The Effects of Lipopolysaccharide Derivatives in Rodent Models of Cardiac Arrhythmia

BACKGROUND

Several previous studies have suggested that sublethal doses of Escherichia coli lipopolysaccharide (endotoxin) and monophosphoryl lipid A Re595, a nonpyrogenic derivative of Salmonella minnesota lipopolysaccharide, exhibit antiarrhythmic effects in the rat model of ischemia-reperfusion arrhythmias.

METHODS

In this study, the protective effect of lipopolysaccharide derivatives was also further investigated in drug (aconitine or ouabain)-induced arrhythmia models, and conclusions were drawn with particular emphasis on the molecular characteristics of different types of lipopolysaccharide.

RESULTS

The importance of the molecular structure for the antiarrhythmic effect of monophosphoryl lipid A and E. coli lipopolysaccharide was tested in the ischemia-reperfusion arrhythmia model. In contrast to monophosphoryl lipid A from Salmonella typhimurium SL 684 which has only monophosphoryl residue in its structure, monophosphoryl lipid A Re595, obtained from S. minnesota, and E. coli lipopolysaccharide which have both mono and diphosphoryl residue reduced the duration of ventricular tachycardia (e.g., during reperfusion: vehicle: 176 ± 22.8; monophosphoryl lipid A Re595: 132.83 ± 12.1, as second, n=8-10, P < .05) and the incidence of ventricular fibrillation. The antiarrhythmic effects of E. coli lipopolysaccharide and monophosphoryl lipid A Re595 in ischemia-reperfusion arrhythmia model were absent in either aconitine- (e.g., onset time for ventricular ectopic beats: saline 25.3 5.0, E. coli lipopolysaccharide 24.3 ± 7.1; vehicle: 24.0 ± 4.5, monophosphoryl lipid A SL684 23.8 ± 4.3, as second, n=6, P > .05) or ouabain-induced arrhythmia models in mice.

CONCLUSION

Therefore, we conclude that lipopolysaccharide derivatives exhibit antiarrhythmic effect only in ischemia-reperfusion arrhythmias, and lipopolysaccharide should possess diphosphoryl groups in its subcomponent composition for this antiarrhythmic effect.

MicroCrystalline Tyrosine-adsorbed immunotherapy

PURPOSE OF REVIEW

The purpose of this article is to provide an overview of the literature pertaining to the use of MicroCrystalline Tyrosine (MCT) in the immunotherapy with an emphasis on recent developments.

RECENT FINDINGS

In addition to significant effectiveness and safety profiles, additional aspects of interest such as booster immunotherapy concepts, sustained clinical effects, long-term efficacy and disease-modifying effects are being focused on in the recently published studies. The depot adjuvant MCT also shows potential in promising disease-challenge models such as for malaria and melanoma.

SUMMARY

MCT-adsorbed immunotherapy products have been shown to provide convincing overall safety, tolerability and efficacy outcomes, as well in vulnerable groups such as children and asthmatic patients.

A vaccine against methamphetamine attenuates its behavioral effects in mice

BACKGROUND

Vaccines have treatment potential for methamphetamine (MA) addiction. We tested whether a conjugate vaccine against MA (succinyl-methamphetamine-keyhole limpet hemocyanin carrier protein; SMA-KLH) would generate MA antibodies and alter MA-induced behaviors.

METHODS

Mice were injected with SMA-KLH and received booster administrations 3 and 20 weeks later. Serum antibody titers reached peak levels by 4-6 weeks, remained at a modest level through 18 weeks, peaked again at 22 weeks after the second boost, and were still elevated at 35 weeks. At 7 weeks, groups of vaccinated and non-vaccinated mice were administered one of three MA doses (1, 2 or 3 mg/kg) to assess locomotor activity.

RESULTS

Non-vaccinated mice showed dose-dependent effects of MA with hypolocomotion at the lowest dose and elevated activity levels at the highest dose. Both dose effects were reduced in SMA-KLH groups, particularly low dose-induced hypolocomotion at later times post MA administration. Separate groups of vaccinated and non-vaccinated mice were trained in MA place conditioning at 30 weeks with either 0 (vehicle) or 0.5mg/kg MA. Although times spent in the MA-paired side did not differ between groups on test vs. baseline sessions, SMA-KLH mice conditioned with MA showed reduced conditioned approach behaviors and decreased conditioned activity levels compared to control groups.

CONCLUSION

These data suggest SMA-KLH attenuates the ability of MA to support place conditioning and reduces or delays its locomotor effects. Overall, results support SMA-KLH as a candidate MA vaccine.

Synthesis of a monophosphoryl derivative of Escherichia coli lipid A and its efficient coupling to a tumor-associated carbohydrate antigen

Monophosphoryl lipid A is a safe and potent immunostimulant and vaccine adjuvant, which is potentially useful for the development of effective carbohydrate-based conjugate vaccines. This paper presents a convergent and efficient synthesis of a monophosphoryl derivative of E. coli lipid A that has an alkyne functionality at the reducing end, which is suitable for coupling with various molecules. The coupling of this derivative to an N-modified analogue of tumor-associated antigen GM3 through click chemistry is also presented.

Chemical synthesis and proinflammatory responses of monophosphoryl lipid A adjuvant candidates

Lipopolysaccharides (LPS), which are structural components of the outer surface membrane of Gram-negative bacteria, trigger innate immune responses through activation of Toll-like receptor 4 (TLR4). Such responses may be exploited for the development of adjuvants and in particular monophosphoryl lipid A (MPLA) obtained by controlled hydrolysis of LPS of Salmonella minnesota, exhibits low toxicity yet possesses beneficial immuno-stimulatory properties. We have developed an efficient synthetic approach for the preparation of a major component of MPLA (1), which has as a key feature the use of allyloxycarbonates (Alloc) as permanent protecting groups for the C-3 and C-4 hydroxyls of the proximal glucosamine unit. The latter protecting groups greatly facilitated deprotection of the fully assembled compound. Furthermore, the amino functions were protected as N-2,2,2-trichloroethoxycarbamates (Troc), which performed efficient neighboring group participation to give selectively 1,2-trans-glycosides and could easily be removed under mild conditions without affecting the permanent Alloc carbonates and anomeric dimethylthexylsilyl (TDS) ether. The synthetic methodology was also employed for the preparation of a monophosphoryl lipid A (2) derivative that has the anomeric center of the proximal sugar modified as a methyl glycoside. Compound 1 was not able to induce cytokine production in mouse macrophages whereas methyl glycoside 2 displayed activity, however it has a lower potency and efficacy than lipid A obtained by controlled hydrolysis S. minnesota. This indicates compound 2 is an attractive candidate for adjuvant development and that 1 is not the active substance of MPLA obtained by controlled hydrolysis of LPS.

Triggering role of nitric oxide in the delayed protective effect of monophosphoryl lipid A in rat heart

1. The main objective of the present study was to further evaluate the role of nitric oxide (NO) in delayed cardiac protection against ischaemia-reperfusion injury induced by monophosphoryl lipid A (MLA). 2. For this purpose, rats were administered with either 0.5 or 2.5 mg kg(-1) MLA (i.p.). Eight or 24 h later, in vivo NO production in the heart was analysed by electron paramagnetic resonance (EPR) spin trapping technique. In parallel experiments, hearts were removed and perfused according to Langendorff. Functional ventricular parameters and incidence of ventricular fibrillation (VF) were determined after 30 min global ischaemic insult (37 degrees C) followed by 30 min reperfusion. Vascular reactivity of aortic rings was also assessed. 3. Hearts from rats pretreated with 2.5 mg kg(-1) MLA for 24 h (but not those from rats treated with 0.5 mg kg(-1) MLA for 8 and 24 h, or with 2.5 mg kg(-1) MLA for 8 h) exhibited preservation of ventricular function (LVDP, +/-dP/dtmax) and a reduced incidence of VF (25% vs 87.5% in vehicle control) during reperfusion. At the cardioprotective dose of 2.5 mg kg(-1) (for 8 or 24 h), MLA did not produce alterations of the contractile response of aortic rings to noradrenaline. 4. An increased formation of NO was detected in hearts removed from rats pretreated with 2.5 mg kg(-1) MLA for 8 h, but not in those from rats treated for 24 h (or with 0.5 mg kg(-1) MLA). 5. Pretreatment of the animals with the inhibitors of inducible NO-synthase, aminoguanidine (2x300 mg kg(-1)) or L-N6-(1-Iminoethyl)-lysine (L-NIL, 10 mg kg(-1)) abolished both MLA (2. 5 mg kg(-1))-induced rise of NO production (observed 8 h after MLA) and cardioprotection (observed 24 h after MLA). However MLA-induced cardioprotection was not attenuated when the hearts were perfused with aminoguanidine (150 microM) for 30 min before the ischaemic insult. 6. Altogether, the present data suggest that NO acts as a trigger rather then a direct mediator of the delayed cardioprotective effect of MLA in rat heart.