Inflammasomes are important mediators of prostatic inflammation associated with BPH

Abstract

Background
There is mounting evidence to support the role of inflammation in benign prostate hyperplasia (BPH), and a recent study reported expression of inflammasome derived cytokine IL-18 in prostate biopsy of BPH patients. Here we examined the expression of inflammasome-derived cytokines and activation of nucleotide-binding oligomerization domain-like receptor with pyrin domain protein 1 (NLRP) 1 inflammasome in a rat model of prostatic inflammation relevant to BPH.

Methods
Prostatic inflammation was experimentally induced in three-month-old male Sprague–Dawley rats by intraprostatic injection (50 μL) of either 5 % formalin or saline (sham) into the ventral lobes of prostate. 7 days later, prostate and bladder tissue was harvested for analysis of inflammasome by Western blot, immunohistochemistry and downstream cytokine production by Milliplex.

Results
Expression of interleukins, CXC and CC chemokines were elevated 2-15 fold in formalin injected prostate relative to sham. Significant expression of NLRP1 inflammasome components and caspase-1 in prostate were associated with significant elevation of pro and cleaved forms of IL-1β (25.50 ± 1.16 vs 3.05 ± 0.65 pg/mg of protein) and IL-18 (1646.15 ± 182.61 vs 304.67 ± 103.95 pg/mg of protein). Relative to prostate tissue, the cytokine expression in bladder tissue was much lower and did not involve inflammasome activation.

Conclusions
Significant upregulation of NLRP1, caspase-1 and downstream cytokines (IL-18 and IL-1β) suggests that a NLRP1 inflammasome is assembled and activated in prostate tissue of this rat model. Recapitulation of findings from human BPH specimens suggests that the inflammasome may perpetuate the inflammatory state associated with BPH. Further clarification of these pathways may offer innovative therapeutic targets for BPH-related inflammation.

Full text

R E S E A R C H Open Access
Inflammasomes are important mediators of
prostatic inflammation associated with BPH
Mahendra Kashyap, Subrata Pore, Zhou Wang, Jeffrey Gingrich, Naoki Yoshimura and Pradeep Tyagi
*
Abstract
Background: There is mounting evidence to support the role of inflammation in benign prostate hyperplasia (BPH),
and a recent study reported expression of inflammasome derived cytokine IL-18 in prostate biopsy of BPH patients.
Here we examined the expression of inflammasome-derived cytokines and activation of nucleotide-binding
oligomerization domain-like receptor with pyrin domain protein 1 (NLRP) 1 inflammasome in a rat model of prostatic
inflammation relevant to BPH.
Methods: Prostatic inflammation was experimentally induced in three-month-old male Sprague–Dawley rats by
intraprostatic injection (50 μL) of either 5 % formalin or saline (sham) into the ventral lobes of prostate. 7 days later,
prostate and bladder tissue was harvested for analysis of inflammasome by Western blot, immunohistochemistry
and downstream cytokine production by Milliplex.
Results: Expression of interleukins, CXC and CC chemokines were elevated 2-15 fold in formalin injected prostate relative
to sham. Significant expression of NLRP1 inflammasome components and caspase-1 in prostate were associated
with significant elevation of pro and cleaved forms of IL-1β(25.50 ± 1.16 vs 3.05 ± 0.65 pg/mg of protein) and IL-18
(1646.15 ± 182.61 vs 304.67 ± 103.95 pg/mg of protein). Relative to prostate tissue, the cytokine expression in bladder
tissue was much lower and did not involve inflammasome activation.
Conclusions: Significant upregulation of NLRP1, caspase-1 and downstream cytokines (IL-18 and IL-1β)suggeststhata
NLRP1 inflammasome is assembled and activated in prostate tissue of this rat model.Recapitulation of findings from
human BPH specimens suggests that the inflammasome may perpetuate the inflammatory state associated with BPH.
Further clarification of these pathways may offer innovative therapeutic targets for BPH-related inflammation.
Keywords: Inflammasome, NLRP1, BPH, IL-18, Chemokines
Introduction
The prevalence of benign prostatic hyperplasia (BPH)/
lower urinary tract symptoms (LUTS) in US population
is expected to increase with an ageing population and an
increased prevalence of metabolic diseases [1]. Although
generally thought to be due to prostatic enlargement,
BPH/LUTS is also known to be associated with intra-
prostatic infiltration of inflammatory cells in majority of
patients [2]. The presence of inflammatory infiltrates in
the prostate biopsy predicted unfavorable outcomes in
placebo-treated BPH patients in Medical Therapy Of
Prostatic Symptoms MTOPS study [2].
Findings from large clinical studies suggest that
LUTS, especially storage symptoms such as urgency
and frequency, associated withBPHarenotonlyacon-
sequence of bladder outlet obstruction caused by pros-
tatic enlargement, but there is also a contribution of
prostatic inflammation. A large Olmsted county study
on BPH patients found that daily use of a non-steroidal
anti-inflammatory drug was inversely associated with
onset of moderate/severe urinary symptoms [3]. Several
other epidemiologic studies have also identified obesity
as an important risk factor for BPH associated inflam-
mation and most obesity related disorders are associ-
ated with excessive inflammasome activation [4]. While
the expression of IL-1βand IL-18 were shown to be el-
evated in the prostate biopsy tissue obtained from BPH
patients [5], none of the studies so far has examined
whether this expression in the prostate is associated
with inflammasome activation.
* Correspondence: prt18@pitt.edu
Department of Urology, University of Pittsburgh, Pittsburgh, USA
© 2015 Kashyap et al.; licensee BioMed Central. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain
Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article,
unless otherwise stated.
Kashyap et al. Journal of Inflammation (2015) 12:37
DOI 10.1186/s12950-015-0082-3

Inflammasomes are cytosolic oligomeric signaling plat-
forms found in myeloid cells such as monocytes, macro-
phages and epithelial cells. Inflammasomes are thought to
be responsible for initiating an inflammatory cascade in
response to endogenous or exogenous stress signals [6]. In
particular, NLRP (NLR family containing pyrin domain)
inflammasomes are functional cytosolic homologs of mem-
brane bound toll-like receptors [6] and crucial initiators of
sterile inflammation in several metabolic disorders [7] and
chronic inflammatory diseases [8, 9]. Interestingly, a recent
report demonstrated that expression of mRNA coding for
inflammasome components [10] was higher in prostate
biopsy of BPH patients relative to the expression in prostate
cancer patients. We have previously reported on a rat
model of prostatic inflammation induced by intraprostatic
formalin injection and its relevance for BPH studies [11]. In
this study, we evaluated the expression of different chemo-
kines including the activation of the inflammasome in pros-
tate and bladder tissue following the induction of prostatic
inflammation.
Methods
All animal experiments were performed in accordance
with institutional guidelines and with an approval from
the University of Pittsburgh Institutional Animal Care and
Use Committee (Protocol # 1011435). Male Sprague–
Dawley rats weighing 250-320 g were anesthetized with
isoflurane. Following an abdominal incision, formalin (5 %
in saline) or saline (sham) was injected into each ventral
lobe of the prostate (50 μl per lobe) to produce chemically
induced prostatic inflammation. Ventral lobes of the pros-
tate and bladder tissue were excised 7 days after injection.
Histological analyses
A part of the prostate injected with either formalin or
saline (n= 3 per group) was embedded in OCT Tissue-
Tek compound (Sakura Finetek U.S.A, Torrance, CA),
frozen on dry ice, and kept at -80 °C until use. Samples
were serially sectioned at 8 μm thickness and stained
with hematoxylin and eosin.
Immuno-histochemical analysis
8μm cryosections were washed in PBS and fixed in
chilled acetone for 10 min at 4 °C. Sections were then
incubated with PBS containing 0.4 % Triton X-100
(PBST) and 5 % normal donkey serum (Jackson Immu-
noresearch) for 30 min at room temperature. The pri-
mary antibodies specific to NALP1 (1:200, Abcam); and
IL-18 (1:50, Santa Cruz Biotechnologies) were applied
overnight to sections in PBST containing 5 % normal
donkey serum at 4 °C. Sections were then washed 3
times with PBST containing 1.0 % BSA for 5 min at
room temperature and then incubated for 2 h with sec-
ondary donkey anti-primary Alexa Fluor 488 or Alexa
Flour 594 antibody (1: 200, Molecular Probes) at room
temperature. Sections were washed again for three times
at room temperature in PBST containing 1.0 % serum,
and then mounted with medium containing 4’,6-diami-
dino-2-phenylindole DAPI (Floromount-G with DAPI,
Fischer Scientific). Sections were visualized under Olympus
BX51 microscope and the images were captured using
MagnaFire 2.1 software.
Measurement of chemokines
Theprostateandbladdertissuesofratsinjectedwithfor-
malin or saline (n= 6 per group) were homogenized using
cold CelLytic™MT Mammalian Tissue Lysis/Extraction
Reagent (sigma) containing 2 mM sodium orthovanadate,
1 mM PMSF and protein cocktail inhibitor (1X, Sigma).
The homogenate was centrifuged at 10,000 rpm for 10 min
and the resulting supernatants were stored at -80 °C until
assayed. 28 proteins including interleukins IL-1α,IL-1β,
IL-2, IL-4, IL-5, IL-6, IL-10, IL-12p70, IL-13, IL-17A and
IL-18; CXC chemokines (CXCL1, CXCL2, CXCL5 and
CXCL10), CC chemokines (CCL2, CCL3, CCL5); Growth
factors NGF, BDNF, VEGF and G-CSF, other inflammatory
mediators such as eotaxin, leptin, IFN-γand TNFαlevels
were determined on a Luminex 100 using a MILLIPLEX
MAP Rat Cytokine/Chemokine Panel (Millipore, Billerica,
MA). Levels of NGF and BDNF were determined using in-
dividual ELISA kits procured from Promega, USA. Protein
estimation was done by BCA Protein Assay Kit (Pierce,
Rockford, Illinois) to standardize the chemokine concentra-
tions relative to tissue protein levels, which are expressed as
pg/mg of total protein [12].
Western blot analysis
Tissue was homogenized using CelLytic™MT Mammalian
Tissue Lysis/Extraction Reagent (Catalog no. C3228, Sigma,
USA) in the presence of phenylmethylsulfonyl fluoride
(1 mM), sodium orthovanadate(2mM)andproteininhibi-
tor cocktail (Catalog no. P8340-5ML, Sigma, USA). Protein
estimation was done by Coomassie (Bradford) Protein
Assay Kit (Thermo Scientific, USA). The lysates from the
sham and formalin injected groups were separated on
Tricine-SDS PAGE. Protein lysates (40 μg) were electro-
phoresed using 10 % Tricine-SDS Gel and then blotted
onto immobilion-P membranes (Millipore) using wet
transfer system. After blocking for 1 h at 37 °C, the
membranes were incubated overnight at 4 °C with pri-
mary antibodies specific for NALP1 (1:500, Abcam),
Caspase-1 (1; 500), IL1β(1:400) and β-Actin (1:1000, Santa
Cruz Biotechnology), in blocking buffer (pH 7.5). The
membranes were then re-incubated for 2 h at room
temperature with secondary anti-primary immunoglobulin
G (IgG)-conjugated with horseradish peroxidase (Santa
Cruz Biotechnologies, USA). Subsequently, blots were
developed using SuperSignal West Femto Maximum
Kashyap et al. Journal of Inflammation (2015) 12:37 Page 2 of 8

Sensitivity Substrate (catalog no. 34096, Thermo Scien-
tific, USA) on Versa doc imaging system (Model 4000;
BioRed, USA). Densitometry for measuring the band
specific for each protein was performed using AlphaEase
FC StandAlone V. 4.0.0 software. β-Actin was used as an
internal control to normalize the data.
Statistics
The unpaired Student’st-test was used for comparing the
values of two groups. All tests were two-sided, and p values
< 0.05 were considered statistically significant. All statistical
analyses were performed using Graphpad Prism IV.
Results
Chemokine expression in prostate & bladder
Expression of chemokines was elevated several fold in
formalin injected prostate tissue relative to the expres-
sion of respective chemokines in saline injected prostate
tissue (sham). All the chemokines belonging to CXC fam-
ily were significantly upregulated in formalin injected
prostate, with the maximum upregulation of 15 fold in
mean levels of CXCL-1 followed by 5 fold upregulation of
both CXCL-5 and CXCL-10 (Fig. 1a). Among CC chemo-
kines, CCL3 showed a 9 fold upregulation, followed by a 5
fold upregulation for CCL5 and then 2-fold upregulation
a
b
Fig. 1 aCytokine expression was elevated in prostate tissue harvested from prostatic inflammation group relative to sham. Relative to other cytokines,
expression of IL-18 was quantitatively higher and also significantly relative to the expression of IL-18 in sham prostate. There was significant upregulation of
IL-1α,IL-1β, IL-5, IL-17A, leptin, NGF, VEGF, CXC and CC chemokines (*p < 0.05, unpaired ttest) in formalin injected prostate, while expression of BDNF, IFNγ,
G-CSF, IL-2, IL-4, IL-10, IL-12p70, IL-13, TNFαremained unchanged between the groups. bOverall, expression of cytokines in bladder was lower relative to
prostate (same y-axis scale). Bladder from sham group showed significantly lower expression of IFNγ, CXCL-2, CXCL-10, CCL5, IL-5 and IL-17A compared to
the group injected with formalin (*p <0.05, unpaired ttest)
Kashyap et al. Journal of Inflammation (2015) 12:37 Page 3 of 8

for CCL2 (*p < 0.05, unpaired ttest). IL-18 expression was
quantitatively higher relative to other cytokines/chemokines
and the elevation of IL-8 in formalin injected prostate tissue
was also significant relative to sham prostate tissue.
Among other interleukins, IL-1α, IL-1β, IL-5, and
IL-17A were also significantly upregulated in formalin
prostate, with the highest fold change noted for IL-1β.
Among growth factors, prostatic inflammation induced a
significant 3 fold upregulation of VEGF, NGF and two
fold upregulation of leptin expression. The expression of
BDNF, interferon-γ(IFNγ), G-CSF, IL-2, IL-4, IL-10,
IL-12p70, IL-13, TNFαremained unchanged between
the sham and formalin injected groups, whereas the
expression of eotaxin was undetectable in prostate and
bladder tissue of both groups.
Overall, bladder tissue expression of cytokines was
lower relative to prostate of each group. Bladder tissue
obtained from rat group given intraprostatic injection of
formalin showed significantly higher expression of IFNγ,
CXCL-2, CXCL-10, CCL5, IL-5 and IL-17A (*p < 0.05,
unpaired ttest). (Fig. 1b). The expression of all other
proteins was not statistically different in the bladder
tissue of the two groups.
Western blot of inflammasome components
Western blots of prostate tissue lysate showed signifi-
cantly stronger density bands for NLRP1 (0.92 ± 0.02 vs
0.45 ± 0.01; *p < 0.05), Caspase-1 (0.97 ± 0.08 vs 0.42 ±
0.03;*p < 0.05) and mature IL-1β(0.40 ± 0.11 vs 0.08 ±
0.01;*p < 0.05) in rat group given intraprostatic injection
of formalin relative to sham prostate (Fig. 2). In contrast,
Western blot results for bladder showed absence of any
change in expression of NLRP1 and other components
following intraprostatic injection of formalin or saline.
Immuno-histochemistry of inflammasome components
Prostate from the formalin injected group showed higher
green immunoreactivity for NLRP1 and red immunore-
activity for IL-18 protein relative to the sham group
injected with the saline (Fig. 3a-f ). The yellow signal
seen in the merged image of panel F indicated the co-
localized expression of NLRP1 with IL-18 against the
blue DAPI background in the formalin injected prostate
tissue. The merged image for the sham prostate tissue in
panel E shows absence of the yellow signal, which con-
firms the lowered expression of NLRP1 and IL-18.
In contrast, there was no difference in the green immu-
noreactivity for NLRP1 and red immunoreactivity for
IL-18 in the bladder obtained from sham (Fig. 3g, i and k)
and formalin injected groups (Fig. 3h, j and l). The anti-
body for IL-18 performed better in immunohistochemistry
than in Western blot (data not shown). Therefore, a role
for inflammasome dependent cytokine expression is indi-
cated in prostate tissue, but not in bladder tissue.
Histology
Prostate tissue obtained from the sham group showed
regular shaped acini with an intact basement membrane
(Fig. 4a and c). In contrast, formalin injected prostate
tissue showed hyperplastic acini lined by tall columnar
epithelium. Epithelial pilling with budding into surround-
ing expanded stromal areas was seen in multiple foci. Infil-
tration of inflammatory cells in the formalin injected
prostate is indicated by the red color * (Fig. 4b and d).
Bladder tissue from the sham group (Fig. 4e) showed
histology similar to a normal, untreated rat. In contrast,
bladder tissue from (Fig. 4f) the formalin injected group
showed mild edematous changes, which were not accom-
panied by any marked infiltration of inflammatory cells.
Prostate
Sham Prostatic
Inflammation
Bladder
NLRP1, 155 KDa
CASP1, 55 KDa
Sham Prostatic
Inflammation
Fig. 2 Western blot analysis for components of inflammasome in prostate and bladder tissue obtained from sham and prostatic inflammation
group. Blots represent the activity of NLRP1, Caspase-1, parent and mature cleaved IL-1βin both tissues
Kashyap et al. Journal of Inflammation (2015) 12:37 Page 4 of 8

Discussion
Our previous study reported that clinical features, bio-
chemical and histological changes in formalin induced
non-infectious prostatic inflammation are highly similar
to those reported for clinical BPH [11]. In the present
study, we assessed the functional significance of inflam-
masome activation in the tissue specific expression of
cytokines/chemokine in the prostate and bladder tissues
of the same model. We observed that intraprostatic for-
malin injection leads to the assembly and activation of
NLRP1 inflammasomes in prostate and production of
pro-inflammatory cytokines, IL-1βand IL-18 following
the auto-proteolytic maturation of cysteine protease,
caspase-1. Meanwhile, the absence of inflammasome
derived products in bladder suggests that chemokine
expression in the bladder is induced by a stimulus,
which is different from the prostate.
A role for NLRP1 inflammasome in prostate tissue has
been previously demonstrated in another model of prostatic
inflammation [13] induced by intraprostatic injection of
carrageenan. Consideration of our findings, together with
other similar reports, led us to propose that Nod-like recep-
tor protein 1 (NALP1/NLRP1) inflammasomes mediate the
prostatic inflammation in response to irritable stimuli such
as formalin or carrageenan. Interestingly, detailed metabolic
and molecular phenotyping in clinical studies have indi-
cated that, inflammasome is a crucial link between BPH
and metabolic disorders [10], since the inflammasome
controls the energy expenditure and adipogenic gene ex-
pression [7] including that of adipocyte hormone leptin
[14]. Enhanced leptin production noted in prostate after
intraprostatic formalin injection mimics the likely endo-
crine influence from obesity in prostatic inflammation.
Visceral adiposity is correlated with circulating levels
of pro-inflammatory cytokines, and adipose tissue is
known to propagate inflammation locally and systemic-
ally, in part through chemokine mediated recruitment
of macrophages. Expectedly, chemokines chemotactic
for macrophages such as CCL2 were found elevated in
prostatic fluids of BPH patients [15]. The upregulated
expression of other CC chemokines, CCL2, CCL3 and
CCL5 noted in formalin injected prostate is consist-
ent with the prostatic infiltration of macrophages
[16, 14]. Macrophages not only release CCL3 but,
also serve as a site for inflammasome activation and
are also known to positively regulate gene expression
abgh
cd i j
efkl
Fig. 3 a-f Detection of NLRP1 inflammasomes (green) and derived cytokine IL-18 (red) in the prostate by immunohistochemistry in prostate of
sham (panel a, c and e) and formalin injected group (panel b, d and f). Merged image in panel F shows the co-localized expression of NLRP1
with IL-8 against the DAPI blue background in formalin injected prostate and its marked absence in sham prostate. g-l Detection of NLRP1
inflammasomes (green) and derived cytokine IL-18 (red) by immunohistochemistry in bladder of sham (panel g, i and k) and formalin injected group
(panel h, j and l). Merged image shows the constitutive expression of IL-18 against the DAPI blue background, but the absence of NLRP1 in bladder
Kashyap et al. Journal of Inflammation (2015) 12:37 Page 5 of 8

of CCL5 via NF-κB signaling cascades induced by IFN-γ
[16, 14].
Inflamed regions in prostate biopsy of BPH patients
are known to express upto 5-fold higher IFN-γcom-
pared to the non-inflamed regions [17]. Here, we found
that IFN-γinducible chemokines [18] were upregulated
to different extents in formalin-injected prostate tissue.
CXC chemokines including CXCL1, CXCL2, CXCL5, are
potent chemoattractants for neutrophils and can further
drive the neutrophil dependent tissue injury [8] visual-
ized on the histology of formalin injected prostate tissue.
CXCL2 induces migration of hematopoietic stem cells
and its expression is affected by FGF-2, which is impli-
cated in BPH [19]. CXCL-10 is chemotactic for lympho-
cytes and is structurally and functionally different from
CXCL-1, a rat homolog of human IL-8 [20].
The dysfunctional voiding reported in rats after intra-
prostatic formalin injection [21] is presumably linked
to the predominant expression of IFN-γand the IFN-γ
inducible expression of chemokine, CXCL-10 in bladder.
CXCL-10 is considered to be constitutivelyexpressedin
neurons and contribute to the excitability of primary
afferent neurons through transactivation of transient
receptor channels and nociceptor sensitization [22].
Clinical relevance of CXCL-10 in bladder function and
urinary symptoms can be gleaned from the upregulated
gene expression of CXCL-10 in bladder biopsy of
ulcerative cystitis patients [23]. Interestingly, a previous
report showed that systemic neutralization of CXCL-10
by monoclonal antibodies ameliorated the dysfunctional
voiding following chemically induced cystitis [24].
Increased expression of CXCL-10 in bladder tissue of
formalin injected rats accompanied a modest increase
in the expression of CXCL-2, CCL5, IL-5 and IL-17A,
which suggests a role for T-helper17 lymphocytes and
epithelium in the observed bladder expression of che-
mokines [17]. Ubiquitous expression of IL-18 by most
epithelial tissues [25] may explain the substantial IL-18
Fig. 4 a-d Prostate tissue sections from sham group (panel aand c) showed regular shaped acini with an intact basement membrane. Prostatic
inflammation in formalin injected group (panel band d) caused epithelial pilling with budding into surrounding stroma at multiple foci.
Expanded stromal area in formalin injected group showed inflammatory cells indicated by red colored * (panel band d). Magnification in panel
aand bis 10X and the region shown in white dotted line square region of panel a (sham) & b (prostatic inflammation) is magnified upto 4 fold
and shown in panel c & d, respectively. e-f Bladder tissue sections obtained from sham group (panel e) showed no histological changes, whereas
bladder from rat group with prostatic inflammation (panel f) showed slight edematous changes related to cytokine expression shown in Fig. 1b.
Magnification is 20X in both panels
Kashyap et al. Journal of Inflammation (2015) 12:37 Page 6 of 8

expression in bladder of both saline and formalin
injected group.
Over expression of CC and CXC chemokines in prostate
of formalin injected rats corroborates similar findings
obtained in another rat model of BPH induced by chronic
estradiol injection [26]. An earlier study mixed a colored
dye with formalin during intraprostatic injection in order to
check the spread of formalin outside of prostate tissue by
the external spread of dye [21]. The study did not find any
spread of the injected dye outside of the prostate, which
precludes a possible direct irritation of bladder by formalin
in this model. A severe inflammatory response typically
seen with direct irritation of bladder by formalin [27] was
also not seen in bladder histology images (Fig. 4f). Taking
histology images of bladder together with NLRP1 blot and
immunoreactivity indicates that inflammasome is not
assembled in bladder tissue following intraprostatic
injection of formalin. It is known that expression of
NLRP3 is higher than expression of NLRP1 in bladder
[6], but they both generate similar inflammasome
derived products. Therefore, lack of any change in the
expression of cleaved IL-1βor IL-18 in bladder tissue,
lend further support to the absence of the inflamma-
some in the bladder of this model.
NLRP1 are known to respond to endogenous meta-
bolic stress (ATP and fatty acids) [7], and to exogenous
stress of microbial infection [6], but the precise stimulus
triggering the activation of NLRP1 in human prostate
remains to be investigated. Recent studies on tissue
specimens of BPH patients have implicated a pivotal
functional role for IL-18 in BPH [5]. Predominant
expression of IL-18 in rat prostate of this model is sup-
ported by Western blot and immunoreactivity findings.
The autocrine/paracrine actions of IL-1βsecreted by
the inflammasome are implicated by the overexpression
of CC and CXC chemokines [28] in this model, as these
mediators do not require inflammasome processing for
secretion.
CC and CXC chemokines represent a large family of
chemotactic peptides with a broad range of cellular targets
generated by stromal and epithelial tissues of prostate and
bladder. Leukocyte infiltration is the primary event in in-
flammation and expression of chemokines temporally pre-
cedes that infiltration, [29] which makes them well suited
for characterizing disease phenotypes [30]. Here, we found
organ-specific prominent molecular signatures of prostatic
inflammation. Considering that NALP1/NLRP1 is a
susceptibility gene involved in the devolvement of chronic
inflammatory diseases [9], this model can be used to
understand cellular triggers of inflammasome activation in
BPH. Taken together, it is clear that the inflammasomes
plays a role in prostatic inflammation associated with BPH
and inflammasome targeted therapies could be an option
for BPH management.
Conclusions
Significant upregulation of NLRP1, caspase and down-
stream cytokines suggest that a NLRP1 inflammasome is
assembled and activated in the prostate tissue of this rat
model.Recapitulation of findings from human BPH
specimens suggests that the inflammasome may per-
petuate the inflammatory state associated with BPH and
further clarification of the pathways may offer innovative
therapeutic targets in BPH.
Abbreviations
NLRP1: Nucleotide-binding oligomerization domain-like receptor with pyrin
domain protein 1; BPH: Benign prostatic hyperplasia; IL: Interleukins;
MTOPS: Medical therapy of prostatic symptoms; LUTS: Lower urinary tract
symptoms; NGF: Nerve growth factor; BDNF: Brain derived neurotrophic
factor; VEGF: Vascular endothelial growth factor; G-CSF: Granulocyte
stimulating factor; IFN-γ: Interferon-γ.
Competing interests
The authors declare that they have no competing interests.
Authors’contributions
MK, SP, PT drafted the manuscript. ZW, JG, NY, PT conceived of the study,
and participated in its design and coordination and helped to draft the
manuscript. MK, SP, PT performed the animal experiments, immunoassays,
blots and staining. All authors read and approved the final manuscript.
Acknowledgement
The work was partly supported by grants from NIH NIDDK 2P20 DK090919
and DK088836.
Received: 30 March 2015 Accepted: 8 May 2015
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