A Glutathione Precursor Reduces Oxidative Injury to Cultured Embryonic Cardiomyocytes.

BACKGROUND: Newborn infants are highly vulnerable to oxidative stress. Following birth asphyxia, oxidative injury due to ischemia-reperfusion can result in significant brain and heart damage, leading to death or long-term disability. STUDY QUESTION: The study objective was to evaluate the effectiveness of antioxidant gamma-L-glutamyl-L-cysteine (γGlu-Cys) in inhibiting oxidative injury to cultured embryonic cardiomyocytes (H9c2 cells). STUDY DESIGN: Control and γGlu-Cys-treated (0.5 mM) H9c2 cells were incubated under 6-hour ischemic conditions followed by 2-hour simulated reperfusion. MEASURES AND OUTCOMES: To quantify oxidative stress-induced apoptosis sustained by cardiomyocytes, lactate dehydrogenase (LDH) release and the presence of cytosolic cytochrome c were measured, as well as the number of secondary lysosomes visualized under electron microscopy. RESULTS: Compared to controls, H9c2 cells coincubated with γGlu-Cys during ischemia-reperfusion exhibited a significant reduction in both LDH release into the incubation medium [23.88 ± 4.08 (SE) vs. 9.95 ± 1.86% of total; P = 0.02] and the number of secondary lysosomes [0.070 ± 0.009 (SD) vs. 0.043 ± 0.004 per µm; P = 0.01]. Inhibition of LDH release with γGlu-Cys was the same (P = 0.67) as that of a caspase inhibitor. The significant increase in cytosolic cytochrome c (P = 0.01) after ischemia-reperfusion simulation further supports γGlu-Cys's role in apoptosis prevention. CONCLUSIONS: It is concluded that the glutathione precursor γGlu-Cys protects cultured embryonic cardiomyocytes from apoptosis-associated oxidative injury.

Treatment with the matricellular protein CCN3 blocks and/or reverses fibrosis development in obesity with diabetic nephropathy.

Fibrosis is at the core of the high morbidity and mortality rates associated with the complications of diabetes and obesity, including diabetic nephropathy (DN), without any US Food and Drug Administration-approved drugs with this specific target. We recently provided the first evidence that the matricellular protein CCN3 (official symbol NOV) functions in a reciprocal manner, acting on the profibrotic family member CCN2 to inhibit fibrosis in a mesangial cell model of DN. Herein, we used the BT/BR ob/ob mouse as a best model of human obesity and DN progression to determine whether recombinant human CCN3 could be used therapeutically, and the mechanisms involved. Eight weeks of thrice-weekly i.p. injections (0.604 and 6.04 µg/kg of recombinant human CCN3) beginning in early-stage DN completely blocked and/or reversed the up-regulation of mRNA expression of kidney cortex fibrosis genes (CCN2, Col1a2, TGF-ß1, and PAI-1) seen in placebo-treated diabetic mice. The treatment completely blocked glomerular fibrosis, as determined by altered mesangial expansion and deposition of laminin. Furthermore, it protected against, or reversed, podocyte loss and kidney function reduction (rise in plasma creatinine concentration); albuminuria was also greatly reduced. This study demonstrates the potential efficacy of recombinant human CCN3 treatment in DN and points to mechanisms operating at multiple levels or pathways, upstream (eg, protecting against cell injury) and downstream (eg, regulating CCN2 activity and extracellular matrix metabolism).

In Vitro Studies on Degradation of Gamma-L-Glutamyl-L-Cysteine and Gamma-L-Glutamyl-D-Cysteine in Blood: Implications for Treatment of Stroke.

Treatment for ischemic stroke involves a thrombolytic agent to re-establish blood flow in the brain. However, delayed reperfusion may cause injury to brain capillaries. Previous studies indicate that the antioxidant gamma-L-glutamyl-L-cysteine (γ-Glu-Cys) contributes to reducing reperfusion injury to the cerebral vasculature in rats, when administered intravascularly. To determine the stability of γ-Glu-Cys in blood, the peptide was incubated in rat serum in vitro, and its degradation was quantified by high-pressure liquid chromatography. The half-time (t1/2) for degradation of γ-Glu-Cys was 11 ± 1 minute (mean ± SD, n = 3). A similar pattern of degradation was observed when γ-Glu-Cys was incubated in the presence of human plasma (t1/2 = 17 ± 8 minutes, n = 3). In a second series of experiments, degradation of an analog (γ-Glu-D-Cys) was tested in rat serum and found to be more stable than the native molecule. The initial velocity for degradation of γ-Glu-D-Cys (0.12 ± 0.02 mM/min; mean ± SD, n = 3) was significantly (P = 0.006) less than that of γ-Glu-Cys (0.22 ± 0.03 mM/min; mean ± SD, n = 3). Furthermore, an in vitro assay indicated that the analog has as an oxidative capacity that equals that of the original peptide in the presence of rat serum and human plasma. Finally, both peptides were found to be similarly effective in preventing lysis of intact cells using in vitro assays. These studies show that γ-Glu-Cys remains intact in blood for several minutes, and the analog γ-Glu-D-Cys may be a more stable, but similarly effective antioxidant.

Blood-brain barrier transport pathways for cytoprotective thiols.

The purpose of this study is to further define transport pathways for biological thiols by blood-brain barrier (BBB) endothelial cells, as a means of identifying endogenous cytoprotective mechanisms and potential therapeutic protocols for oxidative injury. Similar low-affininty, high-capacity passive carriers for glutathione (GSH) were observed at both the luminal (blood-facing) and abluminal (brain-facing) plasma membranes of BBB endothelial cells. These carriers are voltage dependent, favoring outward movement of intact peptide across both membrane domains, including efflux at the luminal plasmalemma where γ-glutamyl transpeptidase is located. Although present at both cell surfaces, the carriers are distributed unequally, with more appearing in the abluminal membrane. By contrast, high-affinity, low-capacity sodium-dependent GSH cotransport (Na-GSH) is observed only at the abluminal membrane, indicative of an inwardly directed active peptide carrier at the brain-facing plasma membrane. Treatment of cultured BBB endothelial cells with the GSH precursor γ-glutamyl-cysteine reduces cell damage under conditions simulating ischemia and reperfusion. These findings are consistent with the presence of (1) a typical γ-glutamyl cycle at the luminal membrane of BBB endothelial cells, (2) a significant efflux pathway at the abluminal membrane allowing passive movement of BBB GSH into brain extracellular fluid, (3) a Na-dependent, brain-to-blood pathway for transcellular transport of GSH, and (4) a mechanism for cytoprotection by γ-glutamyl cysteine, under conditions of ischemia and reperfusion.

CCN3 (NOV) is a negative regulator of CCN2 (CTGF) and a novel endogenous inhibitor of the fibrotic pathway in an in vitro model of renal disease.

Fibrosis is a major cause of end-stage renal disease, and although initiation factors have been elucidated, uncertainty concerning the downstream pathways has hampered the development of anti-fibrotic therapies. CCN2 (CTGF) functions downstream of transforming growth factor (TGF)-beta, driving increased extracellular matrix (ECM) accumulation and fibrosis. We examined the possibility that CCN3 (NOV), another CCN family member with reported biological activities that differ from CCN2, might act as an endogenous negative regulator of ECM and fibrosis. We show that cultured rat mesangial cells express CCN3 mRNA and protein, and that TGF-beta treatment reduced CCN3 expression levels while increasing CCN2 and collagen type I activities. Conversely, either the addition of CCN3 or CCN3 overexpression produced a marked down-regulation of CCN2 followed by virtual blockade of both collagen type I transcription and its accumulation. This finding occurred in both growth-arrested and CCN3-transfected cells under normal growth conditions after TGF-beta treatment. These effects were not attributable to altered cellular proliferation as determined by cell cycle analysis, nor were they attributable to interference of Smad signaling as shown by analysis of phosphorylated Smad3 levels. In conclusion, both CCN2 and CCN3 appear to act in a yin/yang manner to regulate ECM metabolism. CCN3, acting downstream of TGF-beta to block CCN2 and the up-regulation of ECM, may therefore serve to naturally limit fibrosis in vivo and provide opportunities for novel, endogenous-based therapeutic treatments.

Effect of N-acetylcysteine route of administration on chemoprotection against cisplatin-induced toxicity in rat models.

Dosing and route of administration of N-acetylcysteine (NAC) for protection against cisplatin (CDDP) nephrotoxicity was investigated in rats. Two models of toxicity were tested: a single high dose of CDDP (10 mg/kg intraperitoneally (IP)), and multiple low dose treatments (1 mg/kg IP twice a day for 4 days, 10 days rest, then repeated). NAC (50-1,200 mg/kg) was given to the rats by IP, oral (PO), intravenous (IV) and intra-arterial (IA) routes. Renal toxicity was determined by blood urea nitrogen (BUN) and creatinine (CR) levels 3 days after treatment. Blood collected 15 min after NAC was analyzed for total NAC. Both models of CDDP administration produced renal toxicity. In the single dose CDDP model, NAC 400 mg/kg given IP and PO produced no renal protection as measured by BUN (131.8 +/- 8.2 and 123.3 +/- 8.2, respectively) or CR (2.3 +/- 0.38 and 1.77 +/- 0.21, respectively). IV NAC reduced nephrotoxicity, (BUN 26.3 +/- 6.8, CR 0.47 +/- 0.15). NAC 50 mg/kg IA gave better protection than IV. In the repeated-dose CDDP model, nephrotoxicity was blocked by 800 mg/kg NAC given IV but not IP. Blood concentrations of total NAC showed a dose response after IV NAC, but high dose NAC (1,200 mg/kg) by the PO route gave very low levels of NAC. Thus the protective properties of NAC are affected by the dose and route of administration.

New frontiers in translational research in neuro-oncology and the blood-brain barrier: report of the tenth annual Blood-Brain Barrier Disruption Consortium Meeting.

The blood-brain barrier (BBB) presents a major obstacle to the treatment of malignant brain tumors and other central nervous system (CNS) diseases. For this reason, a meeting partially funded by an NIH R13 grant was convened to discuss recent advances and future directions in translational research in neuro-oncology and the BBB. Cell biology and transport across the BBB, delivery of agents to the CNS, neuroimaging, angiogenesis, immunotherapy, and gene therapy, as well as glioma, primary CNS lymphoma, and metastases to the CNS were discussed. Transport across the BBB relates to the neurovascular unit, which consists not only of endothelial cells but also of pericyte, glia, and neuronal elements.

Targeted delivery in primary and metastatic brain tumors: summary report of the seventh annual meeting of the Blood-Brain Barrier Disruption Consortium.

The November 2000 NIH report of the Brain Tumor Progress Review Group identified delivering and targeting therapeutic agents as a priority in the treatment of malignant brain tumors. For this reason, the seventh annual Blood-Brain Barrier Disruption Consortium meeting, partially funded by an NIH R13 Grant, focused on recent advances in targeted delivery to the central nervous system, clinical trials for primary and metastatic brain tumors using enhanced chemotherapy delivery, and strategies to lessen the toxicities associated with dose intensive treatments, using thiols.

CCN3/CCN2 regulation and the fibrosis of diabetic renal disease.

Prior work in the CCN field, including our own, suggested to us that there might be co-regulatory activity and function as part of the actions of this family of cysteine rich cytokines. CCN2 is now regarded as a major pro-fibrotic molecule acting both down-stream and independent of TGF-beta1, and appears causal in the disease afflicting multiple organs. Since diabetic renal fibrosis is a common complication of diabetes, and a major cause of end stage renal disease (ESRD), we examined the possibility that CCN3 (NOV), might act as an endogenous negative regulator of CCN2 with the capacity to limit the overproduction of extracellular matrix (ECM), and thus prevent, or ameliorate fibrosis. We demonstrate, using an in vitro model of diabetic renal fibrosis, that both exogenous treatment with CCN3 and transfection with the over-expression of the CCN3 gene in mesangial cells markedly down-regulates CCN2 activity and blocks ECM over-accumulation stimulated by TGF-beta1. Conversely, TGF-beta1 treatment reduces endogenous CCN3 expression and increases CCN2 activity and matrix accumulation, indicating an important, novel yin/yang effect. Using the db/db mouse model of diabetic nephropathy, we confirm the expression of CCN3 in the kidney, with temporal localization that supports these in vitro findings. In summary, the results corroborate our hypothesis that one function of CCN3 is to regulate CCN2 activity and at the concentrations and conditions used down-regulates the effects of TGF-beta1, acting to limit ECM turnover and fibrosis in vivo. The findings suggest opportunities for novel endogenous-based therapy either by the administration, or the upregulation of CCN3.

N-acetylcysteine use to prevent contrast medium-induced nephropathy: premature phase III trials.

To date there has been no general consensus regarding the effectiveness of N-acetylcysteine as a protective therapy against contrast medium-induced nephropathy. Several phase III clinical trials have been conducted without a proper understanding of N-acetylcysteine pharmacology, particularly with regard to first-pass hepatic metabolism. A review was conducted of the literature concerning contrast medium-induced nephropathy and new studies of human N-acetylcysteine pharmacology were performed. After an analysis was performed, it was concluded that further phase I and phase II trials are needed. The efficacy of N-acetylcysteine in the prevention of contrast medium-induced nephropathy may be demonstrated with the use of higher doses than used in earlier studies, in combination with parenteral administration.

Delivery of chemotherapy and antibodies across the blood-brain barrier and the role of chemoprotection, in primary and metastatic brain tumors: report of the Eleventh Annual Blood-Brain Barrier Consortium meeting.

Although knowledge of molecular biology and cellular physiology has advanced at a rapid pace, much remains to be learned about delivering chemotherapy and antibodies across the blood-brain barrier (BBB) for the diagnosis and treatment of central nervous system (CNS) disease. A meeting, partially funded by an NIH R13 grant, was convened to discuss the state of the science, current knowledge gaps, and future directions in the delivery of drugs and proteins to the CNS, for the treatment of primary and metastatic brain tumors. Meeting topics included CNS metastases and the BBB, and chemoprotection and chemoenhancement in CNS disorders. The discussions regarding CNS metastases generated possibilities of chemoprotection as a means not only to decrease treatment-related toxicity but also to increase chemotherapy dose intensity. The increasing incidence of sanctuary brain metastasis from breast cancer, in part due to the difficulty of monoclonal antibodies (mAbs) such as herceptin to cross the BBB, was one of the most salient "take home" messages of the meeting.

The complementary membranes forming the blood-brain barrier.

Brain capillary endothelial cells form the blood-brain barrier. They are connected by extensive tight junctions, and are polarized into luminal (blood-facing) and abluminal (brain-facing) plasma membrane domains. The polar distribution of transport proteins allows for active regulation of brain extracellular fluid. Experiments on isolated membrane vesicles from capillary endothelial cells of bovine brain demonstrated the polar arrangement of amino acid and glucose transporters, and the utility of such arrangements have been proposed. For instance, passive carriers for glutamine and glutamate have been found only in the luminal membrane of blood-brain barrier cells, while Na-dependent secondary active transporters are at the abluminal membrane. This organization could promote the net removal of nitrogen-rich amino acids from brain, and account for the low level of glutamate penetration into the central nervous system. Furthermore, the presence of a gamma-glutamyl cycle at the luminal membrane and Na-dependent amino acid transporters at the abluminal membrane may serve to modulate movement of amino acids from blood-to-brain. Passive carriers facilitate amino acid transport into brain. However, activation of the gamma-glutamyl cycle by increased plasma amino acids is expected to generate oxoproline within the blood-brain barrier. Oxoproline stimulates secondary active amino acid transporters (Systems A and B(o)+) at the abluminal membrane, thereby reducing net influx of amino acids to brain. Finally, passive glucose transporters are present in both the luminal and abluminal membranes of the blood-brain barrier. Interestingly, a high affinity Na-dependent glucose carrier has been described only in the abluminal membrane. This raises the question whether glucose entry may be regulated to some extent. Immunoblotting studies suggest more than one type of passive glucose transporter exist in the blood-brain barrier, each with an asymmetrical distribution. In conclusion, it is now clear that the blood-brain barrier participates in the active regulation of brain extracellular fluid, and that the diverse functions of each plasma membrane domain contributes to these regulatory functions.

Bone marrow chemoprotection without compromise of chemotherapy efficacy in a rat brain tumor model.

Thiol chemoprotective agents can reduce chemotherapy side effects, but clinical use is limited due to concerns of impaired chemotherapeutic efficacy. We evaluated whether an optimized bone marrow chemoprotection regimen impaired the efficacy of enhanced chemotherapy against rat brain tumors. Nude rats with intracerebral human lung carcinoma xenografts were treated with carboplatin, melphalan, and etoposide phosphate delivered intra-arterially with osmotic blood-brain barrier disruption (n = 8/group). Thiol chemoprotection was N-acetyl-L-cysteine (1000 mg/kg) 60 min before chemotherapy and/or sodium thiosulfate (8 g/m(2)) 4 and 8 h after chemotherapy, when the blood-brain barrier is reestablished. Blood counts were obtained before treatment on day 3 and at sacrifice on day 9. N-acetylcysteine serum clearance half-life was 9 to 11 min. Pretreatment with N-acetylcysteine combined with delayed administration of sodium thiosulfate protected against toxicity toward total white cells, granulocytes, and platelets (P = 0.0016). Enhanced chemotherapy reduced intracerebral tumor volume to 4.3 +/- 1.0 mm(3) compared with 29.1 +/- 4.1 mm(3) in untreated animals (P < 0.0001). Tumor volume was 3.7 +/- 0.6 mm(3) in rats that received N-acetylcysteine before and sodium thiosulfate after chemotherapy. The data indicate the efficacy of enhanced chemotherapy for rat brain tumors was not affected by thiol chemoprotection that provided excellent protection for hematological toxicity. Negative interactions of thiols with antitumor efficacy were avoided by temporal and spatial separation of chemoprotectants and chemotherapy.