Protective role of γ-aminobutyric acid against chronic renal failure in rats

The renoprotective activity of amikacin-gamma-amino butyric acid-chitosan nanoparticles: a comparative study

The development of nanoparticles (NPs) with active components with upgraded stability, and prolonged release helps in enhanced tissue regeneration. In addition, NPs are feasible strategy to boost antibiotic effectiveness and reduce drug side effects. Our study focuses on the use of amikacin (AMK) and gamma amino butyric acid (GABA) unloaded combinations or loaded on chitosan nanoparticles (CSNPs) for kidney protection. The AMK-GABA-CSNPs were prepared with the ionic gelation method, the morphology was studied using transmission electron microscopy (TEM), zetasizer and the Fourier transform-infrared spectroscopy (FT-IR) spectrum of the synthesized NPs was observed. The average size of AMK-GABA-CSNPs was 77.5 ± 16.5 nm. Zeta potential was + 38.94 ± 2.65 mV. AMK-GABA-CSNPs revealed significant in vitro antioxidant, anti-coagulation, non-hemolytic properties and good cell compatibility. To compare the effects of the unloaded AMK-GABA combination and AMK-GABA-CSNPs on the renal tissue, 42 healthy Sprague-Dawley rats were divided into seven groups. G1: normal control (NC), normal saline; G2: low-dose nephrotoxic group (LDN), AMK (20 mg/kg/day; i.p.); G3: unloaded AMK (20 mg/kg/day; i.p.) and GABA (50 mg/kg/day; i.p.); G4: AMK-GABA-CSNPs (20 mg/kg/day; i.p.); G5: high-dose nephrotoxic group (HDN), AMK (30 mg/kg/day; i.p.); G6: unloaded AMK (30 mg/kg/day; i.p.) and GABA (50 mg/kg/day; i.p.) and G7: AMK-GABA-CSNPs (30 mg/kg/day; i.p.). The results showed that AMK-GABA-CSNPs formulation is superior to unloaded AMK-GABA combination as it ameliorated kidney functions, oxidative stress and displayed a significant homeostatic role via suppression of inflammatory cytokines of Th1, Th2 and Th17 types. Hence, AMK-GABA-CSNPs could afford a potential nano-based therapeutic formula for the management of AMK-nephrotoxicity.

The Aging GABAergic System and Its Nutritional Support

Aging is associated with a decline in hormones and an associated decline in GABAergic function and calcium and ion current dysregulation. Neurosteroid hormones act as direct calcium channel blockers, or they can act indirectly on calcium channels through their interaction with GABA receptors. The calcium channel dysfunction associated with hormone loss further leads to an excitatory cell state, which can ultimately lead to cell death. The calcium theory of aging posits that cellular mechanisms, which maintain the homeostasis of cytosol Ca2+ concentration, play a key role in brain aging and that sustained changes in Ca2+ homeostasis provide the final common pathway for age-associated brain changes. There is a link between hormone loss and calcium dysregulation. Loss of calcium regulation associated with aging can lead to an excitatory cell state, primarily in the mitochondria and nerve cells, which can ultimately lead to cell death if not kept in check. A decline in GABAergic function can also be specifically tied to declines in progesterone, allopregnanolone, and DHEA levels associated with aging. This decline in GABAergic function associated with hormone loss ultimately affects GABAergic inhibition or excitement and calcium regulation throughout the body. In addition, declines in GABAergic function can also be tied to vitamin status and to toxic chemicals in the food supply. The decline in GABAergic function associated with aging has an effect on just about every body organ system. Nutritional support of the GABAergic system with supportive foods, vitamins, and GABA or similar GABA receptor ligands may address some of the GABAergic dysfunction associated with aging.

γ-Aminobutyric acid found in fermented foods and beverages: current trends

γ-aminobutyric acid (GABA) is synthesised by glutamic acid decarboxylase which catalyses the decarboxylation of L-glutamic acid. L-glutamic acid is formed by α-ketoglutarate in the TCA cycle by glutamic acid dehydrogenase (GDH). GABA is found in the human brain, plants, animals and microorganisms. GABA functions as an antidepressant, antihypertensive, antidiabetic and immune system enhancer and has a good effect on neural disease. As GABA have pharmaceutical properties, conditions for GABA production need to be established. Microbiological GABA production is more safe and eco-friendly rather than chemical methods. Moreover, it is easier to control conditions of production using microorganisms compared to production in plants and animals. GABA production in fermented foods and beverages has the potential to be optimised to increase the functional effect of fermented foods and beverages.

Effects of gamma-aminobutyric acid and piperine on gene regulation in pig kidney epithelial cell lines

Objective

Gamma-aminobutyric acid (GABA) and piperine (PIP) are both nutritional supplements with potential use in animal diets. The purpose of this study is to investigate the effect of GABA and/or PIP treatment on the gene expression pattern of a pig kidney epithelial cell line.

Methods

LLCPK1 cells were treated with GABA, PIP, or both, and then the gene expression pattern was analyzed using microarray. Gene ontology analysis was done using GeneOntology (Geneontology.org), and validation was performed using quantitative real-time polymerase chain reaction.

Results

Gene ontology enrichment analysis was used to identify key pathway(s) of genes whose expression levels were regulated by these treatments. Microarray results showed that GABA had a positive effect on the transcription of genes related to regulation of erythrocyte differentiation and that GABA and PIP in combination had a synergistic effect on genes related to immune systems and processes. Furthermore, we found that effects of GABA and/or PIP on these selected genes were controlled by JNK/p38 MAPK pathway.

Conclusion

These results can improve our understanding of mechanisms involved in the effect of GABA and/or PIP treatment on pig kidney epithelial cells. They can also help us evaluate their potential as a clinical diagnosis and treatment.

A novel sympathetic neuronal GABAergic signalling system regulates NE release to prevent ventricular arrhythmias after acute myocardial infarction

AIM

Overactivation of the sympathetic nerve may lead to severe ventricular arrhythmias (VAs) after myocardial infarction (MI). Thus, targeting sympathetic nerve activity is an effective strategy to prevent VAs clinically. The superior cervical ganglion (SCG), the extracardiac sympathetic ganglion innervating cardiac muscles, has been found to have a GABAergic signalling system, the physiological significance of which is obscure. We aimed to explore the functional significance of SCG post MI and whether the GABAergic signal system is involved in the process.

METHODS

Adult male Sprague-Dawley rats were divided into seven different groups. Rats in the MI groups underwent ligation of the left anterior descending coronary artery. All animals were used for electrophysiological testing, renal sympathetic nerve activity (RSNA) testing, and ELISA. Primary SCG sympathetic neurons were used for the in vitro study.

RESULTS

The GABA_A receptor agonist muscimol significantly decreased the ATP-induced increase in intracellular Ca²⁺ (P < 0.05). GABA treatment in MI rats significantly attenuated the level of serum and cardiac norepinephrine (NE; P < 0.05). Sympathetic activity and inducible VAs were also lower in MI + GABA rats than in MI rats (P < 0.05). Knockdown of the GABA_A Rs β₂ subunit (GABA_A Rβ₂ ) in the SCG of MI rats increased the NE levels in serum and cardiac tissue, RSNA and inducible VAs compared with vehicle shRNA (P < 0.05).

CONCLUSION

The GABAergic signalling system is functionally expressed in SCG sympathetic neurons, and activation of this system suppresses sympathetic activity, thereby facilitating cardiac protection and making it a potential target to alleviate VAs.

An Updated Review on Pharmaceutical Properties of Gamma-Aminobutyric Acid

Gamma-aminobutyric acid (Gaba) is a non-proteinogenic amino acid that is widely present in microorganisms, plants, and vertebrates. So far, Gaba is well known as a main inhibitory neurotransmitter in the central nervous system. Its physiological roles are related to the modulation of synaptic transmission, the promotion of neuronal development and relaxation, and the prevention of sleeplessness and depression. Besides, various pharmaceutical properties of Gaba on non-neuronal peripheral tissues and organs were also reported due to anti-hypertension, anti-diabetes, anti-cancer, antioxidant, anti-inflammation, anti-microbial, anti-allergy, hepato-protection, reno-protection, and intestinal protection. Therefore, Gaba may be considered as potential alternative therapeutics for prevention and treatment of various diseases. Accordingly, this updated review was mainly focused to describe the pharmaceutical properties of Gaba as well as emphasize its important role regarding human health.

Combined effect of GABA and glucagon-like peptide-1 receptor agonist on cytokine-induced apoptosis in pancreatic β-cell line and isolated human islets

BACKGROUND

Treatment with GABA or glucagon-like peptide-1 (GLP-1) can preserve pancreatic β-cell mass and prevent diabetes. Recently, we reported that the combination of GABA and sitagliptin (a dipeptidyl peptidase-4 inhibitor that increases endogenous GLP-1) was more effective than either agent alone in reducing drug-induced β-cell damage and promoting β-cell regeneration in mice. However, in human islets, it remains unclear whether GABA and GLP-1 exert similar effects.

METHODS

To investigate GABA and GLP-1 interactions, human islets or INS-1 cells were treated with GABA and/or exendin-4, a GLP-1 receptor agonist (GLP-1RA) in clinical use, and incubated with a cytokine mixture for 24 hours. Cleaved caspase-3 and annexin V binding were measured by western blot and flow cytometry analysis, respectively, to investigate effects on cytokine-induced apoptosis.

RESULTS

Cytokine-induced apoptosis was reduced by either GABA or exendin-4 alone. This was markedly improved by combining GABA and exendin-4, resulting in a reversal of apoptosis. The combination notably increased Akt pathway signaling. Furthermore, sirtuin-1 (SIRT1) and α-Klotho, both reported to have protective effects on β-cells, were increased. Importantly, the combination ameliorated insulin secretion by human β-cells.

CONCLUSIONS

The combination of GABA and a GLP-1RA exerted additive effects on β-cell survival and function, suggesting that this combination may be superior to either drug alone in the treatment of diabetes.

Chemical-nutritional quality and oxidative stability of milk and dairy products obtained from Friesian cows fed with a dietary supplementation of dried grape pomace

BACKGROUND

The aim of the study was to evaluate the nutritional properties of milk and cheese obtained from Friesian cows fed with a diet supplemented with dried grape pomace, a by-product of the oenological industry, which is very rich in polyphenols. This approach is inspired by the increasing interest in foods containing functional ingredients that may have beneficial effects on human health. During the testing period, analyses of the chemical and nutritional properties of milk and dairy products derived from it were performed; particular attention was given to the effect of cheese ripening on the oxidative stability and fermentation process, evaluating respectively the presence of malondialdehyde and γ-aminobutyric acid.

RESULTS

Dietary enrichment with grape pomace did not affect the milk composition but induced modifications in the fatty acid profiles in both milk and cheese with an increase in concentration of linoleic acid, trans-vaccenic acid, rumenic acid and total n-6 fatty acids. Moreover, after 30 days of cheese ripening, an increased oxidative stability and an increased concentration of γ-aminobutyric acid were found.

CONCLUSIONS

Our results indicated a general improvement in nutritional parameters of milk and related cheese obtained from Friesian cows that received the feeding enrichment with dried grape pomace. Further analysis should be performed to improve knowledge of the chemical and microbiological mechanisms at the source of these findings. © 2019 Society of Chemical Industry.

Effects of a nutraceutical combination of monacolin, γ-oryzanol and γ-aminobutyric acid on lipid profile and C-reactive protein in mice

INTRODUCTION

The aim of this study was to evaluate the efficacy of two nutraceutical agents aimed to improve lipid profile in a sample of mice.

MATERIAL AND METHODS

Fifty mice were randomly divided into four groups. Control mice were fed a standard diet (SD), while the other three groups were fed with a high-fat diet (HFD) for 4 weeks. At the end of the run-in period, mice fed with the SD continued to follow the SD, while mice fed with the HFD were divided into three groups: one continued with the HFD, one continued to follow the HFD + a blend of natural components derived from rice and fermented rice (monacolin K 3%, γ-oryzanol, and γ-aminobutyric acid) (S1), and the other one followed the HFD + one nutraceutical containing monacolin K 3% alone for 24 weeks.

RESULTS

The results showed that mice treated with HFD + S1 and HFD + S2 had lower levels of TC compared to mice fed with the HFD alone (p < 0.01, and p < 0.05, respectively). Moreover, mice treated with HFD + S1 had lower TC and LDL-C levels compared to mice fed with HFD + S2 (p < 0.05). Mice treated with HFD + S1 or S2 had lower Tg levels compared to mice fed with the HFD (p < 0.05).

CONCLUSIONS

We can conclude that a combination of monacolin K 3%, γ-oryzanol, and γ-aminobutyric acid is more effective than monacolin K 3% alone in reducing the negative effects of a HFD in a sample of specific pathogen-free mice.

Induction of functional erythropoietin and erythropoietin receptor gene expression by gamma-aminobutyric acid and piperine in kidney epithelial cells

AIMS

The aim of this study was to evaluate gamma-aminobutyric acid (GABA)- and piperine-induced erythropoietin (EPO) and EPO-receptor expression.

MATERIALS AND METHODS

The effect of GABA and piperine on cell viability was examined using kidney epithelial cells. Expression levels of EPO and EPO-R mRNA and protein were evaluated in response to GABA and piperine treatments. GABA- and piperine-mediated activation of the mitogen-activated protein kinase (MAPK) signaling pathway was investigated. Additionally, EPO function was evaluated using conditioned media containing EPO. The GABA receptor type involved in this process was identified.

KEY FINDINGS

Messenger RNA and protein expression levels of EPO and EPO-R significantly increased in response to treatment with GABA, piperine, or the combination of both, compared with control. GABA plus piperine synergistically enhanced EPO and EPO-R expression through p38 and c-Jun N-terminal kinase (JNK) MAPK signaling pathways, but not through the extracellular signal-regulated kinase (ERK) MAPK pathway. SB203580 and SP600125 (p38 and JNK pathway inhibitors, respectively) attenuated GABA plus piperine-induced EPO and EPO-R expression. Treatment of macrophages with EPO-containing conditioned media induced mRNA expression of interleukin (IL)-10 and nuclear factor (NF)-κB due to the interaction between EPO and EPO-R. Interestingly, GABA-induced EPO and EPO-R expression was mediated through GABA_A, not GABA_B, receptor activation.

SIGNIFICANCE

These findings demonstrate that GABA plus piperine-mediated p38 and JNK MAPK activation increases EPO and EPO-R expression, resulting in up-regulation of IL-10 and NF-κB.

Boldine Improves Kidney Damage in the Goldblatt 2K1C Model Avoiding the Increase in TGF-β

Boldine, a major aporphine alkaloid found in the Chilean boldo tree, is a potent antioxidant. Oxidative stress plays a detrimental role in the pathogenesis of kidney damage in renovascular hypertension (RVH). The activation of the renin-angiotensin system (RAS) is crucial to the development and progression of hypertensive renal damage and TGF-β is closely associated with the activation of RAS. In the present study, we assessed the effect of boldine on the progression of kidney disease using the 2K1C hypertension model and identifying mediators in the RAS, such as TGF-β, that could be modulated by this alkaloid. Toward this hypothesis, rats (n = 5/group) were treated with boldine (50 mg/kg/day, gavage) for six weeks after 2K1C surgery (pressure ≥ 180 mmHg). Kidney function was evaluated by measuring of proteinuria/creatininuria ratio (U prot/U Crea), oxidative stress (OS) by measuring thiobarbituric acid reactive substances (TBARS). The evolution of systolic blood pressure (SBP) was followed weekly. Alpha-smooth muscle actin (α-SMA) and Col III were used as markers of kidney damage; ED-1 and osteopontin (OPN) were used as markers of inflammation. We also explored the effect in RAS mediators, such as ACE-1 and TGF-β. Boldine treatment reduced the UProt/UCrea ratio, plasma TBARS, and slightly reduced SBP in 2K1C hypertensive rats, producing no effect in control animals. In 2K1C rats treated with boldine the levels of α-SMA, Col III, ED-1, and OPN were lower when compared to 2K1C rats. Boldine prevented the increase in ACE-1 and TGF-β in 2K1C rats, suggesting that boldine reduces kidney damage. These results suggest that boldine could potentially be used as a nutraceutic.

Molecular Characterization of GABA-A Receptor Subunit Diversity within Major Peripheral Organs and Their Plasticity in Response to Early Life Psychosocial Stress

Gamma aminobutyric acid (GABA) subtype A receptors (GABA_ARs) are integral membrane ion channels composed of five individual proteins or subunits. Up to 19 different GABA_AR subunits (α1–6, β1–3, γ1–3, δ, ε, θ, π, and ρ1–3) have been identified, resulting in anatomically, physiologically, and pharmacologically distinct multiple receptor subtypes, and therefore GABA-mediated inhibition, across the central nervous system (CNS). Additionally, GABA_AR-modulating drugs are important tools in clinical medicine, although their use is limited by adverse effects. While significant advances have been made in terms of characterizing the GABA_AR system within the brain, relatively less is known about the molecular phenotypes within the peripheral nervous system of major organ systems. This represents a potentially missed therapeutic opportunity in terms of utilizing or repurposing clinically available GABA_AR drugs, as well as promising research compounds discarded due to their poor CNS penetrance, for the treatment of peripheral disorders. In addition, a broader understanding of the peripheral GABA_AR subtype repertoires will contribute to the design of therapies which minimize peripheral side-effects when treating CNS disorders. We have recently provided a high resolution molecular and function characterization of the GABA_ARs within the enteric nervous system of the mouse colon. In this study, the aim was to determine the constituent GABA_AR subunit expression profiles of the mouse bladder, heart, liver, kidney, lung, and stomach, using reverse transcription polymerase chain reaction and western blotting with brain as control. The data indicate that while some subunits are expressed widely across various organs (α3–5), others are restricted to individual organs (γ2, only stomach). Furthermore, we demonstrate complex organ-specific developmental expression plasticity of the transporters which determine the chloride gradient within cells, and therefore whether GABA_AR activation has a depolarizing or hyperpolarizing effect. Finally, we demonstrate that prior exposure to early life psychosocial stress induces significant changes in peripheral GABA_AR subunit expression and chloride transporters, in an organ- and subunit-specific manner. Collectively, the data demonstrate the molecular diversity of the peripheral GABA_AR system and how this changes dynamically in response to life experience. This provides a molecular platform for functional analyses of the GABA–GABA_AR system in health, and in diseases affecting various peripheral organs.

The Role of Gamma Amino Butyric Acid in Cisplatin-induced Nephrotoxicity in Streptozotocin-induced Diabetic Rats

Background:

Diabetes mellitus can change the risk of developing cancer. Cisplatin (CP) is a common antineoplastic drug. The major side effect of CP is nephrotoxicity. Gamma amino butyric acid (GABA) is an antioxidant agent that may have a protective role against CP-induced nephrotoxicity. The aim of the present study was to investigate the role of GABA in CP-induced nephrotoxicity in hyperglycemic male and female rats.

Materials and Methods:

Sixty male and female Wistar diabetic rats were used in ten experimental groups. GABA alone groups received GABA (50 μmol/kg/d i.p.) for 12 days. CP alone groups received CP (2.5 mg/kg/d i.p.) for 6 days. Other groups received GABA in the form of therapy (T) + CP, prophylaxis (P) + CP, and prophylaxis-treatment (PT) + CP. Finally, blood samples were obtained, and animals were killed for kidney tissue investigation.

Results:

In female rats, the serum levels of creatinine (Cr) did not change by GABA rather than CP and also there were no significant changes in blood urea nitrogen to creatinine ratio (BUN/Cr). In male rats, plasma Cr level increased by GABA (P) and (T). Body weight loss was significantly different among groups (P < 0.05). BUN/Cr ratio significantly increased in CP and GABA (PT) + CP groups. In two genders, plasma Cr level significantly decreased in CP groups (P < 0.05). The kidney levels of malondialdehyde enhanced significantly in CP groups.

Conclusion:

Hyperglycemia has protective effect against CP-induced nephrotoxicity. GABA did not change this effect in female, but in male in the form of PT, GABA maintained it.

Gamma Amino Butyric Acid Attenuates Brain Oxidative Damage Associated with Insulin Alteration in Streptozotocin-Treated Rats

The aim of the current study was to evaluate the role of γ-amino butyric acid (GABA) in insulin disturbance and hyperglycemia associated with brain oxidative damage in streptozotocin-treated rats. Streptozotocin (STZ) was administered to male albino rats as a single intraperitoneal dose (60 mg/kg body weight). GABA (200 mg/Kg body weight/day) was administered daily via gavages during 3 weeks to STZ-treated-rats. Male albino rats Sprague-Dawley (10 ± 2 weeks old; 120 ± 10 g body weight) were divided into 4 groups of 6 rats and treated in parallel. (1) Control group: received distilled water, (2) GABA group: received GABA, (3) STZ group: STZ-treated rats received distilled water, (4) STZ + GABA group: STZ-treated rats received GABA. Rats were sacrificed after a fasting period of 12 h next last dose of GABA. The results obtained showed that STZ-treatment produced hyperglycemia and insulin deficiency (similar to type1 Diabetes). These changes were associated with oxidative damage in brain tissue and notified by significant decreases of superoxide dismutase and catalase activities in parallel to significant increases of malondialdehyde and advanced oxidation protein products levels. The histopathology reports also revealed that STZ-treatment produced degeneration of pancreatic cells. The administration of GABA to STZ-treated rats preserved pancreatic tissue with improved insulin secretion, improved glucose level and minimized oxidative stress in brain tissues. It could be concluded that GABA might protect the brain from oxidative stress and preserve pancreas tissues with adjusting glucose and insulin levels in Diabetic rats and might decrease the risk of neurodegenerative disease in diabetes.

Effect of Γ-aminobutyric acid on kidney injury induced by renal ischemia-reperfusion in male and female rats: Gender-related difference

Background:

The most important cause of kidney injury is renal ischemia/reperfusion injury (IRI), which is gender-related. This study was designed to investigate the protective role of Γ-aminobutyric acid (GABA (against IRI in male and female rats.

Materials and Methods:

Thirty-six female and male wistar rats were assigned to six experimental groups. The IRI was induced by clamping renal vessels for 45 min then was performed reperfusion for 24 h. The group sex posed to IRI were pretreated with GABA and were compared with the control groups.

Results:

Serum levels of creatinine and blood urea nitrogen, kidney weight, and kidney tissue damage score increased in the IRI alone groups, (P < 0.05), while GABA decreased these parameters in female significantly (P < 0.05), but not in male rats. Uterus weight decreased significantly in female rats treated with GABA. Testis weight did not alter in male rats. Serum level of nitrite and kidney level of malondialdehyde (MDA) had no significant change in both female and male rats. Kidney level of nitrite increased significantly in female rats experienced IRI and serum level of MDA increased significantly in males that were exposed to IRI (P < 0.05).

Conclusion:

GABA could ameliorate kidney injury induced by renal IRI in a gender dependent manner.

Beneficial effects of γ-aminobutyric acid on right ventricular pressure and pulmonary vascular remodeling in experimental pulmonary hypertension

AIMS

It has been reported that activation of the sympathetic nervous system and increase in plasma norepinephrine (NE) levels are observed in patients with pulmonary hypertension (PH). γ-Aminobutyric acid (GABA) is one of the major inhibitory neurotransmitters in the central nervous system and suppresses peripheral sympathetic neurotransmission. This study investigated whether chronic treatment with GABA prevents the development of monocrotaline (MCT)-induced PH. To elucidate the relationship between the development of PH and sympathetic nerve activity, hemodynamic parameters, cardiac functions, and plasma NE concentrations as well as cardiac endothelin-1 (ET-1) contents of MCT-induced PH rats were evaluated with or without GABA treatment.

MAIN METHODS

Rats were injected with MCT (60 mg/kg) or saline subcutaneously and these rats were randomly divided into GABA (500 mg/kg/day for 4 weeks)- or vehicle-treated groups, respectively.

KEY FINDING

MCT-treated rats had higher right ventricular systolic pressures, right ventricle-to-left ventricle plus septum weight ratios, pulmonary arterial medial thickening, and plasma NE levels than those of saline-injected rats. MCT-induced alternations were significantly attenuated by treatment with GABA. In MCT-induced PH rats with or without GABA treatment, plasma NE levels were positively correlated with right ventricular systolic pressure. Right ventricular endothelin-1 (ET-1) contents were increased by MCT injection, but these increments were not affected by treatment with GABA.

SIGNIFICANCE

These results suggest that plasma NE levels play an important role in the development of MCT-induced PH in rats and that GABA exerts a preventive effect against MCT-induced PH by suppressing the sympathetic nervous system but not the cardiac ET-1 system.

Zinc ion enhances GABA tea-mediated oxidative DNA damage

GABA tea is a tea product that contains a high level of γ-aminobutyric acid (GABA). Previous study has demonstrated a synergistic effect of GABA tea and copper ions on DNA breakage. This study further explored whether zinc (Zn), a nonredox metal, modulated DNA cleavage induced by GABA tea extract. In a cell-free system, Zn(2+) significantly enhanced GABA tea extract and (-)-epigallocatechin-3-gallate (EGCG)- or H(2)O(2)-induced DNA damage at 24 h of incubation. Additionally, low dosages of GABA tea extract (1-10 μg/mL) possessed pro-oxidant activity to increase H(2)O(2)/Zn(2+)-induced DNA cleavage in a dose-dependent profile. By use of various reactive oxygen scavengers, it was observed that glutathione, catalase, and potassium iodide effectively inhibited DNA degradation caused by the GABA tea extract/H(2)O(2)/Zn(2+) system. Moreover, the data showed that the GABA tea extract itself (0.5-5 mg/mL) could induce DNA cleavage in a long-term exposure (48 h). EGCG, but not the GABA tea extract, enhanced H(2)O(2)-induced DNA cleavage. In contrast, GABA decreased H(2)O(2)- and EGCG-induced DNA cleavage, suggesting that GABA might contribute the major effect on the antioxidant activity of GABA tea extract. Furthermore, a comet assay revealed that GABA tea extract (0.25 mg/mL) and GABA had antioxidant activity on H(2)O(2)-induced DNA breakage in human peripheral lymphocytes. Taken together, these findings indicate that GABA tea has the potential of both pro-oxidant and antioxidant. It is proposed that a balance between EGCG-induced pro-oxidation and GABA-mediated antioxidation may occur in a complex mixture of GABA tea extract.

Renoprotective effects of gamma-aminobutyric acid on ischemia/reperfusion-induced renal injury in rats

Enhanced renal sympathetic nerve activity during ischemic period and the renal venous norepinephrine overflow after reperfusion play important roles in the development of ischemic acute kidney injury. We investigated the effect of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter mainly in the central nervous system, on ischemia/reperfusion-induced acute kidney injury in anesthetized rats. Ischemic acute kidney injury was induced by clamping the left renal artery and vein for 45min followed by reperfusion 2weeks after the contralateral nephrectomy. Intravenous injection of GABA (10 and 50micromol/kg) to ischemic acute kidney injury rats dose-dependently suppressed the enhanced renal sympathetic nerve activity during the renal ischemia, the renal venous norepinephrine overflow after reperfusion and attenuated the ischemia/reperfusion-induced renal dysfunction with histological damage. Intravenous injection of CGP52432 (0.1micromol/kg), a selective GABA(B) receptor antagonist, eliminated the preventive effect by GABA (50micromol/kg) on ischemic acute kidney injury. In contrast, intravenous injection of baclofen (1micromol/kg), a selective GABA(B) receptor agonist, attenuated the ischemia/reperfusion-induced renal injury equivalent to GABA (50micromol/kg). These results indicate that GABA prevents the development of ischemia/reperfusion-induced acute kidney injury presumably via GABA(B) receptor, by suppressing the enhanced renal sympathetic nerve activity during ischemia and the increased norepinephrine overflow from renal sympathetic nerve ending.

Pentobarbital reduces rhabdomyolysis-induced acute renal failure in conscious rats

BACKGROUND

Rhabdomyolysis is one of the causes of acute renal failure. Pentobarbital enhances the action of gamma-aminobutyric acid and suppresses the activities of nuclear factor (NF)-kappaB pathways. In this study, we used pentobarbital to study the effects on the glycerol-induced rhabdomyolysis with acute renal failure in conscious rats.

METHODS

Rhabdomyolysis was induced by intramuscular injection of 10 mL/kg of 50% glycerol in conscious rats. Ten minutes later, the rats received an intravenous injection of pentobarbital (10 mg/kg in 0.5 mL/h normal saline) or normal saline (0.5 mL/h). Biochemical substances, including blood urea nitrogen (BUN), creatinine (Cre), glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and creatine phosphokinase (CPK) were measured at 0 hour, 1 hour, 3 hours, 6 hours, 12 hours, 24 hours, and 48 hours. Rats were killed by decapitation at 48 hours after glycerol administration, and the kidneys were removed immediately for pathological findings and immunohistochemistry.

RESULTS

Intramuscular injection of glycerol significantly increased blood BUN, Cre, GOT, GPT, CPK levels and induced severe histopathologic damage in the kidneys. NF-kappaB and inducible nitric oxide synthase (iNOS) were increased, and E-cadherin was decreased after glycerol administration, as detected by immunohistochemistry in the kidneys. Posttreatment with pentobarbital decreased blood BUN, Cre, GOT, GPT, CPK levels, decreased the markers of kidney injury, and suppressed the release of NF-kappaB and iNOS after rhabdomyolysis.

CONCLUSION

Posttreatment with pentobarbital suppressed the activities of NF-kappaB and iNOS, decreased BUN, Cre, GOT, GPT, CPK levels, and decreased the markers of kidney injury after rhabdomyolysis. These actions ameliorated rhabdomyolysis-induced acute renal failure in conscious rats.

GAMMA.-Aminobutyric Acid Specifically Inhibits Progression of Tubular Fibrosis and Atrophy in Nephrectomized Rats

Gamma-aminobutyric acid (GABA) was administered orally to rats for 60 d after excision of five-sixths of their kidney volume. A decrease in renal function parameters was observed in these nephrectomized rats. However, the administration of GABA ameliorated renal dysfunction, and a longer administration period of GABA increased its protective effect. In addition, tubular fibrosis was markedly increased at 10 and 60 d in nephrectomized control rats, while GABA administration for 10 d reduced tubular fibrosis to the normal level. Tubular atrophy was markedly induced by nephrectomy, and was significantly reduced by the administration of GABA at 60 d. Furthermore, the nephrectomized control rats exhibited an increased expression level of transforming growth factor-beta1, where GABA significantly decreased it after administration for 10 d. The expression of fibronectin in the tubuli of rats administrated GABA for 60 d was completely and dose-dependently reduced as compared with nephrectomized control rats. However, the improvement effects in glomeruli were less. We also found that GABAA and GABAB receptors were specifically localized in tubuli. Specific agonists for GABAA and GABAB receptors improved renal function. These results suggest that GABA may have a beneficial effect on renal function in nephrectomized rats by inhibiting fibrosis and atrophy primarily in tubuli, and that it ameliorates losses of renal function in renal failure.