Metabolomics for identifying pathways involved in vesicating agent lewisite-induced corneal injury

Lewisite (LEW) is an arsenical vesicant that can be a potentially dangerous chemical warfare agent (CWA). Eyes are particularly susceptible to vesicant induced injuries and ocular LEW exposure can act swiftly, causing burning of eyes, edema, inflammation, cell death and even blindness. In our previous studies, we developed a LEW exposure-induced corneal injury model in rabbit and showed increased inflammation, neovascularization, cell death, and structural damage to rabbit corneas upon LEW exposure. In the present study, we further assessed the metabolomic changes to delineate the possible mechanisms underlying the LEW-induced corneal injuries. This information is vital and could help in the development of effective targeted therapies against ocular LEW injuries. Thus, the metabolomic changes associated with LEW exposures in rabbit corneas were assessed as a function of time, to delineate pathways from molecular perturbations at the genomic and proteomic levels. New Zealand white rabbit corneas (n = 3-6) were exposed to LEW vapor (0.2 mg/L; flow rate: 300 ml/min) for 2.5 min (short exposure; low dose) or 7.5 min (long-exposure; high dose) and then collected at 1, 3, 7, or 14 days post LEW exposure. Samples were prepared using the automated MicroLab STAR® system, and proteins precipitated to recover the chemically diverse metabolites. Metabolomic analysis was carried out by reverse phase UPLC-MS/MS and gas chromatography (GC)-MS. The data obtained were analyzed using Metabolon's software. The results showed that LEW exposures at high doses were more toxic, particularly at the day 7 post exposure time point. LEW exposure was shown to dysregulate metabolites associated with all the integral functions of the cornea and cause increased inflammation and immune response, as well as generate oxidative stress. Additionally, all important metabolic functions of the cells were also affected: lipid and nucleotide metabolism, and energetics. The high dose LEW exposures were more toxic, particularly at day 7 post LEW exposure (>10-fold increased levels of histamine, quinolinate, N-acetyl-β-alanine, GMP, and UPM). LEW exposure dysregulated integral functions of the cornea, caused inflammation and heightened immune response, and generated oxidative stress. Lipid and nucleotide metabolism, and energetics were also affected. The novel information about altered metabolic profile of rabbit cornea following LEW exposure could assist in delineating complex molecular events; thus, aid in identifying therapeutic targets to effectively ameliorate ocular trauma.

[Chronic hepatitis B and D (delta) : Current and future treatments]

BACKGROUND

Worldwide, hepatitis B virus (HBV) infection is among the 30 leading causes of death, despite effective vaccination and therapeutic options. Chronic hepatitis delta (coinfection with hepatitis D virus) leads to a rapid disease progression.

AIMS

Based on current international guidelines and studies, an overview about present and future therapeutic options for chronic hepatitis B and delta is provided.

RESULTS

Therapy with nucleoside or nucleotide analogues leads to nearly complete HBV DNA suppression, which is associated with regression of liver fibrosis and a lower risk for the development of hepatocellular carcinoma. Therapy of chronic hepatitis delta with pegylated interferon alfa achieves only low response rates with high risk for virological relapse. Various therapeutic approaches are currently being investigated in preclinical and clinical studies and have led to a significant reduction of hepatitis B surface antigen (HBsAg) and HDV RNA.

CONCLUSION

Current therapies of chronic HBV infection can effectively reduce subsequent complications. New therapeutic approaches promise functional cure (HBsAg loss) of HBV infection and effective treatment options for patients with chronic hepatitis delta.

Bone Mineral Density and Renal Function in Chronic Hepatitis B Patients Receiving Nucleotide versus Nucleoside Analogs: A Pilot Prospective Study

BACKGROUND

The use of nucleotide analogs (NTAs) can be associated with negative effects on renal function and bone mineral density (BMD) due to proximal tubular dysfunction and hypophosphatemia; however, prospective data assessing the bone and renal safety of these agents are limited.

OBJECTIVE

This study aimed to evaluate the prevalence of bone diseases among chronic hepatitis B (CHB) patients without cirrhosis and the changes in BMD and glomerular filtration rate (GFR) between patients receiving NTAs versus nucleoside analogs (NSAs).

MATERIAL AND METHOD

We prospectively collected data from non-cirrhotic CHB patients who had been treated for < 1 year in Rajavithi Hospital (Bangkok, Thailand) between 2012 and 2014. Patients with significant comorbidities or those being treated for bone diseases were excluded. BMD assessment was performed at the lumbar spine (LS) and femoral neck (FN). BMD T-scores were used to define osteopenia (-2.5 to -1) and osteoporosis (< -2.5), and the GFR was estimated using the Cockcroft-Gault method.

RESULTS

Twenty patients were included: 65% were men; 40% were HBeAg positive; and the median age was 42.7 (25.6-64.2) years. Ten patients had been treated with NTAs (7 with tenofovir 3 with adefovir) and 10 patients had been treated with NSAs (8 with lamivudine, 2 with entecavir), with a median follow-up period of 1.5 years (1.2-1.6). At baseline, the overall prevalence of osteopenia was 45% and the median GFR was 94 (51-144) mL/min. BMD in CHB patients was slightly lower than in an age-matched population based on Z-scores. Changes in LS-BMD and FN-BMD were not significantly different between groups. The annual reduction in GFR was more pronounced in the NTA group (-7.4% vs. -1.39%, p = 0.018).

CONCLUSION

Osteopenia is common in CHB patients without cirrhosis. Changes in BMD were not significantly different between groups. The annual reduction in GFR was more pronounced in the NTA group.

Impact of nucleos(t)ide analogue combination therapy on the estimated glomerular filtration rate in patients with chronic hepatitis B

Monotherapy with telbivudine or adefovir can affect estimated the glomerular filtration rate (eGFR). However, only a few studies have assessed changes in eGFR in patients who have chronic hepatitis B (CHB) and are receiving nucleos(t)ide analogue (NA) combination therapy. In our study, we aimed to evaluate the effects of long-term NA combination therapy on eGFR in Chinese CHB patients. This retrospective study included 195 CHB patients. Patient subgroups included those treated with lamivudine plus adefovir (n = 73), telbivudine plus adefovir (n = 51), and entecavir plus adefovir (n = 35); untreated patients (n = 36) served as a control group. After an average follow-up duration of 24 months with combination therapy, analysis of changes in eGFR from baseline values, calculated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and Modification of Diet in Renal Disease (MDRD) formulas, showed decrease by 11.08 and 18.34 mL/min (P < .001), respectively, in the lamivudine plus adefovir group; decrease by 3.73 and 10.04 mL/min (P = .012), respectively, in the entecavir plus adefovir group; and increase by 0.91 and 2.12 mL/min (P = .46), respectively, in the telbivudine plus adefovir group. The eGFR in the telbivudine plus adefovir group was similar to that for the untreated group. The eGFR decreases due to adefovir therapy could be rescued by adding telbivudine, and the eGFR increase due to telbivudine could be compromised by adding adefovir. Adefovir in combination with lamivudine or entecavir therapy was significantly associated with decreased eGFR, but telbivudine could rescue the eGFR decrease that results from adefovir treatment.

Mitochondrial dysfunction: patient monitoring and toxicity management

Mitochondrial toxicity has been implicated in the development of a variety of nucleoside reverse transcriptase inhibitor-associated syndromes. Mitochondrial damage and decreases in mitochondrial DNA levels have been demonstrated in various tissues of patients treated with NRTIs, especially in conjunction with exposure to stavudine. Clinical syndromes that may be mediated by mitochondrial toxicity include hyperlactatemia and lactic acidosis, hepatic steatosis, lipoatrophy, peripheral neuropathy, HIV-associated neuromuscular weakness syndrome, pancreatitis, skeletal myopathies, and cardiomyopathy. Early recognition of these syndromes in their mild forms involves close monitoring and a high index of suspicion. This may allow prompt discontinuation of the causative agent(s) and initiation of appropriate therapeutic measures, thereby increasing the chances of reversibility of the syndrome.

Toxicity of antiretroviral nucleoside and nucleotide analogues: is mitochondrial toxicity the only mechanism?

Nucleoside analogues represent the cornerstones of antiretroviral regimens. A range of drug- or tissue-specific toxicities, such as peripheral neuropathy, myopathy, pancreatitis and lactic acidosis with hepatic steatosis, has been documented with these agents. The fat atrophy seen on long term antiretroviral therapy may also be related to nucleoside analogues. The mechanisms by which nucleoside analogues cause toxicity are not clearly established. In vitro, the triphosphates of these agents are weak to modest substrates for human DNA polymerases, showing the greatest affinity for mitochondrial DNA polymerase gamma. Short term exposure in vitro to some nucleoside analogues has been demonstrated to cause increased lactate production or falls in mitochondrial DNA suggestive of mitochondrial toxicity. However, stavudine and to a lesser extent zidovudine are poor substrates for mitochondrial thymidine kinase type 2, the predominant form in cells that are not actively mitotic such as neurons, myocytes and adipocytes. These are the cell types where the proposed mitochondrial toxicities neuropathy, myopathy and lipoatrophy are observed. Thus, active concentrations of phosphorylated products of stavudine and zidovudine may not be present in mitochondria. The familial mitochondrial diseases do not have identical presentations to nucleoside analogue toxicities. These disorders most commonly involve the CNS, typically with seizures or dementia, and occasionally the kidneys. Although nucleoside analogues are known to penetrate the CNS and are commonly renally excreted unchanged, mitochondrial toxicities at these sites have not been documented. Furthermore, toxicity caused by nucleoside or nucleotide analogues does not always appear to arise through the mitochondrial route. Cidofovir appears to cause renal tubular dysfunction via a toxic intracellular metabolite, and zidovudine-related anaemia appears to be related to decreased globin RNA synthesis. In vitro or animal models suggest that zidovudine myopathy, stavudine-related (but not zalcitabine- or didanosine-related) neuropathy and didanosine-related pancreatitis may all be not related, or not exclusively related, to mitochondrial dysfunction. The integration of nucleoside analogues into nuclear DNA, best documented with zidovudine but likely to occur with other agents, represents an alternative but potentially delayed pathway to cytotoxicity and cell apoptosis. This is the mechanism of cell death during therapy with antineoplastic nucleoside analogues, and may have contributed to the multisystem toxicities observed with the anti-hepatitis B drug fialuridine. New research evaluating the effects of long term exposure of cell lines is required to address the possibility that nuclear genotoxicity plays a role in long term nucleoside analogue toxicity.

Dietary nucleotides augment dextran sulfate sodium-induced distal colitis in rats

We have previously shown that enteral and parenteral supplementation of nucleotides (NT) accelerates healing of small-bowel ulcers in rats with indomethacin-induced ileitis. The purpose of this study was to evaluate whether dietary NT supplementation would similarly affect ulcer healing in dextran sulfate sodium (DSS)-induced colitis in rats. Male Sprague-Dawley rats were randomly assigned to receive either nucleotide-free (NF) or NT-supplemented diets. After 2 d of prefeeding, colitis was induced by including 40 g/L of DSS in drinking water for 3 d, followed thereafter by tap water. Rats from each group were killed at 7 and 12 d after induction of colitis. Additional rats were also used for both the groups as controls (untreated groups). The length of colon was measured and evaluated by histological score. Colonic myeloperoxidase (MPO) activity was assessed. In a separate series of experiments, rats were studied at 0, 4, 7, and 12 d for interleukin-1beta (IL-1beta) in rectal dialysate and plasma. Ulceration predominated in the distal colon in DSS-treated rats. There was no significant difference between the histological scores of the NF and NT-supplemented groups either at 7 or 12 d. MPO activity at 7 and 12 d was significantly higher in the NT-supplemented compared to NF group (7 d: 1013 +/- 172 vs. 409.9 +/- 103.2; 12 d: 471.9 +/- 112.4 vs. 223.6 +/- 21.6 units. min-1. g colon-1). IL-1beta concentration in rectal dialysate was significantly higher at 7 d in both groups compared to 0 and 4 d. At 12 d it continued to be significantly elevated in the NT-supplemented group and was greater than in the NT-free group. Our data on the proinflammatory cytokine, in conjunction with MPO activity, strongly suggest that NT supplementation aggravates the severity of DSS-induced colitis in rats.