Activation of cytotoxic cells by syngeneic prostate antigens in experimental autoimmune vesiculo-prostatitis

Pain in chronic prostatitis and the role of ion channels: a brief overview

BACKGROUND

Prostatitis is the third most common urologic condition affecting more than half the male population at some point in their lives. There are different categories of prostatitis, of which approximately 90% of cases can be classified under the National Institute of Health (NIH) type III category (chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS)) with no causative agents identified. CP/CPPS is associated with several symptoms, of which the most prominent being chronic pain. Despite its high incidence, pain management in patients with CP/CPPS has been poor, possibly due to the lack of understanding of aetiological factors and mechanisms underlying pain development.

METHODS

An extensive literature search of published articles on the molecular mechanisms of pain in CP/CPPS was conducted using PubMed and Google Scholar search engines (https://pubmed.ncbi.nlm.nih.gov and https://scholar.google.com). The terms used for the search were: prostatitis, pain mechanism in CP/CPPS, prostatitis pain models, acid-sensing ion channels (ASICs), transient receptor potential vanilloid type 1 (TRPVs), purinergic channels (P2X) in prostatitis pain mechanism and inflammatory mediators in CP/CPPS. The papers were identified based on the title and abstract, and after excluding the articles that did not emphasize the pain mechanism in CP/CPPS. Ninety-five articles (36 review and 59 original research papers) met our criteria and were included in the review.

RESULTS

A number of inflammatory mediator molecules and pain channels, including ASICs, transient receptor potential vanilloid channels (TRPVs) and P2Xs have been investigated for their role in prostatitis pain pathology using various animal models.

CONCLUSION

This review summarizes the pain mechanisms in CP/CPPS focusing on the inflammatory mediators, neurotransmitters, pain-transducing ion channels and small animal models developed for studying prostatitis.

Single-cell multi-omics analysis presents the landscape of peripheral blood T-cell subsets in human chronic prostatitis/chronic pelvic pain syndrome

Cumulative evidence suggests that abnormal differentiation of T lymphocytes influences the pathogenesis of chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS). Thus, understanding the immune activation landscape of CP/CPPS would be helpful for improving therapeutic strategies. Here, we utilized BD™ AbSeq to digitally quantify both the protein and mRNA expression levels in single peripheral blood T cells from two CP/CPPS patients and two healthy controls. We utilized an integrated strategy based on canonical correlation analysis of 10 000+ AbSeq profiles and identified fifteen unique T‐cell subpopulations. Notably, we found that the proportion of cluster 0 in the CP/CPPS group (30.35%) was significantly increased compared with the proportion in the healthy control group (9.38%); cluster 0 was defined as effector T cells based on differentially expressed genes/proteins. Flow cytometry assays confirmed that the proportions of effector T‐cell subpopulations, particularly central memory T cells, T helper (Th)1, Th17 and Th22 cells, in the peripheral blood mononuclear cell populations of patients with CP/CPPS were significantly increased compared with those of healthy controls (P < 0.05), further confirming that aberration of effector T cells possibly leads to or intensifies CP/CPPS. Our results provide novel insights into the underlying mechanisms of CP/CPPS, which will be beneficial for its treatment.

Immunological Mechanisms Underlying Chronic Pelvic Pain and Prostate Inflammation in Chronic Pelvic Pain Syndrome

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is the most common urologic morbidity in men younger than 50 years and is characterized by a diverse range of pain and inflammatory symptoms, both in type and severity, that involve the region of the pelvis, perineum, scrotum, rectum, testes, penis, and lower back. In most patients, pain is accompanied by inflammation in the absence of an invading infectious agent. Since CP/CPPS etiology is still not well established, available therapeutic options for patients are far from satisfactory for either physicians or patients. During the past two decades, chronic inflammation has been deeply explored as the cause of CP/CPPS. In this review article, we summarize the current knowledge regarding immunological mechanisms underlying chronic pelvic pain and prostate inflammation in CP/CPPS. Cumulative evidence obtained from both human disease and animal models indicate that several factors may trigger chronic inflammation in the form of autoimmunity against prostate, fostering chronic prostate recruitment of Th1 cells, and different other leukocytes, including mast cells, which might be the main actors in the consequent development of chronic pelvic pain. Thus, the local inflammatory milieu and the secretion of inflammatory mediators may induce neural sensitization leading to chronic pelvic pain development. Although scientific advances are encouraging, additional studies are urgently needed to establish the relationship between prostatitis development, mast cell recruitment to the prostate, and the precise mechanisms by which they would induce pelvic pain.

Histopathological classification criteria of rat model of chronic prostatitis/chronic pelvic pain syndrome

OBJECTIVE

A variety of murine models of experimental prostatitis that mimic the phenotype of human chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) have been developed. However, there is still a lack of explicit diagnosis criteria about those animal model. Our study is to establish histopathological classification criteria, which will be conducive to evaluate the animal models.

METHODS

We firstly established a rat model of experimental autoimmune prostatitis that is considered a valid model for CP/CPPS. For modelling, male Sprague-Dawley rats were immunized with autologous prostate tissue homogenate supernatant emulsified with complete Freund's adjuvant by subcutaneous injection into abdominal flank and simultaneously immunized with pertussis-diphtheria-tetanus vaccine by intraperitoneal injection. Three immunizations were administered semimonthly. At the 45th day, animals were killed, and prostate tissues were examined for morphology.

RESULTS

Histologically, the prostate tissues were characterized by lymphoproliferation, atrophy of acini, and chronic inflammatory cells infiltration in the stromal connective tissue around the acini or ducts. Finally, we built histopathological classification criteria incorporating inflammation locations (mesenchyme, glands, periglandular tissues), ranges (focal, multifocal, diffuse), and grades (grade I-IV). To verify the effectiveness and practicability of the histopathological classification criteria, we conducted the treatment study with one of the alpha blockers, tamsulosin.

CONCLUSION

The histopathological classification criteria of rat model of CP/CPPS will serve for further research of the pathogenesis and treatment strategies of the disease.

Mechanisms in prostatitis/chronic pelvic pain syndrome

PURPOSE

We reviewed the current literature on mechanisms involved in the pathogenesis of prostatitis/chronic pelvic pain syndrome (CPPS).

MATERIALS AND METHODS

A literature review for the years 1966 to 2003 was performed using the MEDLINE database of the United States National Library of Medicine.

RESULTS

National Institutes of Health categories I and II prostatitis result from identifiable prostatic infections, whereas patients with category IV are asymptomatic. The majority of symptomatic cases are category III or chronic prostatitis (CP)/CPPS. The etiology of CP/CPPS is unknown. The traditional marker of inflammation, namely white blood cells in prostatic fluids, does not correlate with the predominant symptom of pelvic pain. An imbalance toward increased proinflammatory and decreased anti-inflammatory cytokines has been implicated and a few studies have shown some correlation of this with pelvic pain. The imbalance in some men may result from polymorphisms at the cytokine loci. An autoimmune process may be involved and experimental evidence indicates that this can be under hormonal influence. Recent findings include possible defects in the androgen receptor. The prostate may not even be the source of the symptoms. Pelvic pain also correlates with the neurotrophin nerve growth factor implicated in neurogenic inflammation and central sensitization. Finally, psychological stress may produce measurable biochemical changes and influence the other processes. The role of normal prostatic bacterial flora in inciting the inflammatory response has also been reconsidered.

CONCLUSIONS

The symptoms of CP/CPPS appear to result from an interplay between psychological factors and dysfunction in the immune, neurological and endocrine systems.

Autoimmune prostatitis: state of the art

The prostate is one of the main male sex accessory glands and the target of many pathological conditions affecting men of all ages. Pathological conditions of the prostate gland range from infections, chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) of a still unknown aetiology to benign hyperplasia and cancer. CP/CPPS is one of the most prevalent diseases in the urologic clinic and affects men younger than 50 years old. A significant advance in the understanding of CP/CPPS was made when an autoimmune response against prostate antigens was revealed in a considerable number of patients. During the last 30 years, extensive work has been done regarding the development and characterization of different rodent models of experimental autoimmune prostatitis (EAP). It has been demonstrated that tolerance to prostate antigens can be disrupted in some strains of rats and mice and cellular and humoral responses to prostate antigens are elicited. A Th1 pattern has been described and the cellular response seems to be the major pathogenic mechanism involved. Immune cells infiltrate the gland and induce prostate lesions. The genetic background and hormonal imbalance are factors that could contribute to the onset of the disease in susceptible young males. Moreover, spontaneous autoimmune prostatitis could also occur with advanced age in susceptible strains. In this review, we summarize the current knowledge regarding rodent models of EAP and the immunological alterations present in CP/CPPS patients. We also discuss the reliability of these experimental approaches as genuine tools for the study of human disease.

Experimental rodent models of prostatitis: limitations and potential

Prostatitis is a polyetiological inflammation of the prostate gland in men characterized by pelvic pain, irritative voiding symptoms, and sexual dysfunction. Histologically prostatitis is characterized by poly- and mononuclear cell infiltrates (neutrophils, lymphocytes, macrophages and plasma cells) in the stromal connective tissue around the acini or ducts. Prostatitis is an important worldwide health problem in men. The pathogenesis and diagnostic criteria for the condition are obscure, with the result that the development of management programs for this condition has been hindered. Animal model(s) might be useful in elucidating mechanisms involved in the molecular pathogenesis of chronic nonbacterial prostatitis and chronic pelvic pain syndrome. Given that prostatitis might have a multifactorial etiology, several animal models with unique features may prove helpful. This review examines a number of experimental rodent models of prostatitis and evaluates their advantages and limitations.

Is benign prostatic hyperplasia (BPH) an immune inflammatory disease?

OBJECTIVES

Chronic inflammation has been documented for years in benign prostatic hyperplasia (BPH), but only now has it become evident as a major factor in disease progression. This review highlights the immunologic key features of chronic inflammation in BPH and the present interpretation of these changes in the development and progression of BPH.

RESULTS

Almost all BPH specimens show inflammatory infiltrates at histologic examination, but correlation to bacterial or other foreign antigens has not been established. Recognition of prostate secretion products by autoreactive T cells and animal models on experimental prostatitis demonstrate an autoimmune component to chronic inflammation. The infiltrate consists predominantly of chronically activated CD4(+) T lymphocytes, which are permanently recruited to prostate tissue via elevated expression of interleukin 15 (IL-15) and interferon gamma (IFN-gamma), proinflammatory cytokines produced by smooth muscle and T cells, respectively. With the appearance of infiltrates, T cell-derived cytokine production of IFN-gamma, IL-2, and transforming growth factor beta increases, the former two ultimately reaching 10-fold and the latter 2-fold higher levels in fully developed BPH than in normal prostates. As "mature" BPH nodules develop, IL-4 and IL-13 expression increases >2-fold, corresponding to a T-helper (Th)0/Th2 cytokine pattern. Dysregulation of the immune response in BPH may occur via elevated expression of proinflammatory IL-17, which stimulates a multifold production of IL-6 and IL-8, key executors of stromal growth in BPH.

CONCLUSIONS

These data strongly suggest that BPH is an immune inflammatory disease. Unravelling the specific nature of immune dysregulation may help design novel drugs with these specific targets in mind.

Prostate carcinogenesis and inflammation: emerging insights

Prostate cancer remains a significant health concern for men throughout the world. Recently, there has developed an expanding multidisciplinary body of literature suggesting a link between chronic inflammation and prostate cancer. In support of this hypothesis, population studies have found an increased relative risk of prostate cancer in men with a prior history of certain sexually transmitted infections or prostatitis. Furthermore, genetic epidemiological data have implicated germline variants of several genes associated with the immunological aspects of inflammation in modulating prostate cancer risk. The molecular pathogenesis of prostate cancer has been characterized by somatic alterations of genes involved in defenses against inflammatory damage and in tissue recovery. A novel putative prostate cancer precursor lesion, proliferative inflammatory atrophy, which shares some molecular traits with prostate intraepithelial neoplasia and prostate cancer, has been characterized. Here, we review the evidence associating chronic inflammation and prostate cancer and consider a number of animal models of prostate inflammation that should allow the elucidation of the mechanisms by which prostatic inflammation could lead to the initiation and progression of prostate cancer. These emerging insights into chronic inflammation in the etiology of prostate carcinogenesis hold the promise of spawning new diagnostic and therapeutic modalities for men with prostate cancer.

Mechanisms in prostatitis/chronic pelvic pain syndrome

PURPOSE

We reviewed the current literature on mechanisms involved in the pathogenesis of prostatitis/chronic pelvic pain syndrome (CPPS).

MATERIALS AND METHODS

A literature review for the years 1966 to 2003 was performed using the MEDLINE database of the United States National Library of Medicine.

RESULTS

National Institutes of Health categories I and II prostatitis result from identifiable prostatic infections, whereas patients with category IV are asymptomatic. The majority of symptomatic cases are category III or chronic prostatitis (CP)/CPPS. The etiology of CP/CPPS is unknown. The traditional marker of inflammation, namely white blood cells in prostatic fluids, does not correlate with the predominant symptom of pelvic pain. An imbalance toward increased proinflammatory and decreased anti-inflammatory cytokines has been implicated and a few studies have shown some correlation of this with pelvic pain. The imbalance in some men may result from polymorphisms at the cytokine loci. An autoimmune process may be involved and experimental evidence indicates that this can be under hormonal influence. Recent findings include possible defects in the androgen receptor. The prostate may not even be the source of the symptoms. Pelvic pain also correlates with the neurotrophin nerve growth factor implicated in neurogenic inflammation and central sensitization. Finally, psychological stress may produce measurable biochemical changes and influence the other processes. The role of normal prostatic bacterial flora in inciting the inflammatory response has also been reconsidered.

CONCLUSIONS

The symptoms of CP/CPPS appear to result from an interplay between psychological factors and dysfunction in the immune, neurological and endocrine systems.

Age-related alterations in inflammatory response during experimental autoimmune prostatitis

Experimental autoimmune prostatitis (EAP) is an experimental model of autoimmune disease, developed in Wistar rats against prostatic components. The 12-and 18-month-old rats with EAP show a higher cellular autoimmune response and lower humoral autoimmune response compared to 3-month-old rats. The analysis of NO(.) and O(2)(-) production by peritoneal exudate cells (PECs) resulted in a higher NO(.) and O(2)(-) production in EAP rats at all ages, compared to control animals. PECs from 12- and 18-month-old rats produced more NO(.) and less O(2)(-) than PECs from 3-month-old rats. However, lipopolysacharide (LPS) did not stimulate PECs from aged rats for NO(.) production as much as in 3-month-old rats and thus, turning out in a lower index of LPS-stimulation of PECs from aged rats, compared to 3-month-old rats. Furthermore, the mast cells number in prostates of EAP rats, especially the number of degranulated cells, was higher than in control animals, but no significant differences were found between 3- and 12-month-old control rats. In conclusion, these results show that aging affects differentially the inflammation mediators during EAP.

Non-obese diabetic (NOD) mice are genetically susceptible to experimental autoimmune prostatitis (EAP)

Rodents develop inflammatory, non-infectious, prostatitis upon autoimmuniz-ation with male accessory gland (MAG) extracts in complete Freund's adjuvant (CFA). Although there appears to be differences among strains, with respect to susceptibility to induction, specific details are not known about the genetic bases of such differences. Because NOD mice have inherited a genetic predisposition to autoimmune lesions affecting, apart from the islets of Langerhans, a large array of secretory glands such as salivary glands, thyroid, parathyroids and adrenal cortex, we selected this strain to assess the influence of inherited genes upon experimentally-induced autoimmune prostatitis (EAP). Indeed, MAG extracts injected into young NOD males in association with CFA cause a severe inflammatory reaction in the prostate, accompanied by a humoral and T cell-mediated response. NOD mice develop a more aggressive form of EAP than Wistar rats, the strain of reference used to establish the model. In NOD mice, disease begins earlier, affects 100% of the animals, does not require boosting and leads to florid infiltrates circumscribed to lateral and dorsal prostatic lobes. Immune mice develop a T cell-mediated response to MAG assessed by in vitro proliferation and accompanied by the release of IFN-gamma, whereas IL-4 is not detectable in the same culture super-natants. To assess the influence of the NOD background genes upon EAP susceptibility, we tested C57BL/6.H2(g7) mice in parallel. NOD mice are considerably more susceptible to EAP induction than congenic C57BL/6.H2(g7) mice. Both strains demonstrate a detectable humoral and cell-mediated response against MAG, but the histopathological manifestations are considerably more dramatic in NOD than in the C57BL/6.H2(g7) strain. Our results thus support the notion that NOD mice have background genes which favour severe autoimmune manifestations, irrespective of the target tissue.

Prostatein (or rat prostatic steroid binding protein) is a major autoantigen in experimental autoimmune prostatitis

Experimental autoimmune prostatitis (EAP) is a disease that could be considered an experimental model of human non-bacterial prostatitis. In this experimental model, male rats are intradermally immunized with a saline extract of male sex accessory glands (RAG) in an adequate adjuvant. The prostatitis observed in the immunized animals develops as a consequence of the immune response against RAG antigens, and the histological lesion is strikingly similar to the pattern of prostatic inflammation observed in the human disease. In this study, we purified one of the prostatic autoantigens recognized by the autoantibodies in our model. Amino acid sequence analysis identified the purified protein as prostatein or rat prostatic steroid binding protein, a member of the uteroglobin superfamily. Prostatein was recognized not only by the humoral autoimmune response, but also by the cellular autoimmune response. Certainly, the DTH response and lymph node cell proliferative assays against prostatein in immunized animals yielded positive results. Prostatein is not only the target of the autoimmune response in animals immunized with the whole extract, but also an inducing antigen of the disease. Purified prostatein, when incorporated to an adequate adjuvant, elicited cellular and humoral autoimmune response and lesion in the prostate gland. The identification of one of the target antigens in autoimmune prostatitis has provided a further refinement and characterization of our model, which could serve for a better understanding of the aetiology, pathogenesis and pathophysiology of non-bacterial prostatitis.

Experimental autoimmune prostatitis: in vivo induction of the autoimmune response to lymphocytic soluble factors. Alterations at the endocrine metabolism level

PROBLEM

In rats, immunization with male accessory gland (MAG) extract promotes experimental autoimmune vesicle prostatitis. A specific mononuclear cell-mediated immune response and prostate androgen metabolism impairment in MAG-immunized rats were observed. The possibility that lymphocytic soluble factors (SoFs) can regulate the local steroid metabolism in these rats directly was studied. We investigated whether the SoFs released by MAG-sensitized lymphocytes are capable of modifying the prostatic androgen metabolism and whether they induce histologic lesions "in vivo" when they are inoculated, carried by liposomes, into untreated rats.

METHOD OF STUDY

"In vitro" enzymatic [3H]-5 alpha-dihydrotestosterone bioconversion and histologic studies were performed with prostates from SoF-treated rats (LK rats). The obtained 3 alpha/beta-hydroxysteroid-oxidoreductase activities showed that LK rat values were significantly lower than in controls: 79.0 +/- 2.5 vs 158.7 +/- 10.2 pmol/min/mg protein, respectively (P < 0.01).

RESULTS

In the histologic studies, LK rat prostates showed focalized mononuclear infiltrates of various degrees, whereas control rats showed non-atypic modification of the gland.

CONCLUSION

These results indicate that SoFs (probably total lymphokines) contribute significantly to the pathogenesis of experimental autoimmune prostatitis, involving a biochemical relationship between immune reaction and the androgenic enzymatic inhibition in the prostate.

Time course of reactive oxygen intermediates release and histopathological findings during experimental autoimmune prostatitis development

Spontaneous and stimulated reactive oxygen intermediates (ROI) release by peritoneal exudate cells (PEC) and histopathological findings in the prostate gland were assessed during experimental autoimmune prostatitis (EAP) development. Results in EAP rats were compared with data from rats immunized with kidney homogenate, BSA, and CFA, as well as nontreated rats. At 28 days of first immunization (FI), EAP rats spontaneously released significantly more ROI than occurred in the cells from control rats. A similar response was found when ROI release was analyzed after in vitro stimulus. In time course studies, an increased spontaneous O2- production was observed at day 7 after FI, and remained the same during all period studied, (14, 21, and 28 days after FI). The stimulated O2- production showed elevated levels at 7 days after FI and fell afterward to levels similar to those of nontreated rats and increased again at 28 days. Spontaneous or stimulated H2O2 release showed a progressive increase during the study periods. ROI release was correlated with infiltrate formation in the prostate gland. This differential responsiveness could indicate that, during the autoimmune process, the autoantigen(s) amplify the inflammatory response triggered by them.

Experimental autoimmune prostatitis (EAP): enhanced release of reactive oxygen intermediates (ROI) in peritoneal macrophages

The metabolic state of peritoneal macrophages is defined quantitatively for spontaneous ROI release and compared with those produced after cell contact with phorbol myristate acetate (PMA) or zymosan (OZ) particles. Peritoneal exudate cells (PEC) from EAP animals spontaneously released significantly more ROI than cells from controls rats, indicating that mononuclear phagocytes from autoimmune rats were more activated than populations cells arising from rats injected with BSA, with CFA or non-injected. These findings could indicate an in vivo activation state in PEC from autoimmune rats different from that obtained with heterologous antigens or CFA immunization procedures. The release of ROI induced after in vitro stimulus was, in general, higher in cells from autoimmune than in BSA or CFA treated rats. This differential responsiveness between the MAG, BSA and CFA injected macrophage populations could indicate that during the autoimmune process the autoantigen/s could amplify the inflammatory response triggered by them. Although release of oxygen metabolites represents only one of many potential mechanisms of tissue injury, this together with the lesions observed in the prostate gland indicate that oxygen radicals could be involved in this autoimmune disease.