Expression of HSP70-2 gene during germ cell apoptosis in rat unilateral cryptorchid testes

Extracellular HSPs: The Potential Target for Human Disease Therapy

Heat shock proteins (HSPs) are highly conserved stress proteins known as molecular chaperones, which are considered to be cytoplasmic proteins with functions restricted to the intracellular compartment, such as the cytoplasm or cellular organelles. However, an increasing number of observations have shown that HSPs can also be released into the extracellular matrix and can play important roles in the modulation of inflammation and immune responses. Recent studies have demonstrated that extracellular HSPs (eHSPs) were involved in many human diseases, such as cancers, neurodegenerative diseases, and kidney diseases, which are all diseases that are closely linked to inflammation and immunity. In this review, we describe the types of eHSPs, discuss the mechanisms of eHSPs secretion, and then highlight their functions in the modulation of inflammation and immune responses. Finally, we take cancer as an example and discuss the possibility of targeting eHSPs for human disease therapy. A broader understanding of the function of eHSPs in development and progression of human disease is essential for developing new strategies to treat many human diseases that are critically related to inflammation and immunity.

Effect of 43 degrees treatment on expression of heat shock proteins 105, 70 and 60 in cultured monkey Sertoli cells

AIM

To examine the possible effect of heat treatment on expression of heat shock proteins (Hsps) 105, 70, and 60 in primary monkey Sertoli cells and to evaluate the possible signal pathways.

METHODS

Western blot analysis, real-time polymerase chain reaction (PCR), and confocal immunohistochemistry were used to analyze mRNA and protein levels of the Hsps in response to 43 degrees treatment of Sertoli cells isolated from pubertal monkey testes.

RESULTS

Staining with Hoechst 33342 indicated Sertoli cells did not undergo apoptosis after heat treatment. Hsp105 was expressed in cytoplasm of untreated Sertoli cells. Both Hsp105 mRNA and protein levels were increased approximately 20-fold compared to those of the untreated controls at 12 h after heat treatment. Untreated Sertoli cells did not express Hsp70, but heat stress induced its expression in the cell cytoplasm. The time-course of changes in Hsp70 was similar to that of Hsp105. In contrast to Hsp105 and Hsp70, the change in Hsp60 expression was much less obvious. The protein level between 12 h and 48 h after heat treatment was only approximately 1.5-fold that of the untreated control. Extracellular regulated kinase (ERK) 1/2 inhibitor (U0126) or phosphoinositide kinase-3 (PI3K) inhibitor (LY294002) could partially block the response of Hsp105 and Hsp70 induced by heat treatment.

CONCLUSION

These results indicate that the heat-induced expression of the three types of Hsp in monkey Sertoli cells might be regulated by ERK and/or PI3K signal pathways, but the profile of their expression is different, suggesting that they might have different regulatory functions in Sertoli cells.

Heat shock transcription factor 1 down-regulates spermatocyte-specific 70 kDa heat shock protein expression prior to the induction of apoptosis in mouse testes

Expression of constitutively active heat shock transcription factor 1 (HSF1) in mouse spermatocytes induces apoptosis and leads to male infertility. We report here that prior to the onset of massive apoptosis caused by expression of active HSF1 in spermatocytes a marked reduction in spermatocyte-specific Hsp70.2 mRNA and protein levels occurs. In addition, HSP70.2 protein relocalizes from a predominant cytoplasmic to a nuclear position in developing spermatocytes that express active HSF1. Later in the developmental stages, cells undergoing HSF1-induced apoptosis essentially lack the HSP70.2 protein. The down-regulation of Hsp70.2 gene expression by HSF1 is paradoxical because HSF1 is the prototypical activator of HSP genes. Furthermore, HSF1-mediated repression neither involved a heat shock element (HSE)-like sequence adjacent to the Hsp70.2 gene nor were Hsp70.2 promoter sequences associated directly with HSF1. Interestingly, other spermatocyte- and spermatid-specific transcripts are also down-regulated in testes of transgenic mice expressing active HSF1, suggesting involvement of a putative HSF1-dependent block of development of spermatogenic cells. Importantly however, transcription of the Hsp70.2 gene is down-regulated in testes of wild-type mice subjected to a hyperthermia that induces transient activation of HSF1, indicating that the spermatocyte-specific activity of HSF1 might misdirect a network of transcription factors required for proper regulation of Hsp70.2.

Heat treatment induces liver receptor homolog-1 expression in monkey and rat sertoli cells

We demonstrated in this study that liver receptor homolog-1 (LRH-1) was expressed in the round spermatids in normal monkey testis, and no LRH-1 signal was observed in the Sertoli cells. After local warming (43 C) the monkey testis, however, LRH-1 expression was induced in the Sertoli cells in coincidence with activation of cytokeratin 18 (CK-18), a Sertoli cell dedifferentiated marker. Furthermore, we isolated rat primary Sertoli cells from testes at various stages of development and treated with 43 C water in vitro. The changes in LRH-1 as well as CK-18 expression were analyzed by confocal immunohistochemistry and Western blot. The results showed that LRH-1 was stage-dependently expressed in the Sertoli cells; no LRH-1-positive signal was detected in the cells obtained from the testes of adult rat on d 60 after birth when mature spermatozoa in the testis was completed. However, the mature Sertoli cells were warmed at the 43 C water bath for 15 min, and the LRH-1 signal was remarkably induced in a time-dependent manner, just like the changes of CK-18 expression in the Sertoli cells, suggesting that the heat-induced dedifferentiation of the mature Sertoli cells might be related to LRH-1 regulation. LRH-1 expression induced by the heat treatment was completely inhibited by the addition of ERK inhibitor U0126 in the culture, indicating that the heat-induced LRH-1 expression in the Sertoli cells may be regulated via ERK1/2 activation pathway. Testosterone was found to have no such effect on LRH-1 expression in the monkey and rat Sertoli cells.

Expression of a K48R mutant ubiquitin protects mouse testis from cryptorchid injury and aging

Testis injury models can be useful for determining the in vivo function of genes. In this study, ubiquitin, a tag for 26S-proteasome degradation, was mutated at lysine 48 (K48R) to inhibit ubiquitin chain assembly. K48R transgenic mice had testes with delayed germ cell loss following the acute injury of experimental cryptorchidism, and were resistant to the chronic injury of aging-associated testicular atrophy. After 4 days of cryptorchid-mediated heat stress, the average weight of cryptorchid testes in wild-type ubiquitin mice was significantly lower (P < 0.05) than in K48R mutant ubiquitin mice, indicating that altered ubiquitination delayed germ cell death. Light microscopy confirmed that the testicular injury, in both wild-type and K48R ubiquitin mice, was due to germ cell death. In addition, wild-type ubiquitin mice aged 19 to 22 months showed greater testicular atrophy and decreased average seminiferous tubule diameter when compared with K48R-aged testes. These results demonstrate a resistance to testicular injury conferred by the K48R mutation, suggesting that ubiquitin-mediated protein degradation is involved in the processing or modulation of testicular insults.

Androgen aromatization in cryptorchid mouse testis

Estrogens play an important role in germ cell development. Therefore, we have studied expression patterns of aromatase that converts testosterone into estrogens in 2 recombinant inbred mouse strains that differ in efficiency of spermatogenesis. In order to show whether germ cells are a target for estrogens, estrogen receptors (ER)alpha and beta were localized as well. Adult male CBA and KE mice were made unilaterally cryptorchid to determine alterations in testicular steroidogenesis and spermatogenesis. Differences between control and cryptorchid testes have been studied with respect to (1) cellular sites of aromatase, the enzyme responsible for estrogen formation, (2) the presence of ERalpha and ERbeta in various types of testicular cells, and (3) steroidogenic activity in the testes. Additionally, unilaterally control testes of cryptorchid mice were compared with bilaterally descended testes. Histological or hormonal differences were not found between control testes of cryptorchid and untreated mice. In cryptorchid testes from both strains, degeneration of germ cells was observed as well as a decrease in size of the seminiferous tubules, whereas the amount of interstitial tissue increased, especially in testes of CBA mice. Using immunohistochemistry, aromatase was localized in Leydig cells and germ cells in both control and cryptorchid testes. Sertoli cells were immunopositive in control testes only. In cryptorchid testes of KE mice, aromatase was strongly expressed in spermatids, that were still present in a few tubules. Other cell types in tubules were negative for aromatase. In both control and cryptorchid testes of both mouse strains, ERalpha were present in Leydig cells only, whereas ERbeta were found in Leydig cells and in germ cells in early stages of maturation. In homogenates of testes of CBA control mice, testosterone levels were 3-fold higher than in those of control KE mice, whereas the difference in estradiol levels between both strains was small. Cryptorchidism resulted in decreased testosterone levels and increased estradiol levels. The results of the present study show functional alterations due to cryptorchidism in both mouse strains. Strong aromatase expression in germ cells in control and cryptorchid testes indicates an additional source of estrogens in the testis besides the interstitial tissue and the relevance of estrogen in spermatogenesis.

Abdominal temperature induces region-specific p53-independent apoptosis in the cauda epididymidis of the mouse

It is widely accepted that temperature regulates gene expression and function in the epididymis. However, the significance of reduced temperature of the scrotum in cell survival had not often been examined. Our hypothesis was that the experimental increase of the temperature could induce apoptosis. Using a surgical method that consists of surgically reflecting the cauda epididymidis in the abdomen, we have been able to show that this is the case. Apoptosis was examined by histologic procedures and by visualization of DNA fragmentation in agarose gels. We determined that the apoptosis is region-specific and affects only the principal cells of the proximal region of the cauda. It starts 12 h after surgery and ends by the third day. The apoptotic cells are eliminated by extrusion into the lumen and phagocytosis by adjacent cells. The complete molecular mechanism of apoptosis in this case remains unknown, but we have used the techniques of immunocytochemistry, Western blot, and reverse transcription-polymerase chain reaction to determine the role of some molecules. We have seen no significant role of androgens, the tumor suppressor p53, nor two heat shock proteins, hsp-25 and hsp-70. Nevertheless, we have detected a strong induction of bax and bcl-2 gene products. While the former should be responsible for the apoptosis observed, the latter would promote the survival of most of the cells of the cauda epididymis.

Cloning and characterization of temperature-related gene TRS1

To investigate the mechanism of spermatogenesis arrest derived from heat treatment and to screen temperature-related genes involved in spermatogenesis, the authors analyzed the differences in gene expression between cryptorchid and scrotal testes in rats, and cloned a full-length cDNA named TRS1. In situ hybridization showed that TRS1 mRNA was mainly expressed in spermatocyte and round spermatids in testis. The expression level decreased in cryptorchid testis, suggesting that the lower scrotal temperature is a key factor in keeping the normal expression of TRS1. At the N-terminal of TRS1, there was a plecstrin homology (PH) domain signature. This PH domain has high similarity to that in PEPP2, a homosapien protein, which has a characteristic of binding phosphatidylinositol 3-phosphate via its PH domain in vitro. These findings suggest that TRS1 may be important in spermatogenesis and give clues for further research on the function of TRS1.

Expression of P16(INK4a) in testis of rhesus monkey during heat stress and testosterone undecanoate induced azoospermia or oligozoospermia

Previous studies on azoospermia or oligozoospermia induced by heat stress or high doses of testosterone mainly focused on germ cell apoptosis; no data regarding their possible effect on spermatogonia mitosis are available. We have established unilateral cryptorchid and testosterone undecanoate (TU)-treated monkey models and examined expression of P16(INK4a) in the testis to look at its possible role in azoospermia or oligozoospermia induced by the heat stress or the TU treatment. The results showed that both heat stress and TU were capable of inducing expression of P16(INK4a) mainly in spermatogonia and other types of germ cells as well as Sertoli cells at the later stage of germ cell apoptosis, namely on Day 10 after operation or on Day 60 after TU injection. It is, therefore, suggested for the first time that P16(INK4a) protein may inhibit the spermatogonia mitosis in the testis at the later stage of the germ cell apoptosis, resulting in arrest of spermatogenesis.

Expression of Hsp70-2 in unilateral cryptorchid testis of rhesus monkey during germ cell apoptosis

We investigated the possible role of Hsp70-2 in germ cell apoptosis induced by heat stress in monkey unilateral cryptorchid testis. The study focused on in situ analysis of the testicular cell DNA fragmentation and on the possible relationship between Hsp70-2 expression and germ cell apoptosis. The TUNEL result showed that most of the germ cells were labeled in the cryptorchid testis on d 5 after induction of cryptorchidism; that with most of the apoptotic germ cells depleted, only a few germ cells were labeled on d 10; and that almost no apoptotic signal was observed in the cryptorchid testis on d 15 and thereafter. This indicates that the increasing germ cell degeneration in cryptorchid testis may take the form of apoptosis. Using in situ hybridization, immunohistochemistry, and Northern blot, we examined the changes of Hsp70-2 expression in the monkey cryptorchid testis. The level of Hsp70-2 mRNA decreased slightly, while the expression of HSP70-2 protein was almost unchanged at the early stage of germ cell apoptosis in the cryptorchid testis on d 5 and dropped dramatically along with the loss of apoptotic germ cells in the cryptorchid testis on d 10 after operation. It is therefore suggested that Hsp70-2 might not take part in inhibiting the apoptosis of germ cells at the early stage during operation-induced cryptorchid testis, and that Hsp70-2 gene does not belong to the immediate early related gene responsible for germ cell apoptosis induced by heat stress.