New lipoic acid derivative drug sodium zinc dihydrolipoylhistidinate prevents cardiac dysfunction in an isolated perfused rat heart model*:

An α-Lipoic acid derivative, and anti-ROS agent, prevents the acquisition of multi-drug resistance in clinical isolates of Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the most common causes of nosocomial infections, and its multi-drug resistance has been a serious problem worldwide. The aim of this study was to evaluate whether exposure to piperacillin and reactive oxygen species (ROS) could lead to multi-drug resistance for clinical isolates of P. aeruginosa. The inhibition of this acquired resistance by the anti-ROS agent was also examined. In vitro inducement of multi-drug resistance was performed against 20 clinical isolates. These strains were incubated for 24 h and transferred 5 times after being exposed to 1 mM H₂O₂ (ROS) in addition to a sub-MIC of piperacillin by the agar dilution method. Each MIC of piperacillin and levofloxacin was determined. As the mechanism of levofloxacin resistance, mutation of QRDR was investigated. The expression level of genes encoding efflux pumps; mexA, mexY, mexC, and D2 porin; oprD were determined by real-time PCR. Multi-resistance to both piperacillin and levofloxacin was induced with 4 of 20 strains (20%). No amino acid change was confirmed in QRDR. These strains showed overexpression of mexA, mexY, mexC, and another one showed decrease of oprD expression. Resistance development in 4 strains was inhibited by the same method including the anti-ROS agent, sodium zinc histidine dithiooctanamide (DHL-His-Zn). In conclusion, stimulation by ROS promoted acquisition of multi-drug resistance in 20% of isolates of P. aeruginosa, and DHL-His-Zn completely inhibited this acquisition of resistance. Therefore, this anti-ROS agent may be useful to assist antimicrobial chemotherapy by preventing multi-drug resistance.

Neuropathic pain attenuates ischemia reperfusion injury through β2-adrenergic pathway

AIMS

The relationship between neuropathic pain and myocardial infarction (MI) was uncertain because of some medication or underlying diseases. This study investigated the impact of neuropathic pain on ischemia reperfusion injury using isolated rat hearts and cardiomyocytes.

MAIN METHODS

Male Sprague-Dawley rats were assigned to the control and allodynia (AL) groups, with the latter subjected to the fifth lumbar spinal-nerve ligation. First, isolated hearts underwent 25-min ischemia and 90-min reperfusion to assess hemodynamic changes and MI area. Second, isolated cardiomyocytes underwent 10-min laser illumination to assess the opening of mitochondrial permeability transition pore (mPTP) and cellular hypercontraction. Lastly, expression of pro-survival kinases was measured in another cardiomyocytes using flow cytometry. AL-treated hearts were concomitantly examined regarding the involvement of β-adrenergic pathways by esmolol (ESM), β1-blocker (100μM, AL+ESM), and ICI118551 (ICI), β2-blocker (50nM, AL+ICI).

KEY FINDINGS

All hemodynamic variables did not change significantly in between-group comparisons except at 30min of reperfusion. MI area decreased remarkably in the AL and AL+ESM groups after 90-min reperfusion. The AL+ICI group significantly increased it as compared with the AL and AL+ESM groups. Similarly, the AL and AL+ESM groups significantly inhibited mPTP opening and cellular hypercontraction, whereas the AL+ICI group reversed these effects. Enhanced expression of pro-survival kinases was observed in the AL and AL+ESM groups, but the AL+ICI group abolished this enhancement.

SIGNIFICANCE

Our findings suggested that neuropathic pain possessed cardioprotective effects through inhibiting mPTP opening. The underlying mechanisms were possibly regulated by β2-adrenergic activation and pro-survival kinase expression in cardiomyocytes.

The alpha-lipoic acid derivative DHLHZn: a new therapeutic agent for acute lung injury in vivo

OBJECTIVE AND DESIGN

An animal experiment was performed to demonstrate the anti-inflammatory effects of an alpha-lipoic acid (ALA) derivative, dihydrolipoyl histidinate zinc complex (DHLHZn) for acute lung injury (ALI) and to investigate the mechanism of action.

MATERIAL

Rats were randomly divided into three experimental groups: control group (n = 17), DHLHZn(-) group (n = 11, ALI model rats), and DHLHZn(+) group (n = 12, ALI model rats treated by DHLHZn).

TREATMENT

Lipopolysaccharides (LPS, 10 mg/kg) were administered intratracheally in the DHLHZn(-) group and the DHLHZn(+) group. For the DHLHZn(+) group, DHLHZn (100 mg/kg) was administered intraperitoneally 2 h prior to LPS administration.

METHODS

Four hours after LPS administration, bronchoalveolar lavage fluid (BALF) and lung tissue were collected. The findings were analyzed using the Mann-Whitney U test.

RESULTS

Total number of cells, number of neutrophils and lymphocytes, levels of various inflammatory cytokines, and NF-kB p65 concentration of BALF were significantly lower in the DHLHZn(+) group than in the DHLHZn(-) group (p < 0.05). ALI pathology scores were significantly lower in the DHLHZn(+) group than in the DHLHZn(-) group (p < 0.001).

CONCLUSIONS

Anti-inflammatory effects of DHLHZn for ALI were demonstrated by BALF and histopathological findings. The mechanism of action of DHLHZn was considered to be via inhibition of the NF-kB signaling pathway. DHLHZn is thus suggested to be a new prophylactic agent for ALI.

Establishment of a model of atrial fibrillation associated with chronic kidney disease in rats and the role of oxidative stress

BACKGROUND

An animal model of atrial fibrillation (AF) associated with chronic kidney disease (CKD) has not been available.

OBJECTIVE

The purpose of this study was to test the validity of 5/6 nephrectomy (5.6Nx) as an appropriate model of AF associated with CKD and to investigate the role of oxidative stress.

METHODS

Male Sprague-Dawley rats were subjected to 5.6Nx. A novel derivative of lipoic acid, sodium zinc dihydrolipoylhistidinate (DHLHZn), was subcutaneously infused. Four weeks later, hearts were isolated.

RESULTS

We observed 5 main findings. (1) 5.6Nx induced renal dysfunction with elevation of systolic blood pressure and impaired glucose tolerance. (2) In the left atrium (LA), expressions of α-smooth muscle action and collagen type I, the compositional proteins of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, and malondialdehyde were increased by 5.6Nx, which was reversed by DHLHZn treatment. (3) In the LA, the tissue content of angiotensin II was elevated by 5.6Nx, which was also reversed by DHLHZn. (4) Masson trichrome staining revealed that heterogeneous LA interstitial fibrosis was induced by 5.6Nx, which was attenuated by DHLHZn. (5) In isolated perfused heart experiments, 5.6Nx caused slowing of interatrial conduction. In the hearts of rats of the 5.6Nxgroup, right atrial extrastimuli invariably induced AF (8/8 [100%]), which were suppressed by DHLHZn (3/8 [38%], P <.05).

CONCLUSION

We successfully established an appropriate model of AF associated with CKD in rats. Because the amount of NADPH oxidase was increased and the potent antioxidant agent DHLHZn was effective, oxidative stress may be involved in the pathogenesis of LA fibrosis and enhanced AF vulnerability in our model.

Cardioprotective effect of total paeony glycosides against isoprenaline-induced myocardial ischemia in rats

Paeoniae radix is a traditional Chinese medicinal herb for treating some diseases; important components are total paeony glycosides (TPGs), an approved drug by the State Food and Drug Administration (SFDA) for the therapy of rheumatoid arthritis (RA). We firstly reported myocardial benefits of TPGs previously, and the present study is to further investigate the underlying mechanisms for preventing oxidative damage in cardiomyopathy. We measured the capacity of TPGs to scavenge free radicals in vitro. Then 60 SD rats were randomly divided into five groups: (1) a normal control group, (2) an isoprenaline (ISO)-induced myocardial ischemic model group, (3) a TPG treatment group (TPGs 269.4 mg/kg delivered by intragastric administration for 3 days before ISO administration and TPGs 449 mg/kg delivered for 3 days after ISO administration), (4) a TPG therapy group (TPGs 449 mg/kg delivered for 3 days after ISO administration), and (5) a positive control group (propranolol 15 mg/kg for 3 days after ISO administration). The ISO-induced myocardial ischemic model was established by subcutaneous injection of 1mg/kg/8h ISO (2 times). The activities of myocardial enzymes, including glutamic oxaloacetic transaminase (GOT), creatine kinase (CK), lactate dehydrogenase (LDH), antioxidant enzyme superoxide dismutase (SOD) as well as the content of lipid peroxidation product malondialdehyde (MDA) were detected. We found that TPGs potently eliminated hydroxyl radicals and superoxide in vitro using ESR assays. Compared with model rats, TPG treatment, TPG therapy and the positive control treatment exhibited significantly reduced activities of GOT, LDH, and CK (p < 0.01), increased activity of SOD (p < 0.01) and lower levels of MDA (p < 0.05). More interestingly, the protective effect of TPG treatment was even better than that of propranolol. These results suggest that TPGs significantly ameliorate ISO-induced myocardial ischemia and their action might be through reducing oxidative stress in ischemic myocardium.