The NACHT, LRR and PYD Domains-Containing Protein 3 (NLRP3) Inflammasome Mediates Inflammation and Voiding Dysfunction in a Lipopolysaccharide-Induced Rat Model of Cystitis.

OBJECTIVE: NOD-like receptors (NLRs) sense sterile and non-sterile signals and form inflammasomes which trigger an inflammatory response through the activation of caspase-1 and release of IL-1ß. Recently we have shown the presence of several NLRs in the bladder urothelia and demonstrated the importance of NLRP3 in bladder outlet obstruction and cyclophosphamide-induced cystitis, both models of sterile inflammation. In this study we explore a role for NLRP3 in mediating the response to LPS, a key antigen of uropathogenic bacteria. METHOD: In order to bypass the protective glycosaminoglycan layer lining the urothelium, LPS was directly injected into the bladder wall of Sprague-Dawley rats. Glyburide (a NLRP3 inhibitor) or vehicle was administered orally prior to and after injection. Rats were analyzed 24 h later. Inflammasome activity (caspase-1 activity, IL-1ß release) and inflammation (Evan's Blue extravasation, bladder weight) were assessed, as was physiological bladder function (urodynamics). RESULTS: Injection of LPS stimulated inflammasome activation (caspase-1 activity) and the release of IL-1ß into the urine which was prevented by glyburide. Likewise, LPS increased inflammation, (bladder weight and the extravasation of Evan's blue dye), and this was reversed by glyburide. Functionally, animals injected with saline alone demonstrated decreased voiding volume as measured by urodynamics. In the presence of LPS, additional urinary dysfunction was evident with decreased voiding pressures and threshold pressures. The decrease in voiding pressure was blocked by glyburide but the decrease in threshold pressure was not, suggesting that LPS has significant effects mediated by inflammasome-dependent and -independent mechanisms. CONCLUSION: Overall, the results demonstrate the potential importance of inflammasomes in bacterial cystitis as well as the ability of the bladder wall injection technique to isolate the in vivo effects of specific inflammasome ligands to the physiological changes associated with cystitis.

Inflammasomes are important mediators of cyclophosphamide-induced bladder inflammation.

Bladder inflammation (cystitis) underlies numerous bladder pathologies and is elicited by a plethora of agents such as urinary tract infections, bladder outlet obstruction, chemotherapies, and catheters. Pattern recognition receptors [Toll-like receptors (TLRs) and Nod-like receptors (NLRs)] that recognize pathogen- and/or damage-associated molecular patterns (PAMPs and/or DAMPs, respectively) are key components of the innate immune system that coordinates the production (TLRs) and maturation (NLRs) of proinflammatory IL-1ß. Despite multiple studies of TLRs in the bladder, none have investigated NLRs beyond one small survey. We now demonstrate that NLRP3 and NLRC4, and their binding partners apoptosis-associated speck-like protein containing a COOH-terminal caspase recruitment domain (ASC) and NLR family apoptosis inhibitory protein (NAIP), are expressed in the bladder and localized predominantly to the urothelia. Activated NLRs form inflammasomes that activate caspase-1. Placement of a NLRP3- or NLRC4-activating PAMP or NLRP3-activating DAMPs into the lumen of the bladder stimulated caspase-1 activity. To investigate inflammasomes in vivo, we induced cystitis with cyclophosphamide (CP, 150 mg/kg ip) in the presence or absence of the inflammasome inhibitor glyburide. Glyburide completely blocked CP-induced activation of caspase-1 and the production of IL-1ß at 4 h. At 24 h, glyburide reduced two markers of inflammation by 30-50% and reversed much of the inflammatory morphology. Furthermore, glyburide reversed changes in bladder physiology (cystometry) induced by CP. In conclusion, NLRs/inflammasomes are present in the bladder urothelia and respond to DAMPs and PAMPs, whereas NLRP3 inhibition blocks bladder dysfunction in the CP model. The coordinated response of NLRs and TLRs in the urothelia represents a first-line innate defense that may provide an important target for pharmacological intervention.

Development of a Peptide-derived orally-active kappa-opioid receptor agonist targeting peripheral pain.

Kappa-opioid agonists are particularly efficacious in the treatment of peripheral pain but suffer from central nervous system (CNS)-mediated effects that limit their development. One promising kappa-agonist is the peptidic compound CR665. Although not orally available, CR665 given i.v. exhibits high peripheral to CNS selectivity and benefits patients with visceral and neuropathic pain. In this study we have generated a series of derivatives of CR665 and screened them for oral activity in the acetic acid-induced rat writhing assay for peripheral pain. Five compounds were further screened for specificity of activation of kappa receptors as well as agonism and antagonism at mu and delta receptors, which can lead to off-target effects. All active derivatives engaged the kappa receptor with EC50s in the low nM range while agonist selectivity for kappa over mu or delta was >11,000-200,000-fold. No antagonist activity was detected. One compound was chosen for further analysis (Compound 9). An oral dose response of 9 in rats yielded an EC50 of 4.7 mg/kg, approaching a druggable level for an oral analgesic. To assess the peripheral selectivity of this compound an i.v. dose response in rats was assessed in the writhing assay and hotplate assay (an assay of CNS-mediated pain). The EC50 in the writhing assay was 0.032 mg/kg while no activity was detectable in the hotplate assay at doses as high as 30 mg/kg, indicating a peripheral selectivity of >900-fold. We propose that compound 9 is a candidate for development as an orally-available peripherally-restricted kappa agonist.

Suramin: a potential therapy for diabetic nephropathy.

OBJECTIVE: To determine whether delayed administration of a single dose of suramin, a drug that has been used extensively in humans to treat trypanosomiasis, attenuates renal injury in a leptin receptor deficient C57BLKS/J db/db type 2 diabetic nephropathy (T2DN) mouse model. RESEARCH DESIGN AND METHODS: Groups of female non-diabetic (control) db/m and diabetic db/db mice of 8 and 16 weeks of age, respectively, were treated with suramin (10 mg/kg) or saline i.v. All animals were euthanized one week later. Measurements in mice 1 week following treatment included the following: body weight; blood glucose; urinary protein excretion; pathological lesions in glomeruli and proximal tubules; changes in protein expression of pro-inflammatory transcription factor nuclear factor κB (NF-κB) and intracellular adhesion molecule-1 (ICAM-1), profibrotic transforming growth factor-ß1 (TGF-ß1), phospho-SMAD-3 and alpha-smooth muscle actin (α-SMA); and immunohistochemical analysis of leukocyte infiltration and collagen 1A2 (COL1A2) deposition. RESULTS: Immunoblot analysis revealed increased NF-κB, ICAM-1, TGF-ß1, phospho-SMAD-3, and α-SMA proteins in both 9 and 17 week db/db mice as compared to db/m control mice. Immunohistochemical analysis revealed moderate leukocyte infiltration and collagen 1A2 (COL1A2) deposition in 9 week db/db mice that was increased in the 17 week db/db mice. Importantly, suramin significantly decreased expression of all these markers in 9 week db/db mice and partially decreased in 17 week db/db mice without altering body weight, blood glucose or urinary protein excretion. There was no difference in creatinine clearance between 9 week db/m and db/db mice ± suramin. Importantly, in the 17 week db/db mice suramin intervention reversed the impaired creatinine clearance and overt histological damage. CONCLUSIONS: Delayed administration of a single dose of suramin in a model of T2DN attenuated inflammation and fibrosis as well as improved renal function, supporting the use of suramin in T2DN.

Diabetes-induced renal injury in rats is attenuated by suramin.

Progression of hyperglycemia-induced renal injury is a contributing factor for diabetic nephropathy (DN)-induced end-stage renal disease (ESRD), and development of novel therapeutic strategies that act early to prevent progression of DN and ESRD are important. We examined the efficacy and mechanism(s) of suramin on hyperglycemia-induced renal injury before development of overt histological damage. Two groups of male Sprague-Dawley rats received streptozotocin (STZ) and one group received saline. Three weeks later, one STZ group received suramin (10 mg/kg). All animals were euthanized 1 week later (4 weeks). Although there was a decrease in creatinine clearance between control and STZ ± suramin rats, there was no difference in creatinine clearance between STZ rats ± suramin intervention. Liquid chromatography-tandem mass spectroscopy-based analysis revealed increases in urinary proteins that are early indicators of DN (e.g., cystatin C, clusterin, cathepsin B, retinol binding protein 4, and peroxiredoxin-1) in the STZ group, which were blocked by suramin. Endothelial intracellular adhesion molecule-1 (ICAM-1) activation, leukocyte infiltration, and inflammation; transforming growth factor-ß1 (TGF-ß1) signaling; TGF-ß1/SMAD-3-activated fibrogenic markers fibronectin-1, α-smooth muscle actin, and collagen 1A2; activation of proinflammatory and profibrotic transcription factors nuclear factor-κB (NF-κB) and signal transducer and activator of transcription factor-3 (STAT-3), respectively, were all increased in STZ rats and suramin blocked these changes. In conclusion, delayed administration of suramin attenuated 1) urinary markers of DN, 2) inflammation by blocking NF-κB activation and ICAM-1-mediated leukocyte infiltration, and 3) fibrosis by blocking STAT-3 and TGF-ß1/SMAD-3 signaling. These results support the potential use of suramin in DN.

Recovery from glycerol-induced acute kidney injury is accelerated by suramin.

Acute kidney injury (AKI) is a common and potentially life-threatening complication after ischemia/reperfusion and exposure to nephrotoxic agents. In this study, we examined the efficacy and mechanism(s) of suramin in promoting recovery from glycerol-induced AKI, a model of rhabdomyolysis-induced AKI. After intramuscular glycerol injection (10 ml of 50% glycerol per kilogram) into male Sprague-Dawley rats, serum creatinine maximally increased at 24 to 72 h and then decreased at 120 h. Creatinine clearance (CrCl) decreased 75% at 24 to 72 h and increased at 120 h. Suramin (1 mg/kg i.v.) administered 24 h after glycerol accelerated recovery of renal function as demonstrated by increased CrCl, decreased renal kidney injury molecule-1, and improved histopathology 72 h after glycerol injection. Suramin treatment decreased interleukin-1ß (IL-1ß) mRNA, transforming growth factor-ß(1) (TGF-ß(1)), phospho-p65 of nuclear factor-κB (NF-κB), and cleaved caspase-3 at 48 h compared with glycerol alone. Suramin treatment also decreased glycerol-induced activation of intracellular adhesion molecule-1 (ICAM-1) and leukocyte infiltration at 72 h. Urinary/renal neutrophil gelatinase-associated lipocalin 2 (NGAL) levels, hemeoxygenase-1 expression, and renal cell proliferation were increased by suramin compared with glycerol alone at 72 h. Mechanistically, suramin decreases early glycerol-induced proinflammatory (IL-1ß and NF-κB) and growth inhibitory (TGF-ß(1)) mediators, resulting in the prevention of late downstream inflammatory effects (ICAM-1 and leukocyte infiltration) and increasing compensatory nephrogenic repair. These results support the hypothesis that delayed administration of suramin is effective in abrogating apoptosis, attenuating inflammation, and enhancing nephrogenic repair after glycerol-induced AKI.

Identification and functional characterization of a stable, centrally active derivative of the neurotensin (8-13) fragment as a potential first-in-class analgesic.

The neurotensin hexapapetide fragment NT(8-13) is a potent analgesic when administered directly to the central nervous system but does not cross the blood-brain barrier. A total of 43 novel derivatives of NT(8-13) were evaluated, with one, ABS212 (1), being most active in four rat models of pain when administered peripherally. Compound 1 binds to human neurotensin receptors 1 and 2 with IC(50) of 10.6 and 54.2 nM, respectively, and tolerance to the compound in a rat pain model did not develop after 12 days of daily administration. When it was administered peripherally, serum levels and neurotensin receptor binding potency of 1 peaked within 5 min and returned to baseline within 90-120 min; however, analgesic activity remained near maximum for >240 min. This could be due to its metabolism into an active fragment; however, all 4- and 5-mer hydrolysis products were inactive. This pharmacokinetic/pharmacodynamic dichotomy is discussed. Compound 1 is a candidate for development as a first-in-class analgesic.