Expression of constitutive heat shock protein-70 in normal (non-stressed) rabbit urinary bladder tissue

THE MOLECULAR GENETIC BASIS OF MITOCHONDRIAL MALFUNCTION IN BLADDER TISSUE FOLLOWING OUTLET OBSTRUCTION

PURPOSE

Bladder dysfunction following partial outlet obstruction is a frequent consequence of benign prostatic hyperplasia and an increasingly common problem given the aging of the general population. Recent studies from this and other groups have begun to elucidate the molecular bases for the well described physiological malfunctions that characterize this clinical entity. We summarized and synthesized that information.

MATERIALS AND METHODS

Using modern methods of molecular genetics, including real-time polymerase chain reaction, real-time reverse transcriptase-polymerase chain reaction and others, as well as traditional experimental techniques such as electron microscopy we and others examined the transcriptional profile, morphology, etc of bladder smooth muscle mitochondria in experimental models of outlet obstruction.

RESULTS

Data from many studies have demonstrated that aberrant gene expression in the mitochondrial and mitochondria related nuclear genetic systems underlies the loss of compliance and other attributes of bladder dysfunction following outlet obstruction. Such aberrant transcriptional characteristics engender loss of function in the electron transport and oxidative phosphorylation systems. Morphological studies of mitochondria in the animal model systems support this conclusion.

CONCLUSIONS

In large part the loss of function in bladder smooth muscle following outlet obstruction results from the attenuation of mitochondrial energy production. In this article we reviewed and synthesized all available experimental observations relevant to this problem and we suggest future lines of inquiry that should prove fruitful in developing new strategies to treat the condition.

Estudio experimental de la expresión de las proteínas de la pared vesical en la obstrucción del tracto urinario inferior en el conejo

OBJECTIVES

To determine the relationship of the bladder wall levels of the contractile proteins: whole actin, beta-actin, alpha-sarcomeric-actina caldesmon and of the Heat Stress Protein HSP-70, with the partial bladder outlet obstruction.

MATERIAL AND METHODS

It was carried out an experimental study on 43 New-Zealand rabbits. These animals were divided into a control group and six experimental groups with partial bladder outlet obstruction induced by an incomplete tie around the urethra. The experimental groups were defined according the day when the animals were sacrified: at 24 hours, 7 days, 15 days, 1 month, 3 months and 6 months of the obstruction. It was determined in all animals the muscular bladder wall concentration of whole actin, beta-actin, alpha-sarcomeric-actin, caldesmon and HSP-70 protein, according to Western Blotting technique. The results were analyzed by means of ANOVA, using the Scheffe post hoc method.

RESULTS

The bladder weight of the obstructed animals increased significantly in two stages: until the day 15 and between the day 15 and the end of the study, corresponding to theoretical phases of initial hypertrophy and compensation. The level of whole actin showed a significant decrease at the beginning of compensation phase, while the beta-actin level increased in the phase of initial hypertrophy and the alpha-sarcomeric-actin level increased at the end of the compensation phase, while the caldesmon and the HSP-70 made it at the end of the initial hypertrophy phase.

CONCLUSIONS

Analysing our data we conclued that the determination of the caldesmon levels is the marker that better adjusts to the changes associated with partial bladder outlet obstruction in the rabbit.

HSP70 expression is increased during the day in a diurnal animal, the golden-mantled ground squirrel Spermophilus lateralis

Heat shock protein 70 (HSP70) gene expression was studied in a seasonal hibernator, the diurnal ground squirrel, Spermophilus lateralis. RNA transcripts of 2.7 and 2.9 kb hybridizing to an HSP70 cDNA were expressed in both brain and peripheral tissues of pre-hibernation euthermic animals; higher levels of expression were observed during the day than during nighttime samples. A decline in the expression of both transcripts occurred in all tissues examined during hibernation that remained low throughout the hibernation season, including the interbout euthermic periods and regardless of time of day. Quantitative comparisons showed pre-hibernation nighttime HSP70 expression to be as low as that observed during hibernation, despite the drastic increase in metabolic state and nearly 30 degrees C difference in body temperature. In contrast to HSP70, some mRNAs, such as beta-actin and HSP60, remained relatively constant, while others, such as glyceraldehyde 3-phosphate dehydrogenase, increased in specific tissues during the hibernation season. These results indicate that the expression of a highly conserved gene involved in protection from cellular stress, HSP70, can vary with an animal's arousal state.

Protein determination by ponceau S using digital color image analysis of protein spots on nitrocellulose membranes

A procedure was developed to estimate protein concentrations using color image analysis of protein spots stained with ponceau S. The method involved spotting a constant volume (2 microl) of the protein solutions on nitrocellulose paper, staining with acidic ponceau S, destaining, and air drying the paper. The image of the nitrocellulose paper was grabbed using a digital color scanner and thresholded with an optimal value to mark the area of the spot. The intensity of the color in the spot was measured in an arbitrary unit of intensity termed as inverse integrated gray value. This value showed a discernible increase with protein concentrations from 0.1 to 50 microg protein per spot (0.05-25 mg/ml). The method is simple and convenient compared to the conventional spectrophotometric procedures and allows several samples to be analyzed simultaneously. It can also be used to estimate protein concentration in the spots stained with Coomassie brilliant blue or other dyes.

Elevated stress protein in transitional cells exposed to urine from interstitial cystitis patients

BACKGROUND

It has been hypothesized that urine from interstitial cystitis (IC) patients may contain one or more toxic factors not present in "normal" urine. Bladder tissues exposed to these toxic factors could have elevated stress proteins. If this assumption is correct, stress protein levels could be a useful marker for identifying patients at risk for developing this syndrome.

METHODS

To experimentally investigate this possibility, a sensitive assay (ELISA) was used to measure levels of the 72 kDa stress protein in urothelial target cells after in vitro exposure to urine from IC patients.

RESULTS

We observed a modest 12% increase in 72 kDa stress protein in cells treated with urine from IC patients compared to cells exposed to normal urine (1.12 compared to 0.99 ng/microg extracted protein; P < 0.05). In addition, it was possible to demonstrate the 72 kDa stress protein in histologic sections obtained from mucosal biopsies of IC patients. Stress protein was located primarily in the surface urothelial cells of the mucosa.

CONCLUSIONS

These results seem to indicate that stress protein could play an important protective role at this particular site. They further suggest that IC urine is more toxic than normal urine and, in contact with underlying urothelial and deeper bladder tissue, may upregulate genes involved in stress protein responses. This may be an important concept in the etiology of IC.

Correlation of ischemia/reperfusion or partial outlet obstruction-induced spectrin proteolysis by calpain with contractile dysfunction in rabbit bladder

OBJECTIVES

In the rabbit, both experimental ischemia and partial outlet obstruction of the urinary bladder induce similar dysfunctions with regard to the contractile responses to both field (neuronal) stimulation and postsynaptic receptor stimulation. Circumstantial evidence indicates that the pathologic response to both conditions is related to two connected processes-tissue ischemia and reperfusion injury-that result in a marked increase in intracellular calcium ([Ca2+]i), followed by the activation of the Ca(2+)-dependent neutral protease calpain. Calpain activation results in the proteolysis of specific membrane proteins, including those of neuronal membranes (resulting in progressive denervation of the detrusor) and the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA), resulting in the previously reported decrease in SERCA. The current study is designed to generate direct support for the theory that both ischemia and partial outlet obstruction result in the activation of calpain.

METHODS

Separate sets of rabbits were subjected to 1 or 2 hours of ischemia, followed by reperfusion for different lengths of time, or partial outlet obstruction for different lengths of time. We determined the state of calpain activation by quantitating tissue proteolysis of alpha-spectrin by Western blot analysis. Correlative organ bath studies were conducted to observe the contractile responses of bladder strips to field stimulation and bethanechol administration.

RESULTS

(1) Sixty minutes of ischemia followed by 30 minutes of reperfusion resulted in (a) a reduction in the contractile responses to field stimulation and bethanechol (89% and 57%, respectively), and (b) a 72% decrease in native alpha-spectrin, with a concomitant 300% increase in its breakdown products (BDPs). Neither alpha-spectrin nor its BDPs had returned to control levels after 72 hours of reperfusion. (2) Twenty-four hours after the creation of a partial obstruction, alpha-spectrin BDP levels were increased 330%, then gradually fell to 130% of control levels by 14 days after obstruction. Concomitantly, the native alpha-spectrin level was decreased 74% 24 hours after obstruction and remained low through 7 days after obstruction. At 14 days after obstruction, the alpha-spectrin levels had recovered to 75% of control levels.

CONCLUSIONS

These findings suggest that Ca(2+)-dependent proteolysis of the preferred calpain substrate alpha-spectrin in urinary bladder tissues is increased significantly by both ischemia/reperfusion and partial outlet obstruction. Temporally, proteolysis precedes the reduced muscle function resulting from these pathologic conditions.

Assessment of stress gene mRNAs (HSP-27, 60 and 70) in obstructed rabbit urinary bladder using a semi-quantitative RT-PCR method

Stress proteins (HSPs) participate in the cellular response to various stresses including hyperthermia, hypoxia and injury. A previous work using northern blot analysis demonstrated increased expression of stress protein 70 (HSP-70) in rabbit bladder tissue subjected to partial outlet obstruction. In order to determine if the increased expression was specific for HSP-70 or, alternatively, indicated a generalized stress protein response, a modified quantitative RT-PCR technique was used to quantitate HSP mRNAs (HSP-27, 60, and 70) in normal and obstructed rabbit urinary bladder tissues. The results show the following: 1) The modified semi-quantitative RT-PCR is a sensitive and reproducible technique for detecting mRNA in bladder tissue. 2) Constitutive levels of HSP-27, HSP-60, and HSP-70 mRNAs were detected in control bladder tissues; the relative signal intensity was highest for HSP-70 and lowest for HSP-27. 3) A transient increase in HSP mRNAs was observed after obstruction; the mRNAs of HSP-27, 60 and 70 increased 4.3-, 5.6-, and 2.4-fold, respectively, at 24 h following obstruction, then gradually returned to control levels by the end of one week post-obstruction and remained stable up to 14 days post-obstruction. These data indicate that the modified quantitative RT-PCR is a useful technique for detecting mRNA in bladder tissue; the stress response which occurs in rabbit urinary bladder tissue following partial outlet obstruction is a general phenomenon.

Expression of stress proteins (HSP-70 and HSP-90) in the rabbit urinary bladder subjected to partial outlet obstruction

Partial obstruction of the rabbit bladder outlet induces a rapid hypertrophy characterized by increased bladder mass, increased smooth muscle content, and increased collagen deposition. In addition, partial outlet obstruction induces decreased contractile responses to both field stimulation and postsynaptic receptor stimulation. Although the morphological and contractile responses to partial outlet obstruction have been well characterized, there is little information on the cellular and molecular mechanisms of these changes. In a previous study, we demonstrated that one of the earliest genes to be expressed following partial outlet obstruction in rabbits was the gene expressing stress protein-70 (HSP-70). In order to further define the genetic and molecular basis of these responses, the expression of stress gene products HSP-70 and HSP-90 in rabbit urinary bladder subjected to partial outlet obstruction has been quantitatively evaluated by Western blot coupled with laser densitometry using anti-HSP-70 and -90 monoclonal antibodies. The data show that stress gene products HSP-70 and HSP-90 are constitutively expressed in control rabbit bladder tissue and transiently increased following partial outlet obstruction. Increased content of HSP-70 was detected at 6 hr after obstruction and reached a maximum (2.7-fold over the control level) at 24 hr. Increased HSP-90 was also detected at 6 hr but reached a maximum (4.5-fold over the control level) at 12 hr. By 7 day post-obstruction, the content of these two proteins returned to the control levels.(ABSTRACT TRUNCATED AT 250 WORDS)