Ketamine cystitis—A long-lasting burning issue in Taiwan

Molecular pathways underlying tissue injuries in the bladder with ketamine cystitis

Ketamine cystitis (KC) is a chronic bladder inflammation leading to urinary urgency, frequency, and pain. The pathogenesis of KC is complicated and involves multiple tissue injuries in the bladder. Recent studies indicated that urothelium disruption, lamina propria fibrosis and inflammation, microvascular injury, neuropathological alterations, and bladder smooth muscle (BSM) abnormalities all contribute to the pathogenesis of KC. Ketamine has been shown to induce these tissue injuries by regulating different signaling pathways. Ketamine can stimulate antiproliferative factor, adenosine triphosphate, and oxidative stress to disrupt urothelium. Lamina propria fibrosis and inflammation are associated with the activation of cyclooxygenase-2, nitric oxide synthase, immunoglobulin E, and transforming growth factor β1. Ketamine contributes to microvascular injury via the N-methyl-D aspartic receptor (NMDAR), and multiple inflammatory and angiogenic factors such as tumor necrosis factor α and vascular endothelial growth factor. For BSM abnormalities, ketamine can depress the protein kinase B, extracellular signal-regulated kinase, Cav1.2, and muscarinic receptor signaling. Elevated purinergic signaling also plays a role in BSM abnormalities. In addition, ketamine affects neuropathological alterations in the bladder by regulating NMDAR- and brain-derived neurotrophic factor-dependent signaling. Inflammatory cells also contribute to neuropathological changes via the secretion of chemical mediators. Clarifying the role and function of these signaling underlying tissue injuries in the bladder with KC can contribute to a better understanding of the pathophysiology of this disease and to the design of effective treatments for KC.

The Immunomodulatory Imbalance in Patients with Ketamine Cystitis

The pathogenesis of ketamine cystitis (KC) has been recently linked with immune response to patients but the same has not yet been established. Hence, this study aims to propose a possible immune mechanism of irreversible bladder damage caused by KC. A total of 53 KC patients and 21 healthy volunteers as controls have been retrospectively assessed. The levels of serum immunoglobulin E (IgE), IL-6, and IFN-γ of KC patients were significantly higher than those of controls, whereas the TGF-β levels of KC patients substantially reduced but the IL-2 and IL-4 levels of KC patients were comparable to those of controls. Moreover, the KC patients had significantly higher counts of T_H1, T_H2, and T_H17 cells than those of controls. The immune response of KC users may begin with the IL-6 production and differentiation of T_H17 and may be followed by alternating between high expressions of T_H1 and T_H2. The IL-6 may further suppress the T_REG cells which can aggravate chronic inflammation in KC patients and the imbalance in T_H17 and T_REG cells may involve the pathogenesis of KC. Further investigation is needed to define the role of IL-6 in T_H1/T_H2/T_H17-regulated signaling pathway in ketamine-induced cystitis.