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Marc S Weinberg

Publications and source records attributed to Marc S Weinberg.

13 recordsLinked to original sources
PubMed2007

Specific inhibition of HBV replication in vitro and in vivo with expressed long hairpin RNA.

Activating RNA interference to achieve specific gene silencing has shown promise for the development of RNA-based treatment of chronic hepatitis B virus (HBV) infection. To further this approach, we assessed the efficacy of expressed long hairpin RNAs (lhRNAs) that target the conserved HBx open reading frame of HBV. As substrates for Dicer, lhRNAs have the potential to generate multiple short interfering RNAs (siRNAs) to enable simultaneous targeting of different sites. Two U6 Pol III vectors were constructed that encode anti-HBV lhRNAs with a 62 base pair stem sequence containing multiple G:U pairings. Assessment in transfected cultured cells and also in vivo using the murine hydrodynamic injection model showed that one of the lhRNA vectors (lhRNA 1) diminished markers of virus replication by 70-90% without evidence of interferon response induction. Greatest silencing efficacy was observed for targets that are complementary to sequences located at the base of the hairpin stem and this correlated with a higher concentration of siRNAs derived from this region of the lhRNA. Although lhRNA 1 has the advantage of targeting a greater viral sequence, incomplete cellular processing may result in unequal silencing across the span of the viral target RNA.

Animals↗
PubMed2006

Silencing of HIV-1 subtype C primary isolates by expressed small hairpin RNAs targeted to gag.

Discovery of sequence-specific silencing by activating the RNA interference (RNAi) pathway has led to exciting new strategies for treating infection with human immunodeficiency virus type 1 (HIV-1). Of the HIV-1 subtypes, C is especially common in areas of the world that are worst affected. Although prone to mutation, genome plasticity of this subtype is limited in functionally important regions. We identified conserved sequences within the HIV-1 subtype C gag open reading frame and assessed whether they are suitable targets for inhibition of viral replication by RNA Pol III-driven small hairpin RNAs (shRNAs). Initially, the efficacy of each of a panel of 10 shRNAs against HIV-1 was determined using a reporter assay. shRNAs A and B, which targeted the 5 end of gag, were most effective and were used to assess inhibition of replication in cultured cells of two R5 isolates (Du151 and Du422) and one X4 virus (SW7). These shRNAs diminished intracellular HIV-1 gag RNA and HIV-1 protein concentrations as well as p24 secretion by up to 80% without inducing an interferon response. However, shRNA-mediated knockdown efficacy against each of these viral isolates varied slightly. These data show successful activation of RNAi to inhibit the replication of biologically distinct HIV-1 subtype C isolates. The effector shRNAs described here are potential candidates for gene therapy applications against the most common global subtype of HIV-1.

Cell Line↗
PubMed2006

Are viral-encoded microRNAs mediating latent HIV-1 infection?

The Human Immunodeficiency Virus type 1 (HIV-1), a member of the lentivirus subfamily, infects both dividing and nondividing cells and, following reverse transcription of the viral RNA genome, integrates into the host chromatin where it enters into a latent state. Many of the factors governing viral latency remain unresolved and current antiviral treatment regimens are largely ineffective at eliminating cellular reservoirs of latent virus. The recent identification of microRNA (miRNA) encoding sequences embedded in the HIV-1 genome, and the discovery of functional virus-derived miRNAs, suggests a role for RNA Interference (RNAi) in the regulation of HIV-1 gene expression. Recently, the mammalian RNAi machinery was shown to regulate gene expression epigenetically by transcriptional modulation, providing a direct link between RNAi and a mechanism for inducing latency. Interestingly, both HIV-1 Tat, and the host TAR RNA-binding protein (TRBP), bind to the transactivating response (TAR) RNA of HIV-1 and affect the function of RNAi in human cells. Specifically, TRBP, a cofactor in Tat-TAR interactions, is a vital component of Dicer-mediated dsRNA processing. These novel observations support a central role for HIV-1 and associated host factors in regulating cellular RNAi and viral gene expression through RNA directed processes. Thus, HIV-1 may have evolved mechanisms to exploit the RNAi pathway at both the transcriptional and posttranscriptional level to affect and/or maintain a latent infection.

Gene Expression Regulation, Viral↗
PubMed2006

Long-term safety of high-dose angiotensin receptor blocker therapy in hypertensive patients with chronic kidney disease.

BACKGROUND: Reducing urinary protein excretion in patients with renal disease is an important therapeutic target to prevent the progression of renal and cardiovascular disease. Drugs such as angiotensin-converting enzyme inhibitors and angiotensin receptor blockers (ARBs), which block the actions of the renin-angiotensin-aldosterone system, are recommended because they reduce blood pressure and proteinuria. Recently, the use of higher doses of ARBs, up to three times the maximal approved dose, resulted in further reductions in protein excretion. Despite the effectiveness of this therapeutic approach, no long-term safety analysis has been conducted in patients receiving high-dose ARB treatment. OBJECTIVE: To study the long-term safety of high-dose ARB treatment. METHODS: We observed 48 patients [44 men and 4 women; ages 64 +/- 15 years (mean +/- SD), weight 88 +/- 28 kg, estimated glomerular filtration rate 53 +/- 23 ml/min] receiving treatment with high doses (1.5-5 times greater than the maximum approved dose) of ARBs, for 40 +/- 24 months (range 6-98 months). RESULTS: The average ARB dose tended to increase over time and was 3.2 +/- 1.2 times greater at the end of the study than that at the start. Systolic blood pressure was similar at the beginning and end of the study period (132 +/- 20 and 125 +/- 20 mmHg, respectively), but diastolic blood pressure showed a decrease throughout the study and was significantly reduced (P < 0.05) in association with 1.5x and 2x the maximum ARB dose (73 +/- 11 and 72 +/- 10 mmHg, respectively) when compared with baseline (78 +/- 11 mm Hg). There was a trend (P > 0.05) for increases in concentrations of serum potassium (0.2 +/- 0.9 mmol/l) and creatinine (0.3 +/- 0.7 mg/dl) with increases in dose from baseline to the end of the study. Serum creatinine concentration was greater (P < 0.05) at the periods of 3x and 4x the maximum dose, but this represented increases of only 12 and 20% from baseline, respectively. CONCLUSIONS: High-dose ARB treatment in patients with chronic renal disease is not associated with any clinically significant long-term negative effects on serum creatinine or potassium and is thus a important therapeutic modality with which to achieve further reductions in urinary protein excretion.

Adult↗
PubMed2006

Tilt determination in MEMS inertial vestibular prosthesis.

BACKGROUND: There is a clear need for a prosthesis that improves postural stability in the balance impaired. Such a device would be used as a temporary aid during recovery from ablative inner-ear surgery, a postural monitor during rehabilitation (for example, hip surgery), and as a permanent prosthesis for those elderly prone to falls. METHOD OF APPROACH: Recently developed, small instruments have enabled wearable prostheses to augment or replace vestibular functions. The current prosthesis communicates by vibrators mounted on the subject's trunk. In this paper we emphasize the unique algorithms that enable tilt indication with modestly performing micromachined gyroscopes and accelerometers. RESULTS: For large angles and multiple axes, gyro drift and unwanted lateral accelerations are successfully rejected. In single-axis tests, the most dramatic results were obtained in standard operating tests where balance-impaired subjects were deprived of vision and proprioceptive inputs. Balance-impaired subjects who fell (into safety restraints) when not aided were able to stand with the prosthesis. Initial multiaxis tests with healthy subjects have shown that sway is reduced in both forward-back and sideward directions. CONCLUSIONS: Positive results in initial testing and a sound theoretical basis for the hardware warrant continued development and testing, which is being conducted at three sites.

Acceleration↗
PubMed2005

The antisense strand of small interfering RNAs directs histone methylation and transcriptional gene silencing in human cells.

To determine mechanistically how siRNAs mediate transcriptional gene silencing (TGS) in human cells, we have measured histone methylation at targeted promoters, the dependency on active transcription, and whether or not both strands of the siRNA are required for siRNA-mediated TGS. We report here that siRNA treatment increases both H3K9 and H3K27 methylation of the targeted EF1A promoter and that this increase is dependent on nuclear specific delivery of the siRNA. We also find that TGS can be directed by the antisense strand alone, and requires active transcription by RNA polymerase II in human cells as evidenced by sensitivity to alpha-amanatin. The observation of antisense strand-specific siRNA-mediated TGS of EF1A was substantiated by targeting the U3 region of the HIV-1 LTR/promoter. Furthermore, we show that the antisense strand of siRNA EF52 associates with the transiently expressed Flag-tagged DNMT3A, the targeted EF1A promoter, and trimethylated H3K27. The observations reported here implicate a functional link between siRNA-mediated targeting of genomic regions (promoters), RNA Pol II function, histone methylation, and DNMT3A and support a paradigm in which the antisense strands of siRNAs alone can direct sequence-specific transcriptional gene silencing in human cells.

Amanitins↗
PubMed2005

Effective inhibition of HBV replication in vivo by anti-HBx short hairpin RNAs.

Exploiting the RNA interference pathway has shown promise for developing novel and effective treatment of hepatitis B virus (HBV) infection. To advance this approach, we analyzed the antiviral efficacy of a panel of 10 Pol III U6 promoter-encoded short hairpin RNAs (shRNAs) that target conserved sequences of the oncogenic HBx open reading frame. To facilitate intracellular processing, the shRNAs included mismatches in the 25-bp stem region and a terminal loop of miRNA-23. Two shRNAs (shRNA 5 and shRNA 6) showed knockdown of HBV markers by 80-100% in transfected hepatocytes and also in a murine hydrodynamic injection model of HBV replication. Intracellular processing of hairpin RNA with the intended strand bias correlated with antiviral efficacy. Moreover, markers of HBV replication were inhibited without inducing genes associated with the nonspecific interferon response. To assess the antiviral efficacy of the shRNAs in a context that is similar to natural HBV infection, shRNA-encoding cassettes were tested against the virus in a HBV transgenic murine model. When delivered using recombinant adenovirus vectors, U6 shRNA 5 and U6 shRNA 6 mediated significant HBV knockdown. Collectively, these observations indicate that U6 shRNA 5 and U6 shRNA 6 are promising candidates for therapy of chronic HBV infection.

Adenoviridae↗
PubMed2005

Comparative single-turnover kinetic analyses of trans-cleaving hammerhead ribozymes with naturally derived non-conserved sequence motifs.

trans-Cleaving hammerhead ribozyme variants were generated with mimicked non-conserved internal loop motifs derived from five structurally diverse natural cis-cleaving ribozymes. Most modified trans-cleaving variants showed enhanced single-turnover cleavage rates relative to minimal counterparts that lack tertiary interactions between internal loop motifs I and II, and relative to controls with sequence changes in loop I. The trans-cleaving ribozyme derived from the positive strand of peach latent mosaic viroid had the highest observed cleavage rate, suggesting a structurally optimized motif that facilitates rapid formation of the ribozyme catalytic center in a trans-reaction.

Animals↗
PubMed2004

Safety and tolerability of high-dose angiotensin receptor blocker therapy in patients with chronic kidney disease: a pilot study.

BACKGROUND: The progression of renal disease is ameliorated by drugs that inhibit the renin-angiotensin system (RAS). The doses used to slow the progression of renal disease may not completely suppress the RAS for 24 h and may explain why some patients do not obtain optimal renoprotective benefits from therapy. This pilot study was initiated to determine the safety and tolerability of using higher doses, than currently approved by the Food and Drug Administration, for the angiotensin-receptor blocker (ARB) candesartan cilexetil in patients with chronic kidney disease. We hypothesized that higher doses will be safe and well tolerated. Consequently, this should be a viable strategy for larger clinical trials evaluating the preservation of renal function. METHODS: Twelve patients (10 males; age = 57 +/- 14 years) with a history of diabetic or non-diabetic chronic kidney disease were enrolled in an 8-week open-label trial. Patients received candesartan titrated to a targeted dosage of 160 mg/day (5 times above the currently approved maximum dose) and remained at that dosage for the subsequent 4 weeks. The safety and tolerability of the higher doses were determined by measures of blood pressure, serum creatinine and potassium. RESULTS: Candesartan was well tolerated with no serious drug-related adverse events reported. Serum creatinine concentrations throughout the study were not different (p > 0.05) from baseline levels (2.0 +/- 0.5 mg/dl). Plasma potassium concentrations at 160 mg/day candesartan (4.9 +/- 0.7 mEq/l) were similar (p > 0.05) to those at baseline (4.8 +/- 0.5 mEq/l). CONCLUSIONS: The results of this pilot study suggest that supramaximal doses of ARBs are safe and well tolerated in patients with chronic kidney disease, while reducing both blood pressure and proteinuria. This study demonstrates the need to further investigate the optimal dosing strategy for ARBs in reducing the progression of renal disease.

Adult↗
PubMed2004

Antihypertensive efficacy of candesartan-lisinopril in combination vs. up-titration of lisinopril: the AMAZE trials.

The AMAZE (A Multicenter Trial Using Atacand and Zestril vs. Zestril to Evaluate the Effects on Lowering Blood Pressure) program included two identical studies sponsored by AstraZeneca LP. The oral form of candesartan is candesartan cilexetil; for simplicity, the term "candesartan" is used throughout this manuscript. Two identical multicenter, randomized, double-blind studies were performed to determine if addition of the angiotensin receptor blocker candesartan was more effective in lowering blood pressure than up-titration of lisinopril. Hypertensive patients (N=1,096) who were uncontrolled on lisinopril 20 mg daily were randomized (1:1) to receive either 8 weeks of high-dose lisinopril (40 mg) or the addition of candesartan (16 mg) for 2 weeks followed by 32 mg for 6 weeks. Study 1 (n=538) demonstrated decreases in trough sitting systolic/diastolic blood pressures at Week 8 by 6.2/5.9 mm Hg, respectively, for the lisinopril up-titration treatment group and by 11.6/8.3 mm Hg, respectively, for the lisinopril plus candesartan treatment group (p<0.01 in comparing both blood pressures reductions between the two treatment groups). Corresponding results for Study 2 (n=558) are reductions of 8.7/6.2 mm Hg and 9.5/7.4 mm Hg, respectively, for each of the two treatment groups. For Study 2, comparisons of systolic/diastolic blood pressures between the two treatment groups were not statistically significantly different (p=0.51/p=0.08, respectively). Post hoc pooled analysis (N=1,096) demonstrated a slightly greater blood pressure reduction with lisinopril plus candesartan compared with lisinopril (3.1/1.7 mm Hg). A 95% confidence interval limit for the difference in least squares mean change from baseline in systolic blood pressure between the two treatment groups is -4.8 to -1.5 and is -2.8 to -0.7 in mm Hg for diastolic blood pressure. The blood pressure control rates (<140/<90 mm Hg) were 42.7% and 36.9%, respectively. Both treatment regimens were well tolerated in all groups. In conclusion, for hypertensive patients not controlled by lisinopril 20 mg once daily, addition of candesartan (32 mg once daily) or doubling the dose of lisinopril provides safe, additional reduction of blood pressure.

Aged↗
PubMed2003

How high should an ACE inhibitor or angiotensin receptor blocker be dosed in patients with diabetic nephropathy?

Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), two drug classes that effectively block the actions of the renin-angiotensin system (RAS), have unique capabilities as antihypertensive agents. Recent landmark clinical trials have demonstrated their important roles as primary therapy for the prevention of renal disease in diabetes. The optimal dosage of these RAS blockers required to slow the progression of renal disease or impair the development of cardiovascular risk is not known. However, data from many studies strongly support the use of the higher doses of ACE inhibitors or ARBs to reduce proteinuria. All studies of kidney disease progression demonstrate benefit on slowing only when blood pressure is reduced when using higher doses. In order to accrue the optimum benefit from ACE inhibitors and ARBs, the dose-response relationship for diabetic renal disease will have to be determined. The best strategy, ie, supramaximal doses of ACE inhibitors or ARBs or combining them, is still a matter of debate but may be resolved soon by results of ongoing studies.

Albuminuria↗
PubMedDate not supplied

Acute and chronic renal failure.

Renal failure is defined as a deterioration of kidney function that results in the retention of nitrogenous waste products. It is increasingly prevalent in older populations, individuals with diabetes or hypertension, and postoperative patients. Therefore, podiatric physicians caring for these populations can expect to encounter this condition frequently. This article describes the epidemiology, causes, complications, and appropriate evaluation of renal failure relevant to a practicing podiatric physician. Also highlighted are treatment considerations, renal dosing of medications, and prevention of contrast nephropathy.

Acute Kidney Injury↗