Biomedical subjects

Zain Paroo

Publications and source records attributed to Zain Paroo.

7 recordsLinked to original sources

PubMed2004

Biodistribution of phosphodiester and phosphorothioate siRNA.

Short interfering RNAs (siRNAs) are valuable tools for analyzing protein function in mammalian cell culture. This success has led to high expectations for in vivo and therapeutic applications. However, the pharmacokinetic properties of siRNA are not known. Here we report the biodistribution of a phosphodiester (PO) siRNA duplex and examine the effect of phosphorothioate (PS) linkages. Our findings indicate that biodistribution of siRNA is similar to that for single-stranded antisense oligonucleotides and offer insights for use of siRNA in vivo.

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PubMed2004

Challenges for RNAi in vivo.

Synthetic small interfering RNA (siRNA) has become a valuable tool for investigating gene function in cell culture. This success has led to high expectations for siRNA as a tool for in vivo investigation and as a platform for therapeutic development. siRNA in cell culture owes much of its success to years of development of traditional antisense oligonucleotides, and in vivo applications will also benefit from previous experience in this regard. However, the duplex nature of siRNA presents significant obstacles that will need to be overcome. Here, we discuss the current status of in vivo siRNA technology and describe some of the barriers to widespread application of RNAi-mediated gene silencing in mammals.

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PubMed2004

Validating bioluminescence imaging as a high-throughput, quantitative modality for assessing tumor burden.

Bioluminescence imaging (BLI) is a highly sensitive tool for visualizing tumors, neoplastic development, metastatic spread, and response to therapy. Although BLI has engendered much excitement due to its apparent simplicity and ease of implementation, few rigorous studies have been presented to validate the measurements. Here, we characterize the nature of bioluminescence output from mice bearing subcutaneous luciferase-expressing tumors over a 4-week period. Following intraperitoneal or direct intratumoral administration of luciferin substrate, there was a highly dynamic kinetic profile of light emission. Although bioluminescence was subject to variability, strong correlations (r >.8, p <.001) between caliper measured tumor volumes and peak light signal, area under light signal curve and light emission at specific time points were determined. Moreover, the profile of tumor growth, as monitored with bioluminescence, closely resembled that for caliper measurements. The study shows that despite the dynamic and variable nature of bioluminescence, where appropriate experimental precautions are taken, single time point BLI may be useful for noninvasive, high-throughput, quantitative assessment of tumor burden.

Animals↗

PubMed2003

Imaging gene expression using oligonucleotides and peptide nucleic acids.

The development of methods for non-invasive, real-time imaging of gene expression would provide powerful tools for biomedical research and medical diagnostics. A broadly applicable strategy for achieving this goal is the use of complementary oligonucleotide probes for recognition of mRNA. The major challenge for molecular imaging is the development of specific and efficient transducers for signaling probe-target interaction. This review summarizes the strengths and limitations of reported molecular approaches for imaging of mRNA expression and discusses the challenges to development of in vivo methods.

Animals↗

PubMed2002

Exercise improves postischemic cardiac function in males but not females: consequences of a novel sex-specific heat shock protein 70 response.

Exercise is a physiological inducer of the cardioprotective heat shock protein, Hsp70. The putative biological events involved in signaling this response exhibit sexual dimorphism. Thus, it was hypothesized that exercise-mediated induction of Hsp70 would demonstrate sex specificity. After treadmill running, male rats exhibited 2-fold greater levels of cardiac Hsp70 relative to the levels in gonadally intact female rats (P<0.001). Ovariectomized female rats exhibited exercise-mediated induction of Hsp70 similar to that observed for male rats, and estrogen treatment in these female rats reversed this effect (P<0.001). Attenuation of Hsp70 signaling by estrogen was non-receptor-mediated, possibly involving a cellular membrane-stabilizing mechanism of action. The physiological importance of this sex-specific hormone-mediated stress response is underscored by the disparity in functional adaptation in response to exercise between male rats and female rats. Exercise markedly improved postischemic left ventricular developed pressure, the maximal rate of contraction, and maximal rate of relaxation, and it reduced left ventricular end-diastolic pressure in male rats (P<0.001). No such benefit of exercise was observed in intact female rats. A causal role for Hsp70 in this sex-specific cardioprotective adaptation was indicated, inasmuch as ablation of Hsp70 induction with antisense oligonucleotides designed against Hsp70 transcripts attenuated improvement in the recovery of cardiac function in exercised male rats (P<0.05). Thus, the sex-specific hormone-mediated Hsp70 response to exercise results in cardioprotective adaptation, preferentially in male rats relative to female rats. These findings suggest that exercise may be more important for males than for females in defending against the effects of heart disease and offer a novel manner by which males may reduce the sex gap in susceptibility to adverse cardiac events.

Animals↗

PubMed2002

Redox signaling of cardiac HSF1 DNA binding.

Experiments involving chemical induction of the heat shock response in simple biological systems have generated the hypothesis that protein denaturation and consequential binding of heat shock transcription factor 1 (HSF1) to proximal heat shock elements (HSEs) on heat shock protein (hsp) genes are the result of oxidation and/or depletion of intracellular thiols. The purpose of the present investigation was to determine the role of redox signaling of HSF1 in the intact animal in response to physiological and pharmacological perturbations. Heat shock and exercise induced HSF1-HSE DNA binding in the rat myocardium (P < 0.001) in the absence of changes in reduced glutathione (GSH), the major nonprotein thiol in the cell. Ischemia-reperfusion, which decreased GSH content (P < 0.05), resulted in nonsignificant HSF1-HSE formation. This dissociation between physiological induction of HSF1 and changes in GSH was not gender dependent. Pharmacological ablation of GSH with L-buthionine-[S,R]-sulfoximine (BSO) treatment increased myocardial HSF1-HSE DNA binding in estrogen-naive animals (P = 0.007). Thus, although physiological induction of HSF1-HSE DNA binding is likely regulated by mediators of protein denaturation other than cellular redox status, the proposed signaling pathway may predominate with pharmacological oxidation and may represent a plausible and accessible strategy in the development of HSP-based therapies.

Animals↗

PubMed2002

Estrogen attenuates postexercise HSP70 expression in skeletal muscle.

Exercise has been demonstrated as a physiological inducer of heat shock protein (HSP)70. Many of the proposed signals of this response exhibit sexual dimorphism. Thus the present objectives were to determine whether HSP70 induction after exercise exhibits gender specificity and to elucidate the mechanisms underlying such a phenomenon. Postexercise HSP70 induction in skeletal muscle was greater in male than female rats at the level of protein and mRNA (P = 0.005). Moreover, placebo-treated ovariectomized animals demonstrated a greater HSP70 response to exercise than those treated with estrogen (P = 0.015 and 0.019 for protein and mRNA, respectively). These findings indicate that the gender-specific HSP70 response to exercise is mediated by the female-specific hormone estrogen. Compounds structurally related to 17beta-estradiol, the major endogenous estrogen, but which do not activate the estrogen receptor, also attenuated HSP70 induction with exercise (P < 0.01), indicating a nongenomic hormonal mechanism. These findings highlight a specific example of the biological differences between males and females and reiterate the physiological effects of sex hormones extending beyond their roles in reproductive function.

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