrine gland origin, in which Paget cells express receptor activator of nuclear factor kappa B (RANK) ligand (RANKL) and matrix metalloproteinase (MMP)-7, and release soluble (s)RANKL into the tumour microenvironment. We previously reported that about 60% of the RANK+ cells among the stromal cells are M2 macrophages, but the identity of the remaining population of RANK+ cells is still unknown. OBJECTIVES: To investigate the unknown subpopulation of RANK-expressing cells in EMPD. METHODS: The main population of RANK-expressing cells in the epidermis was composed of epidermal Langerhans cells (LCs). To explore the effects of RANKL on LCs, we stimulated LCs generated from human CD34+ hematopoietic progenitor cells with graded concentrations of sRANKL. To further examine the correlation between LCs and regulatory T cells (Tregs) in EMPD, we employed immunohistochemical staining. RESULTS: sRANKL stimulation was shown to augment the production of C-C motif chemokine ligand 17 (CCL17) from LCs. We additionally demonstrated CCL17 expression by CD1a+ LCs in EMPD in an immunofluorescence study. Spearman's rank correlation test confirmed a correlation between the number of LCs and the number of Foxp3+ Tregs in the lesional skin of invasive EMPD. In addition, the numbers of Foxp3+ Tregs in the sentinel lymph nodes of metastatic EMPD were significantly higher than those of metastatic melanoma, which did not express RANKL. CONCLUSIONS: The findings suggest that the RANKL/RANK pathway in EMPD might contribute to the recruitment of Tregs and to maintenance of the tumour microenvironment.

High-Resolution C-Arm CT and Metal Artifact Reduction Software: A Novel Imaging Modality for Analyzing Aneurysms Treated with Stent-Assisted Coil Embolization.

BACKGROUND AND PURPOSE: Combination of high-resolution C-arm CT and novel metal artifact reduction software may contribute to the assessment of aneurysms treated with stent-assisted coil embolization. This study aimed to evaluate the efficacy of a novel Metal Artifact Reduction prototype software combined with the currently available high spatial-resolution C-arm CT prototype implementation by using an experimental aneurysm model treated with stent-assisted coil embolization. MATERIALS AND METHODS: Eight experimental aneurysms were created in 6 swine. Coil embolization of each aneurysm was performed by using a stent-assisted technique. High-resolution C-arm CT with intra-arterial contrast injection was performed immediately after the treatment. The obtained images were processed with Metal Artifact Reduction. Five neurointerventional specialists reviewed the image quality before and after Metal Artifact Reduction. Observational and quantitative analyses (via image analysis software) were performed. RESULTS: Every aneurysm was successfully created and treated with stent-assisted coil embolization. Before Metal Artifact Reduction, coil loops protruding through the stent lumen were not visualized due to the prominent metal artifacts produced by the coils. These became visible after Metal Artifact Reduction processing. Contrast filling in the residual aneurysm was also visualized after Metal Artifact Reduction in every aneurysm. Both the observational (P < .0001) and quantitative (P < .001) analyses showed significant reduction of the metal artifacts after application of the Metal Artifact Reduction prototype software. CONCLUSIONS: The combination of high-resolution C-arm CT and Metal Artifact Reduction enables differentiation of the coil mass, stent, and contrast material on the same image by significantly reducing the metal artifacts produced by the platinum coils. This novel image technique may improve the assessment of aneurysms treated with stent-assisted coil embolization.

Expression of CD39/Entpd1 on granuloma-composing cells and induction of Foxp3-positive regulatory T cells in sarcoidosis.

BACKGROUND: Regulatory T cells (Tregs), together with tolerogenic dendritic cells (tDCs) are involved in maintaining peripheral tolerance. A recent report suggested both Tregs and tDCs may be pathogenic in granulomatous skin disorders. AIM: To examined the expression of CD39 on granuloma-composing cells and Foxp3-positive Tregs in the skin in two representative granulomatous diseases, sarcoidosis and granuloma annulare (GA). METHODS: We immunohistologically examined expression of CD39 on granuloma-composing cells and expression of Foxp3 on CD4+ or CD25+ cells in fixed sections of lesional skin from 16 patients with sarcoidosis and five patients with GA. RESULTS: The granuloma-composing cells expressed CD39 in both sarcoidosis and GA. Significant numbers of CD4+ Foxp3+ Tregs were present diffusely throughout the granulomatous tissues in sarcoidosis, whereas Tregs in GA existed only at the peripheral lesion of palisading granulomatous tissue. CONCLUSIONS: There was infiltration of increased numbers of Foxp3+ Tregs around the CD39+ granuloma-composing cells in both GA and sarcoidosis.

Increased systemic inflammatory interleukin-1ß and interleukin-6 during agitation as predictors of Alzheimer's disease.

OBJECTS: Identification of biomarkers for Alzheimer's disease (AD) is important for its early diagnosis and prevention and a key in advancing our understanding of its pathophysiology. The aim of this study was to determine whether systemic inflammatory interleukin-1ß (IL-1ß) and interleukin-6 (IL-6) as well as hypertension (HT), diabetes mellitus (DM), and body mass index (BMI) are predictors of AD. METHODS: We performed a 10-year follow-up study on 133 elderly who were institutionalized in a nursing home. The associations of IL-1ß and IL-6 at both rest and agitation, as well as HT, DM, and BMI at baseline, were analyzed with the incidences of vascular dementia (VD) and AD during a 10-year follow-up period. RESULTS: The Kaplan-Meier method with log-rank test and Cox regression analyses for the total of 133 subjects showed significantly higher incidences of both VD and AD in subjects with DM or HT at baseline. Resting IL-1ß or IL-6 value, or agitation score, was not significantly associated with the subsequent development of VD or AD. The analyses of 40 subjects who had shown agitation at least once in the previous 3 months demonstrated that IL-1ß and IL-6 values at the agitation stage were significantly associated with AD, but not with VD. CONCLUSION: Our results indicate that systemic inflammatory IL-1ß and IL-6 at the agitation stage are risk factors for the development of AD, but not VD. Inflammatory mechanisms for AD seem to be causal and specific to the development of AD.

Association between altered systemic inflammatory interleukin-1beta and natural killer cell activity and subsequently agitation in patients with Alzheimer disease.

OBJECTIVE: Alzheimer's disease (AD) is a neurodegenerative disorder that is the most common cause of dementia in the elderly and is frequently accompanied by emotional disorder, including agitation. Although evidence of neuroendocrine immune and inflammatory functions during emotional changes has been accumulated, the pathogenic mechanisms in the development of agitation accompanied by AD remain to be elucidated. METHODS: To clarify the involvement of neuroendocrine and immune and inflammatory systems in agitation in AD, we examined agitation levels, circadian rhythms of behavior, cortisol, interleukin-1beta (IL-1beta), and natural killer cell activity (NKCA) in controls without dementia and 16 AD patients who were recognized to be easily agitated in their nursing homes. These behavioral and blood indicators were assessed according to the progress of the stage of agitation in 16 AD patients (stable, pre-agitation, and agitation stages). RESULTS: Elevations in night behavior and blood cortisol, IL-1beta and an reduced blood NKCA level in the evening were observed not only in the agitation stage, but also when stable in AD patients as compared to the control. Increased IL-1beta and decreased NKCA occurred in both the morning and evening in pre-agitation and agitation stages in AD. CONCLUSIONS: The increased IL-1beta and decreased NKCA with the progress of agitation in AD suggest that inflammation produces agitation and aggravates AD.

Safety, tolerability and pharmacokinetics of oral S-3304, a novel matrix metalloproteinase inhibitor, in single and multiple dose escalation studies in healthy volunteers.

OBJECTIVE: A novel sulfonamide derivative, S-3304, was discovered as a potent matrix metalloproteinase (MMP) inhibitor. It is a more specific inhibitor to MMP-2 and MMP-9 (in vitro) than to MMP-1, and may therefore lack the musculoskeletal side effects seen with non-specific inhibitors. The aim of the present study was to investigate the safety, tolerability and pharmacokinetics of S-3304 when administered as single and multiple oral doses to healthy male volunteers. MATERIALS AND METHODS: 48 male volunteers received single oral doses ranging from 10 - 800 mg S-3304 or placebo under fasting conditions. At the 200 mg dose level, effects of high-fat diets were studied in a crossover design. In the multiple dose design, 24 male subjects were administered 200 mg, 400 mg or 800 mg S-3304 or placebo b.i.d. after meals for 10 - 17 days. Studies were conducted in a randomized double-blind fashion. Safety assessment was conducted based on blood chemistry, hematology, urinalysis, electrocardiogram and physical examination. Pharmacokinetic parameters were determined for S-3304 and its metabolites. All subjects were enrolled in the studies after obtaining informed consent. RESULTS: Adverse events reported after single dose administration of S-3304 or placebo were all of mild severity. Adverse events reported in the multiple dose treatment with S-3304 or placebo were mostly of mild severity, except for two episodes of moderate headache and two episodes of moderate myalgia. Most commonly reported adverse events in the multiple treatments with S-3304 were headache and somnolence. No clinically significant changes were observed in the clinical laboratory tests, except for reversible elevation of alanine aminotransferase of one subject at 800 mg S-3304 b.i.d. In the single dose administration, Cmax and mean AUC0-infinity linearly increased up to 63,167 ng/ml and 311,960 ng x h/ml at the 800 mg dose level, respectively; tmax and t1/2 ranged from 2 - 3 hours and from 9.5 - 15.5 hours, respectively. High-fat diets reduced Cmax from 21,565 ng/ml to 14,095 ng/ml but did not alter AUC0-infinity. Hydroxylated metabolites were detected in plasma in concentrations less than 1% of S-3304. Less than 1% S-3304 was excreted in urine. The AUC of one dosing interval and Cmax did not change after multiple doses but t1/2 increased from 9.5 - 10.0 hours to 12.5 - 13.5 hours. The 6beta-hydroxycortisol/ cortisol ratio was not changed after multiple doses suggesting no effect on CYP3A4 activity. CONCLUSION: S-3304 demonstrated a good safety profile and good systemic exposure when administered orally up to 800 mg b.i.d. during 10 - 17 days. At the highest dose level of 800 mg b.i.d., it was free of rheumatoid arthritis-like symptoms.

Blood endothelin-1 and cold-induced vasodilation in patients with primary Raynauld's phenomenon and workers with vibration-induced white finger.

AIM: Cold water-immersion induces vasoconstriction with an elevation of blood endothelin-1, which is a potent vasoconstrictor peptide, in patients with primary Raynaud's phenomenon (PRP). However, physiological involvement of endothelin-1 in cold-induced vasodilation (CIVD) remains to be elucidated. METHODS: We monitored changes of finger blood flow during cold water (10 degrees C) immersion and assayed blood endothelin-1 in 7 PRP patients and 7 workers with vibration-induced white finger (VWF) and in the respective control subjects. RESULTS: While significant reductions in finger blood flow at 2 min after the immersion were observed in PRP patients and VWF workers, its elevation at 4 min, which was considered to reflect CIVD, was recognized only in PRP patients. In healthy controls, blood endothelin-1 increased at 4 min and returned to the basal level immediately after the immersion. The increase in blood endothelin-1 at 4 min in PRP patients was greater than that in controls, and continued even after the immersion. Conversely, the increase neither at 4 min nor after immersion was seen in VWF workers. Local vascular changes produced by repetitive vibration may be responsible for the attenuated CIVD and unchanged blood endothelin-1 during cold water-immersion in VWF workers. CONCLUSION: Our results showing elevated blood endothelin-1 during and after immersion in PRP contrast with that in VWF suggesting that endothelin-1 is related to sympathetic hyperactivity which is more involved in PRP rather than VWF. It seems unlikely that endothelin-1 is functionally or directly associated with CIVD.

Phospholipase C-dependent hydrolysis of phosphatidylcholine hydroperoxides to diacylglycerol hydroperoxides and its reduction by phospholipid hydroperoxide glutathione peroxidase.

We have shown that 1,2-diacylglycerol hydroperoxides activate protein kinase C (PKC) as efficiently as does phorbol ester [Takekoshi S, Kambayashi Y, Nagata H, Takagi T, Yamamoto Y, Watanabe K. Activation of protein kinase C by oxidized diacylglycerol. Biochem Biophys Res Commun 1995; 217: 654-660]. 1,2-Diacylglycerol hydroperoxides also stimulate human neutrophils to release superoxide whereas their hydroxides do not [Yamamoto Y, Kambayashi Y, Ito T, Watanabe K, Nakano M. 1,2-Diacylglycerol hydroperoxides induce the generation and release of superoxide anion from human polymorphonuclear leukocytes. FEBS Lett 1997; 412: 461-464]. One of the proposed mechanisms for the formation of 1,2-diacylglycerol hydroperoxides is the hydrolysis of phosphatidylcholine hydroperoxides by phospholipase C (PLC). To confirm this hypothesis, we incubated 1-palmitoyl-2-linoleoyl-phosphatidylcholine (PLPC) liposomes containing PLPC hydroperoxides (PLPC-OOH) with Bacillus cereus PLC and found 1-palmitoyl-2-linoleoylglycerol (PLG) and its hydroperoxide (PLG-OOH) were produced. PLC hydrolyzed the two substrates without preference, as the yields of PLG and PLG-OOH were the same even though cholesterol was incorporated into liposomes to increase bilayer integrity. Phospholipid hydroperoxide glutathione peroxidase (PHGPX) reduced PLG-OOH to its hydroxide in the presence of glutathione while the conventional cytosolic glutathione peroxidase did not. These data suggest that PLC hydrolyzes oxidized biomembranes to give 1,2-diacylglycerol hydroperoxides for PKC stimulation but PHGPX may prevent neutrophil stimulation by reducing 1,2-diacylglycerol hydroperoxides to their hydroxides.

Gas6 rescues cortical neurons from amyloid beta protein-induced apoptosis.

Gas6, a product of the growth-arrest-specific gene 6, protects neurons from serum deprivation-induced apoptosis. Neuronal apoptosis is also caused by amyloid beta protein (Abeta), whose accumulation in the brain is a characteristic feature of Alzheimer's disease. Abeta induces Ca(2+) influx via L-type voltage-dependent calcium channels (L-VSCCs), leading to its neurotoxicity. In the present study, we investigated effects of Gas6 on Abeta-induced cell death in primary cultures of rat cortical neurons. Abeta caused neuronal cell death in a concentration- and time-dependent manner. Gas6 significantly prevented neurons from Abeta-induced cell death. Gas6 ameliorated Abeta-induced apoptotic features such as the condensation of chromatin and the fragmentation of DNA. Prior to cell death, Abeta increased influx of Ca(2+) into neurons through L-VSCCs. Gas6 significantly inhibited the Abeta-induced Ca(2+) influx. The inhibitor of L-VSCCs also suppressed Abeta-induced neuronal cell death. The present cortical cultures contained few non-neuronal cells, indicating that Gas6 affected the survival of neurons directly, but not indirectly via non-neuronal cells. In conclusion, we demonstrate that Gas6 rescues cortical neurons from Abeta-induced apoptosis. Furthermore, the present study indicates that inhibition of L-VSCC contributes to the neuroprotective effect of Gas6.

Effects of S-2474, a novel nonsteroidal anti-inflammatory drug, on amyloid beta protein-induced neuronal cell death.

1. The accumulation of amyloid beta protein (Abeta) in the brain is a characteristic feature of Alzheimer's disease (AD). Clinical trials of AD patients with nonsteroidal anti-inflammatory drugs (NSAIDs) indicate a clinical benefit. NSAIDs are presumed to act by suppressing inhibiting chronic inflammation in the brain of AD patients. 2. In the present study, we investigated effects of S-2474 on Abeta-induced cell death in primary cultures of rat cortical neurons. 3. S-2474 is a novel NSAID, which inhibits cyclo-oxygenase-2 (COX-2) and contains the di-tert-butylphenol antioxidant moiety. S-2474 significantly prevented neurons from Abeta(25 - 35)- and Abeta(1 - 40)-induced cell death. S-2474 ameliorated Abeta-induced apoptotic features such as the condensation of chromatin and the fragmentation of DNA completely. 4. Prior to cell death, Abeta(25 - 35) generated prostaglandin D(2) (PGD(2)) and free radicals from neurons. PGD(2) is a product of cyclo-oxygenase (COX), and caused neuronal cell death. 5. S-2474 significantly inhibited the Abeta(25 - 35)-induced generation of PGD(2) and free radicals. 6. The present cortical cultures contained little non-neuronal cells, indicating that S-2474 affected neuronal survival directly, but not indirectly via non-neuronal cells. Both an inhibitory effect of COX-2 and an antioxidant effect might contribute to the neuroprotective effects of S-2474. 7. In conclusion, S-2474 exhibits protective effects against neurotoxicity of Abeta. Furthermore, the present study suggests that S-2474 may possess therapeutic potential for AD via ameliorating degeneration in neurons as well as suppressing chronic inflammation in non-neuronal cells.

Characteristics of chemiluminescence observed in the horseradish peroxidase-hydrogen peroxide-tyrosine system.

Electrolysis or horseradish peroxidase (HRP)-catalyzed oxidation of tyrosine and bityrosine in aqueous solution at pH 7.4 resulted in light emission in the visible region. Electrolysis of tyrosine emitted light which peaked at 490 nm and was almost completely quenched by superoxide dismutase (SOD), while emission by bityrosine peaked at 530 nm. In the HRP-H(2)O(2)-tyrosine system the oxidation-reduction of tyrosine emitted light with two prominent peaks, 490 and 530 nm, and was not quenched by SOD. The phenoxyl neutral radical of the tyrosine in HRP-H(2)O(2)-tyrosine system was detected by electron spin resonance (ESR) spectrometry using tert-nitrosobutane as a spin trap; the spin adduct was found to adhere to the HRP molecule during the enzymatic reaction. Further, bityrosine was detected in the HRP-H(2)O(2)-tyrosine reaction system. Changes in absorption spectra of HRP and chemiluminescence intensities during HRP-catalyzed oxidation of tyrosine suggest that for photon emission compound III is a candidate superoxide donor to the phenoxyl cation radical of tyrosine on the enzyme molecule. The luminescence observed in this study might be originated from at least two exciplexes involved with the tyrosine cation radical (Tyr(*+)) and the bityrosine cation radical (BT(*+))

Angiotensin receptors: molecular biology and signalling.

1. The active peptide hormone angiotensin II (AngII) is formed from its prohormone angiotensinogen by way of inactive angiotensin I. The highly specific protease, renin, responsible for the initiation of this system was elusive and considered unstable. We isolated it in a pure and stable form from the kidney of the pig, human, rat, and land submandibular glands of the mouse. It was shown that there is only one type of renin with highly stringent substrate specificity, except certain strains of the mouse which have two gene products. 2. The well-known diversity of action of AngII can be attributed to the presence of more than two subtypes, AT1 and AT2, as well as multiple signalling pathways for both of them. 3. The first subtype AT1 was shown to mediate most of the traditionally recognized AngII functions such as vasoconstriction, electrolyte homeostasis etc. 4. Although the identification of the signalling modes of the second subtype AT2 still remains elusive, we and others have shown evidence that its action is generally antagonistic to that of AT1. AT2 inhibits AT1 (growth factor-stimulated cell growth), AT2 attenuates the vasoconstriction induced by AT1. Since AT2 seems to mediate nitric oxide formation in the renal cells, it may initiate a natriuretic pathway in contrast to the sodium-retaining action of AT1-mediated AngII action. 5. Newer mechanisms and functions of these and other receptors will be clarified by the combination of molecular, cellular and integrated physiological studies.

Correlation of antiangiogenic and antitumor efficacy of N-biphenyl sulfonyl-phenylalanine hydroxiamic acid (BPHA), an orally-active, selective matrix metalloproteinase inhibitor.

The antiangiogenic activity and antitumor efficacy of a newly developed matrix metalloproteinase (MMP) inhibitor were examined. N-biphenyl sulfonyl-phenylalanine hydroxiamic acid (BPHA) potently inhibits MMP-2, -9, and -14, but not MMP-1, -3, or -7. In contrast, (-)BPHA, an enantiomer of BPHA, was inactive against all MMPs tested. Daily oral administration of 200 mg/kg BPHA, but not (-)BPHA in mice resulted in potent inhibition of tumor-induced angiogenesis, primary tumor growth, and liver metastasis. The growth inhibition activity of BPHA was 48% and 45% in a B16-BL6 melanoma and F2 hemangio-endothelioma model, respectively. BPHA also showed 42% inhibition of the liver metastasis of C-1H human colon carcinoma cells. These results indicate that selective MMP inhibition is correlated with antiangiogenic and antitumor efficacy and that the selective MMP inhibitor BPHA has therapeutic potential.

Inactivation of bacterial respiratory chain enzymes by singlet oxygen.

To distinguish the bactericidal action of singlet oxygen (1O2) from hypohalous acids, wild-type and lycopene transformant E. coli strains were exposed to each of the oxidants and then bacterial viability was investigated. 1O2 was generated by chemical and enzymatic systems at pH 4.5. ExpoSure of wild-type E. coli to 1O2 caused a significant loss of E. coli viability due to inactivation of membrane respiratory chain enzymes by 1O2. This action of 1O2 could be attenuated by lycopene in the bacterial cell membrane. In the lycopene transformant strain of E. coli, inactivation of NADH oxidase and succinate oxidase by hypohalous acids were significantly suppressed, but E. coli viability was unaffected. Based on these findings, we suggest that phagocytic leukocytes produce 1O2 as a major bactericidal oxidant in the phagosome.

Useful 1O2 (1delta g) generator, 3-(4'-methyl-1'-naphthyl)-propionic acid, 1',4'-endoperoxide (NEPO), for dioxygenation of squalence (a skin surface lipid) in an organic solvent and bacterial killing in aqueous medium.

3-(4'-Methyl-1'-naphthyl)-propionic acid, 1',4'-endoperoxide (NEPO) provides singlet state of oxygen (1O2, 1delta g) at 37 degrees C in sodium phosphate buffer (pH 7.2), acetate buffer (pH 4.5), methanol or chloroform, through the retro-Diels-Alder reaction. The total amount of 1O2 generated by NEPO was calculated using the following equation: [1O2]= [NEPO]0[1-exp(-kt)], where [1O2], [NEPO]0 and k are the total amount of 1O2 produced during the time t, initial concentration of NEPO and the first-order reaction rate constant, respectively. When squalene was exposed to 1O2 which was generated thermolytically from NEPO, it was oxidized to three hydroperoxides, mono-, di- and tri-hydroperoxides, in amounts proportional to the dose of NEPO. The oxidizability of squalene was much more extensive compared with unsaturated phospholipids. Additionally, when wild-type E. coli and lycopene-producing mutant E. coli were exposed to NEPO-derived 1O2, there was significant loss of viability of wild-type E. coli but no significant loss of viability in lycopene-producing strain, suggesting that lycopene by scavenging 1O2 protected E. coli against 1O2 toxicity.