Acute inflammation promotes early cellular stimulation of the epithelial and stromal compartments of the rat prostate

Prostate immunology: A challenging puzzle

Mucosal immunity defines the relationship of surfaces in contact with the environment and integrates diverse tissues such as epidermis, gum, nose, gut, uterus and prostate with the immune system. Although considered part of a system, each mucosa presents specific immune features beyond the barrier and secretory functions. Information regarding the mucosal immunology of the male reproductive tract and the prostate gland in particular is scarce. In this review, we approach the prostate as an epithelial barrier and as part of the mucosal immune system. Finally, we also raise a series of questions that will improve the understanding of this gland, its role in reproduction and its sensitivity/resistance to disease.

Inefficient N2-Like Neutrophils Are Promoted by Androgens During Infection

Neutrophils are major effectors of acute inflammation against infection and tissue damage, with ability to adapt their phenotype according to the microenvironment. Although sex hormones regulate adaptive immune cells, which explains sex differences in immunity and infection, little information is available about the effects of androgens on neutrophils. We therefore aimed to examine neutrophil recruitment and plasticity in androgen–dependent and –independent sites under androgen manipulation. By using a bacterial model of prostate inflammation, we showed that neutrophil recruitment was higher in testosterone-treated rats, with neutrophil accumulation being positively correlated to serum levels of testosterone and associated to stronger inflammatory signs and tissue damage. Testosterone also promoted LPS-induced neutrophil recruitment to the prostate, peritoneum, and liver sinusoids, as revealed by histopathology, flow cytometry, and intravital microscopy. Strikingly, neutrophils in presence of testosterone exhibited an impaired bactericidal ability and a reduced myeloperoxidase activity. This inefficient cellular profile was accompanied by high expression of the anti-inflammatory cytokines IL10 and TGFβ1, which is compatible with the “N2-like” neutrophil phenotype previously reported in the tumor microenvironment. These data reveal an intriguing role for testosterone promoting inefficient, anti-inflammatory neutrophils that prolong bacterial inflammation, generating a pathogenic environment for several conditions. However, these immunomodulatory properties might be beneficially exploited in autoimmune and other non-bacterial diseases.

The Response of Prostate Smooth Muscle Cells to Testosterone Is Determined by the Subcellular Distribution of the Androgen Receptor

Androgen signaling in prostate smooth muscle cells (pSMCs) is critical for the maintenance of prostate homeostasis, the alterations of which are a central aspect in the development of pathological conditions. Testosterone can act through the classic androgen receptor (AR) in the cytoplasm, eliciting genomic signaling, or through different types of receptors located at the plasma membrane for nongenomic signaling. We aimed to find evidence of nongenomic testosterone-signaling mechanisms in pSMCs and their participation in cell proliferation, differentiation, and the modulation of the response to lipopolysaccharide. We demonstrated that pSMCs can respond to testosterone by a rapid activation of ERK1/2 and Akt. Furthermore, a pool of ARs localized at the cell surface of pSMCs is responsible for a nongenomic testosterone-induced increase in cell proliferation. Through membrane receptor stimulation, testosterone favors a muscle phenotype, indicated by an increase in smooth muscle markers. We also showed that the anti-inflammatory effects of testosterone, capable of attenuating lipopolysaccharide-induced proinflammatory actions, are promoted only by receptors located inside the cell. We postulate that testosterone might perform prohomeostatic effects through intracellular-initiated mechanisms by modulating cell proliferation and inflammation, whereas some pathological, hyperproliferative actions would be induced by membrane-initiated nongenomic signaling in pSMCs.

Testosterone Rescues the De-Differentiation of Smooth Muscle Cells Through Serum Response Factor/Myocardin

Prostatic smooth muscle cells (pSMCs) differentiation is a key factor for prostatic homeostasis, with androgens exerting multiple effects on these cells. Here, we demonstrated that the myodifferentiator complex Srf/Myocd is up-regulated by testosterone in a dose-dependent manner in primary cultures of rat pSMCs, which was associated to the increase in Acta2, Cnn1, and Lmod1 expressions. Blocking Srf or Myocd by siRNAs inhibited the myodifferentiator effect of testosterone. While LPS led to a dedifferentiated phenotype in pSMCs, characterized by down-regulation of Srf/Myocd and smooth muscle cell (SMC)-restricted genes, endotoxin treatment on Myocd-overexpressing cells did not result in phenotypic alterations. Testosterone at a physiological dose was able to restore the muscular phenotype by normalizing Srf/Myocd expression in inflammation-induced dedifferentiated pSMCs. Moreover, the androgen reestablished the proliferation rate and IL-6 secretion increased by LPS. These results provide novel evidence regarding the myodifferentiating role of testosterone on SMCs by modulating Srf/Myocd. Thus, androgens preserve prostatic SMC phenotype, which is essential to maintain the normal structure and function of the prostate. J. Cell. Physiol. 232: 2806-2817, 2017. © 2016 Wiley Periodicals, Inc.

Androgen regulation of host defenses and response to inflammatory stimuli in the prostate gland

The prostate gland is a strictly androgen-dependent organ which is also the main target of infectious and inflammatory diseases in the male reproductive tract. Host defenses and immunity of the gland have unique features to maintain a constant balance between response and tolerance to diverse antigens. In this context, the effects of reproductive hormones on the male tract are thus complex and have just started to be defined. From the classical description of "the prostatic antibacterial factor," many host defense proteins with potent microbicidal and anti-tumoral activities have been described in the organ. Indeed, it has been proposed a central role for resident cells, that is, epithelial and smooth muscle cells, in the prostatic response against injuries. However, these cells also represent the target of the inflammatory damage, leading to the development of a Proliferative Inflammatory Atrophy-like process in the epithelium and a myofibroblastic-like reactive stroma. Available data on androgen regulation of inflammation led to a model of the complex control, in which the final effect will depend on the tissue microenvironment, the cause of inflammation, and the levels of androgens among other factors. In this paper, we review the current scientific literature about the inflammatory process in the gland, the modulation of host defense proteins, and the influence of testosterone on the resolution of prostatitis.

Influence of E. coli-induced prostatic inflammation on expression of androgen-responsive genes and transforming growth factor beta 1 cascade genes in rats

BACKGROUND

Prostatic inflammation is reportedly associated with the development of prostatic hyperplasia. We investigated the effects of prostatic inflammation on expression levels of androgen-responsive genes and growth factors in the rat prostate.

METHODS

Prostatic inflammation was induced by Escherichia coli (strain 1677) injection (0.2 ml of 1 × 10(8) CFU/ml) into the prostatic urethra of male Sprague-Dawley rats, and ventral lobes of the prostate were harvested on day 84. Rats were given 10 mg/kg celecoxib during the last month in the COX-2 inhibitor treated group. Histopathology and multiplex enzyme-linked immunosorbent assay (ELISA) for inflammation-related proteins were performed. Glandular epithelial cells and stromal regions were separately isolated using laser-capture microdissection (LCM). Real-time RT-PCR was performed to examine mRNA levels of androgen-responsive genes in the epithelium and tumor growth factor-β1 (TGF-β1) cascade genes in the stroma.

RESULTS

Hematoxylin and eosin staining showed that mild inflammation was distributed diffusely throughout the prostate. Polymorphonuclear cells infiltrated the slightly edematous stroma, but no morphological changes were observed in the epithelium. Immunohistochemically, expression of androgen receptor and TGF-β1 in addition to IL-6 and cyclooxigenase-2 (COX-2) were enhanced in the E. coli inoculated rats. All of these factors were suppressed in the celecoxib-treated rats. Upregulation of IL-1α, IL-1β, IL-6, and RANTES in the E. coli-inoculated rats was normalized by celecoxib treatment. Significant upregulation of androgen receptor and androgen-responsive genes such as Eaf2, ELL2, FKBP5, calreticulin, and ornithine decarboxylase was observed in the LCM-dissected epithelium. Also TGF-β1 and its downstream cascade genes such as Hic-5, collagen 1, and fibronectin were upregulated significantly in the LCM-dissected stroma. The COX-2 inhibitor treatment suppressed upregulation of these genes.

CONCLUSIONS

Prostatic inflammation changed the expression of androgen-responsive genes in the epithelium and TGF-β1 cascade genes in the stroma. Activation of TGF-β1 cascade genes in the inflamed stroma, as well as altered androgen-responsive gene expression in the epithelium, might be involved in the development of BPH. Prostate 75:381-389, 2015. © 2014 Wiley Periodicals, Inc.

Upregulation of androgen-responsive genes and transforming growth factor-β1 cascade genes in a rat model of non-bacterial prostatic inflammation

BACKGROUND

Prostatic inflammation is associated with the development of prostatic hyperplasia. We investigated the effects of prostatic inflammation on expression levels of androgen-responsive genes and growth factors in the prostate.

METHODS

Prostatic inflammation was induced by formalin injection into bilateral ventral lobes of the prostate of male SD rats. After 28 days, the prostate was harvested for analyses of proinflammatory cytokines, androgen-responsive genes in the epithelium, and TGF-β1 cascade genes in the stroma. Some rats were given a COX-2 inhibitor (celecoxib; 10 mg/kg/day) by oral gavage for 28 days.

RESULTS

The formalin-injected prostate exhibited widespread low-grade inflammation (<50 leukocytes/10,000 μm(2) ) along with focal high-grade inflammation (>100 leukocytes/10,000 μm(2) ) in limited areas. Compared to control, formalin-injected prostate exhibited a 2.5-fold to sixfold increased protein expression of IL-1α, IL-1β, and IL-6. In the low-grade inflammatory regions, threefold to ninefold and twofold to threefold upregulations of mRNA levels of androgen receptors/androgen-responsive genes and TGF-β1 cascade genes were respectively, observed in the epithelium and stroma obtained by laser-capture microdissection. Positive staining for androgen receptors in the epithelial nuclei, and TGF-β1, IL-6, and COX-2 in the stroma was increased in the low-grade inflammation area. COX-2 inhibitor treatment suppressed these upregulations of cytokines, androgen-responsive, and TGF-β1 cascade genes.

CONCLUSIONS

Prostatic inflammation induced increased expression of androgen-responsive genes in the epithelium and TGF-β1 cascade genes in the stroma, which were suppressed by COX-2 inhibitors, suggesting that activation of these genes in the low-grade inflammatory region might be involved in the development of symptomatic BPH.

A mouse model of chronic prostatic inflammation using a human prostate cancer-derived isolate of Propionibacterium acnes

BACKGROUND

Prostatic inflammation has been linked to a number of prostatic diseases such as benign prostatic hyperplasia (BPH), prostatitis syndromes, and prostate cancer. Major unanswered questions include what pathogenic mechanisms, such as bacterial infections, may drive the accumulation of inflammatory infiltrates in the human prostate, and how inflammation might contribute to disease. To study this potential link in an in vivo system, we developed a mouse model of long-term bacteria-induced chronic inflammation of the prostate using a human prostatectomy-derived strain of Propionibacterium acnes.

METHODS

C57BL/6J mice were inoculated, via urethral catheterization, with vehicle control or a prostatectomy-derived strain of P. acnes (PA2). Animals were assessed at 2 days, 1, 2, or 8 weeks post-inoculation via histology and immunohistochemistry (IHC).

RESULTS

PA2 inoculation resulted in severe acute and chronic inflammation confined to the dorsal lobe of the prostate. Chronic inflammation persisted for at least 8 weeks post-inoculation. Inflammatory lesions were associated with an increase in the Ki-67 proliferative index, and diminished Nkx3.1 and androgen receptor (AR) production. Interestingly, the observed response required live bacteria and both IHC and in situ hybridization assays for P. acnes indicated a potential intracellular presence of P. acnes in prostate epithelial cells.

CONCLUSIONS

To our knowledge, this is the first mouse model of long-term prostatic inflammation induced by P. acnes, and more generally, any prostatectomy-derived bacterial isolate. This model may serve as a valuable preclinical model of chronic prostatic inflammation that can be used to mechanistically study the link between inflammation and prostatic disease.

Prostate cancer and inflammation: the evidence

Chronic inflammation is now known to contribute to several forms of human cancer, with an estimated 20% of adult cancers attributable to chronic inflammatory conditions caused by infectious agents, chronic non-infectious inflammatory diseases and/or other environmental factors. Indeed, chronic inflammation is now regarded as an 'enabling characteristic' of human cancer. The aim of this review is to summarize the current literature on the evidence for a role for chronic inflammation in prostate cancer aetiology, with a specific focus on recent advances regarding the following: (i) potential stimuli for prostatic inflammation; (ii) prostate cancer immunobiology; (iii) inflammatory pathways and cytokines in prostate cancer risk and development; (iv) proliferative inflammatory atrophy (PIA) as a risk factor lesion to prostate cancer development; and (v) the role of nutritional or other anti-inflammatory compounds in reducing prostate cancer risk.

Anti-inflammatory and antioxidant activity of thymoquinone in a rat model of acute bacterial prostatitis

Prostatitis plays a major role in morbidity and mortality related to prostate diseases. The aim of this study was to detect whether thymoquinone (TQ) could ameliorate oxidative damage and the proliferative response induced by Escherichia coli ( E. coli) in rats. A total of 42 adult male Wistar rats were used. The rats were randomly divided into seven groups (three treatment groups, three infected groups and one control group). Control group received saline and was killed 24 h after saline administration. Infected rats were killed after 24, 48 and 72 h following direct injection of E. coli into the prostate. Treatment groups were administered with 10 mg/kg dose of TQ intraperitoneally following E. coli injection and after 24 and 48 h following E. coli injection. The rats were killed at 24, 48 and 72 h after the first drug administration. Each group was compared with each other and with the control group. In addition, infected groups were compared with treatment groups. Our findings show that the treatment with TQ has a protective effect against bacterial prostatitis-induced tissue injury. Increase in malondialdehyde levels and histological damage caused by E. coli were improved markedly with TQ treatment. TQ treatment particularly increased the activity of glutathione peroxidase and decreased the activities of catalase and superoxide dismutase. These observations might be attributed, at least in part, to the antioxidant effect of TQ and suggest that it could be a clinically valuable agent in the prevention of acute prostatitis caused by E. coli.

Persistent inflammation leads to proliferative neoplasia and loss of smooth muscle cells in a prostate tumor model

In prostate cancers, epidemiological data suggest a link between prostate inflammation and subsequent cancer development, but proof for this concept in a tumor model is lacking. A constitutively active version of IκB kinase 2 (IKK2), which is activated by many inflammatory stimuli, was expressed specifically in the prostate epithelium. Constitutive activation of the IKK2/nuclear factor κB axis was insufficient for prostate transformation. However, in combination with heterozygous loss of phosphatase and tensin homolog, IKK2 activation led to an increase in tumor size, formation of cribriform structures, and increase in fiber in the fibroblastic stroma. This phenotype was coupled with persistent inflammation evoked by chemokine expression in the epithelium and stroma. The hyperplastic and dysplastic epithelia correlated with changes evoked by decreased androgen receptor activation. Conversely, inflammation correlated with stromal changes highlighted by loss of smooth muscle cells around prostate ducts. Despite the loss of the smooth muscle barrier, tumors were rarely invasive in a C57BL/6 background. Data mining revealed that smooth muscle markers are also downregulated in human prostate cancers, and loss of these markers in primary tumors is associated with subsequent metastasis. In conclusion, our data show that loss of smooth muscle and invasiveness of the tumor are not coupled in our model, with inflammation leading to increased tumor size and a dedifferentiated stroma.

Dedifferentiation of prostate smooth muscle cells in response to bacterial LPS

BACKGROUND

Prostate smooth muscle cells (SMCs) are strongly involved in the development and progression of benign prostatic hyperplasia and prostate cancer. However, their participation in prostatitis has not been completely elucidated. Thus, we aimed to characterize the response of normal SMC to bacterial lipopolysaccharide (LPS).

METHODS

Primary prostate SMCs from normal rats were stimulated with LPS (0.1, 1, or 10 µg/ml) for 24 or 48 hr. The phenotype was evaluated by electron microscopy, immunofluorescence, and Western blot of SMCα-actin (ACTA2), calponin, vimentin, and tenascin-C, while the innate immune response was assessed by immunodetection of TLR4, CD14, and nuclear NF-κB. The secretion of TNFα and IL6 was determined using ELISA.

RESULTS

Bacterial LPS induces SMCs to develop a secretory phenotype including dilated rough endoplasmic reticulum cisternae with well-developed Golgi complexes. Furthermore, SMCs displayed a decrease in ACTA2 and calponin, and an increase in vimentin levels after LPS challenge. The co-expression of ACTA2 and vimentin, together with the induction of tenascin-C expression indicate that a myofibroblastic-like phenotype was induced by the endotoxin. Moreover, LPS elicited a TLR4 increase, with a peak in NF-κB activation occurring after 10 min of treatment. Finally, LPS stimulated the secretion of IL6 and TNFα.

CONCLUSIONS

Prostate SMCs are capable of responding to LPS in vitro by dedifferentiating from a contractile to a miofibroblastic-like phenotype and secreting cytokines, with the TLR4 signaling pathway being involved in this response. In this way, prostate SMCs may contribute to the pathophysiology of inflammatory diseases by modifying the epithelial-stromal interactions.

Prostate atypia: clinical and pathological variables associated with cancer diagnosis on repeat biopsy

The clinical significance of atypical glands suspicious for malignancy (atypia) on prostate biopsy is unclear. We studied a cohort of 139 patients with atypia who underwent repeat prostate biopsy. We analyzed clinical and pathological variables that may be associated with cancer on repeat biopsy. Cancer was diagnosed in 41 (29%) of patients with atypia: 26 of 41 (66%) were Gleason 6, 20% were Gleason 7 and 7% were Gleason 8 (Gleason < 6 not reported). There were no significant associations of age, race, family history, PSA, PSA density (PSAd), number of previous biopsies or time to repeat biopsy with cancer diagnosis. In multivariate regression, histological inflammation was associated with an 85% decreased probability of cancer on repeat biopsy (odds ratio; OR 0.15; 95% confidence interval; CI 0.04-0.57; P=0.04). Radical prostatectomy was performed in 14 of 41 (34%) patients with cancer; 6 (43%) were Gleason sum ≥7, 3 (21%) were pT3a and 1 (7%) had lymph node metastases. In conclusion, inflammation was independently associated with a significantly decreased risk of cancer on repeat biopsy. However, some patients with initial atypia have higher-risk prostate cancer. Additional studies are needed to elucidate these associations.

Role of bacteria in carcinogenesis, with special reference to carcinoma of the gallbladder

Carcinoma of the gallbladder (CaGB) is the fifth commonest gastrointestinal tract cancer and is endemic in several countries. The interplay of genetic susceptibility, infections, and life style factors has been proposed to be responsible for carcinogenesis of gallbladder. Persistence of infection leading to chronic inflammation, and production of certain toxins and metabolites with carcinogenic potentials, by certain bacteria has been speculated to be involved in the transformation of the gallbladder epithelium. Therefore, any bacteria that have evolved to acquire both of the above carcinogenic mechanisms can cause cancer. Salmonella typhi has been found to be prominently associated with CaGB. Chronic typhoid carriage (persistence) and production of mediators of chronic inflammation and a genotoxic toxin (cytotoxic distending toxin, CdtB) are also known for this bacterium. Furthermore, the natural concentrating function of the gallbladder might amplify the carcinogenic effect of the mediators of carcinogenesis. In addition to S. typhi, certain species of Helicobacter (H. bilis and H. hepaticus) and Escherichia coli have also been implicated in carcinogenesis. As the isolation rate is very poor with the presently available culture techniques, the existence of bacteria in a viable but non-cultivable state is quite likely; therefore, sensitive and specific molecular techniques might reveal the etiological role of bacterial infection in gallbladder carcinogenesis. If bacteria are found to be causing cancers, then eradication of such infections might help in reducing the incidence of some cancers.