Vesical-renal reflex: diuresis and natriuresis activated by intravesical capsaicin

Spice Up Your Kidney: A Review on the Effects of Capsaicin in Renal Physiology and Disease

Capsaicin, the organic compound which attributes the spicy flavor and taste of red peppers and chili peppers, has been extensively studied for centuries as a potential natural remedy for the treatment of several illnesses. Indeed, this compound exerts well-known systemic pleiotropic effects and may thus bring important benefits against various pathological conditions like neuropathic pain, rhinitis, itching, or chronic inflammation. Yet, little is known about the possible biological activity of capsaicin at the kidney level, as this aspect has only been addressed by sparse experimental investigations. In this paper, we aimed to review the available evidence focusing specifically on the effects of capsaicin on renal physiology, as well as its potential benefits for the treatment of various kidney disorders. Capsaicin may indeed modulate various aspects of renal function and renal nervous activity. On the other hand, the observed experimental benefits in preventing acute kidney injury, slowing down the progression of diabetic and chronic kidney disease, ameliorating hypertension, and even delaying renal cancer growth may set the stage for future human trials of capsaicin administration as an adjuvant or preventive therapy for different, difficult-to-treat renal diseases.

Bladder cancer and urothelial impairment: the role of TRPV1 as potential drug target

Urothelium, in addition to its primary function of barrier, is now understood to act as a complex system of cell communication that exhibits specialized sensory properties in the regulation of physiological or pathological stimuli. Furthermore, it has been hypothesized that bladder inflammation and neoplastic cell growth, the two most representative pathological conditions of the lower urinary tract, may arise from a primary defective urothelial lining. Transient receptor potential vanilloid channel 1 (TRPV1), a receptor widely distributed in lower urinary tract structures and involved in the physiological micturition reflex, was described to have a pathophysiological role in inflammatory conditions and in the genesis and development of urothelial cancer. In our opinion new compounds, such as curcumin, the major component of turmeric Curcuma longa, reported to potentiate the effects of the chemotherapeutic agents used in the management of recurrent urothelial cancer in vitro and also identified as one of several compounds to own the vanillyl structure required to work like a TRPV1 agonist, could be thought as complementary in the clinical management of both the recurrences and the inflammatory effects caused by the endoscopic resection or intravesical chemotherapy administration or could be combined with adjuvant agents to potentiate their antitumoral effect.

TRP family proteins in the lower urinary tract: translating basic science into new clinical prospective

The lower urinary tract (LUT) is densely innervated by capsaicin-sensitive primary afferent neurons, a sub set of sensory nerves, in a number of species including humans. These fibers exhibit both a sensory (afferent) function, including the regulation of the micturition reflex and the perception of pain, and an 'efferent' function, involved in the detrusor smooth muscle contractility and plasma protein extravasation. The discovery of specific binding sites for capsaicin, the pungent ingredient of red chilli, initiated a rush that ended up with the cloning of the 'vanilloid receptor', which belongs to the TRP (transient receptor potential) family. Here we reviewed the knowledge about the presumable functions of TRP family proteins in the LUT as regulators of bladder reflex activity, pain perception and cell differentiation. This review will focus on experimental evidence and promising clinical applications of targeting these proteins for the treatment of detrusor overactivity and bladder pain syndrome. As TRP receptor ligands may promote cellular death, and inhibit the growth of normal and neoplastic cells, the translation of basic science evidence into new clinical prospective for bladder and prostate cancer will be shown.

Effects of lipids on ENaC activity in cultured mouse cortical collecting duct cells

Direct effects on epithelial Na+ channels (ENaC) activity by lipids, e.g., arachidonic acid (AA), eicosatetraynoic acid (ETYA), linoleic acid (LA), stearic acid (SA), hydroxyeicosatetraenoic acid (HETE), 11,12-epoxyeicosatrienoic acid (EET), (PGF2), and (PGE2), in cultured mouse cortical collecting duct (M1) cells were clarified by using single-channel recordings in this study. In a cell-attached recording, a bath application of 10 microM AA significantly reduced the ENaC open probability (NPo), whereas 10 microM ETYA or 5 microM LA only induced a slight inhibition. The inside-out recording as a standard protocol was thereafter performed to examine effects of these lipids on ENaC activity. Within 10 min after the formation of the inside-out configuration, the NPo of ENaC in cultured mouse cortical collecting duct (M1) cells remained relatively constant. Application of ETYA or LA or SA exhibited a similar inhibition on the channel NPo when applied to the extracellular side, suggesting that fatty acids could exert a nonspecific inhibition on ENaC activity. 11,12-EET, a metabolite of AA via the cytochrome P450 epoxygenase pathway, significantly inhibited the ENaC NPo, whereas 20-HETE, a metabolite of AA via the hydroxylase pathway, only caused a small inhibition of the ENaC NPo, to a similar degree as that seen with ETYA and LA. However, both PGE2 and PGF2alpha significantly enhanced the ENaC NPo. These results suggest that fatty acids exert a nonspecific effect on ENaC activity due to the interaction between the channel proximity and the lipid. The opposite effects of 11,12-EET and prostaglandin (PG) implicate different mechanisms in regulation of ENaC activity by activation of epoxygenase and cyclooxygenase.

On the origin of bladder sensing: Tr(i)ps in urology

The mammalian TRP family consists of 28 channels that can be subdivided into 6 different classes: TRPV (vanilloid), TRPC (canonical), TRPM (Melastatin), TRPP (Polycystin), TRPML (Mucolipin), and TRPA (Ankyrin). TRP channels are activated by a diversity of physical (voltage, heat, cold, mechanical stress) or chemical (pH, osmolality) stimuli and by binding of specific ligands, enabling them to act as multifunctional sensors at the cellular level. Currently, a lot of scientific research is devoted to these channels and their role in sensing mechanisms throughout the body. In urology, there's a growing conviction that disturbances in afferent (sensory) mechanisms are highly important in the pathogenesis of functional problems. Therefore, the TRP family forms an interesting new target to focus on. In this review we attempt to summarize the existing knowledge about TRP channels in the urogenital tract. So far, TRPV1, TRPV2, TRPV4, TRPM8, and TRPA1 have been described in different parts of the urogenital tract. Although only TRPV1 (the vanilloid receptor) has been extensively studied so far, more evidence is slowly accumulating about the role of other TRP channels in the (patho)physiology of the urogenital tract.

Intra-ureteric capsaicin in loin pain haematuria syndrome: efficacy and complications

OBJECTIVE

To evaluate the safety and efficacy of intra-ureteric capsaicin for loin pain haematuria syndrome (LPHS).

PATIENTS AND METHODS

In an open prospective pilot study, four middle-aged patients (three women and one man) with LPHS resistant to therapies such as splanchnic nerve block, psychological treatment or renal autotransplantation (one) were assessed. An intra-ureteric infusion of capsaicin (30 mg/100 mL of 30% alcohol in saline) for 30 min with bladder irrigation was administered under general anaesthesia, with a subsequent intravenous patient-controlled narcotic analgesic pump for pain control. Double-concentration capsaicin was used for second infusions, if necessary when the response to the earlier infusion was inadequate or incomplete.

RESULTS

The first patient had experienced reduced pain levels for the first 3 months only, with no benefit from the subsequent treatments with higher doses of capsaicin (60 mg). The second patient with recurrent pain in an autotransplanted kidney had no benefit from either a 30 or 60 mg capsaicin infusion a month apart, but developed a fibrotic stricture at the transplant pelvi-ureteric junction, requiring pyelocystoplasty. The third patient with concurrent depression had no benefit from a 30-mg infusion of capsaicin. The fourth patient experienced no pain relief from a 30 mg infusion of capsaicin but developed proteinuria secondary to mesangial proliferative glomerulonephritis, ureteric inflammation needing stenting within 7 days of treatment and subsequently nephrectomy for a nonfunctioning kidney at 3 months.

CONCLUSION

Intra-ureteric capsaicin was neither effective nor safe in LPHS; the contribution of the alcohol diluent cannot be excluded.