Certain human malignancies including prostate cancer overexpress sigma receptor, a membrane bound protein that binds haloperidol and various other neuroleptics with high affinity. An anisamide derivatized ligand possesses high affinity for sigma receptors and we hypothesized that its incorporation into the liposomes encapsulating doxorubicin (DOX) can specifically target and deliver the drug to prostate cancer cells that overexpress sigma receptors. A polyethylene glycol phospholipid was derivatized with an anisamide ligand, which was then incorporated into the DOXloaded liposome. The resulting anisamide-conjugated liposomal DOX showed significantly higher toxicity to DU-145 cells than non-targeted liposomal DOX, the IC50 being 1.8 M and 14 M respectively. The cytotoxicity of the targeted liposomal DOX, however, was significantly blocked by haloperidol, suggesting that the enhanced cytotoxicity was specifically mediated by the sigma receptors. Fluorescence imaging studies after intravenous (i.v.) administration showed that incorporation of anisamide into liposomes significantly improved their accumulation into the tumor. A weekly injection of the targeted liposomal DOX for 4 weeks at a dose of 7.5 mg/kg led to a significant growth inhibition of established DU-145 tumor in nude mice with minimal toxicity. Free DOX was effective, but associated with significant toxicities. The present study is the first to demonstrate the use of small molecular weight ligand for mediating efficient targeting of liposomal drugs to sigma receptor expressing prostate cancer cells both in vitro and in vivo.

The presence of elevated levels in urine of inflammatory biomarkers involved in inflammation and tissue repair suggests a role for inflammation in OAB, and may help in diagnosis and treatment of this disease.

Selective targeting of ligand-targeted liposomes containing anticancer drugs or therapeutic genes to cell surface receptors expressed on cancer cells is a recognized strategy for improving the therapeutic effectiveness of conventional chemotherapeutics or gene therapeutics. Some recent advances in the field of ligand-targeted liposomes for the treatment of cancer are summarized including: selection criteria for the receptors to be targeted, choice of targeting ligands and choice of encapsulated therapeutics. Targeting of liposomes to solid tumors, versus angiogenic endothelial cells versus vascular targets is discussed. Ligand-targeted liposomes have shown considerable promise in preclinical xenograft models and are poised for clinical development.

The functions of the lower urinary tract, to store and periodically release urine, are dependent on the activity of smooth and striated muscles in the bladder, urethra, and external urethral sphincter. During urine storage, the outlet is closed, and the bladder smooth muscle is quiescent. When bladder volume reaches the micturition threshold, activation of a micturition center in the dorsolateral pons (the pontine micturition center) induces a bladder contraction and a reciprocal relaxation of the urethra, leading to bladder emptying. During voiding, sacral parasympathetic (pelvic) nerves provide an excitatory input (cholinergic and purinergic) to the bladder and inhibitory input (nitrergic) to the urethra. These peripheral systems are integrated by excitatory and inhibitory regulation at the levels of the spinal cord and the brain. Injury or diseases of the nervous system, as well as drugs and disorders of the peripheral organs, can produce lower urinary tract dysfunction. In the overactive bladder (OAB) condition, therapeutic targets for facilitation of urine storage can be found at the levels of the urothelium, detrusor muscles, autonomic and afferent pathways, spinal cord, and brain. There is increasing evidence showing that the urothelium has specialized sensory and signaling properties including: (1) expression of nicotinic, muscarinic, tachykinin, adrenergic, bradykinin, and transient receptor potential (TRP) receptors, (2) close physical association with afferent nerves, and (3) ability to release chemical molecules such as adenosine triphosphate (ATP), acetylcholine, and nitric oxide. Increased expression and/or sensitivity of these urothelial-sensory molecules that lead to afferent sensitization have been documented as possible pathogenesis of OAB. Targeting afferent pathways and/or bladder smooth muscles by modulating activity of ligand receptors (e.g., neurokinin, ATP, or beta3-adrenergic receptors) and ion channels (e.g., TRPV1 or K) could be effective to suppress OAB. In the stress urinary incontinence condition, pharmacotherapies targeting the neurally mediated urethral continence reflex during stress conditions such as sneezing or coughing could be effective for increasing the outlet resistance. Therapeutic targets include adrenergic and serotonergic receptors in the spinal cord as well as adrenergic receptors at the urethral sphincter, which can enhance urethral reflex activity during stress conditions and increase baseline urethral pressure, respectively.

Key pointsr ATP is released through pannexin channels into the lumen of the rat urinary bladder in response to distension or stimulation with bacterial endotoxins.r Luminal ATP plays a physiological role in the control of micturition because intravesical perfusion of apyrase or the ecto-ATPase inhibitor ARL67156 altered reflex bladder activity in the anaesthetized rat.r The release of ATP from the apical and basolateral surfaces of the urothelium appears to be mediated by separate mechanisms because intravesical administration of the pannexin channel antagonist Brilliant Blue FCF increased bladder capacity, whereas I.V. administration did not.r Intravesical instillation of small interfering RNA-containing liposomes decreased pannexin 1 expression in the rat urothelium in vivo and increased bladder capacity.r These data indicate a role for pannexin-mediated luminal ATP release in both the physiological and pathophysiological control of micturition and suggest that urothelial pannexin may be a viable target for the treatment of overactive bladder disorders.Abstract ATP is released from the bladder epithelium, also termed the urothelium, in response to mechanical or chemical stimuli. Although numerous studies have described the contribution of this release to the development of various bladder disorders, little information exists regarding the mechanisms of release. In the present study, we examined the role of pannexin channels in mechanically-induced ATP release from the urothelium. PCR confirmed the presence of pannexin 1 and 2 mRNA in rat urothelial tissue, whereas immunofluorescence experiments localized pannexin 1 to all three layers of the urothelium. During continuous bladder cystometry in anaesthetized rats, inhibition of pannexin 1 channels using carbenoxolone (CBX) or Brilliant Blue FCF (BB-FCF) (1-100 μM, intravesically), or by using intravesical small interfering RNA, increased the interval between voiding contractions. Intravenous administration of BB-FCF (1-100 μg kg −1 ) did not alter bladder activity. CBX or BB-FCF (100 μM intravesically) also decreased basal ATP concentrations in the perfusate from non-distended bladders and inhibited increases in ATP concentrations in response to bladder distension (15 and 30 cmH 2 O pressure). Intravesical perfusion of the ATP diphosphohydrolase apyrase (2 U ml −1 ), or the ATPase inhibitor ARL67156 (10 μM) increased or decreased reflex bladder activity, respectively. Intravesical instillation of bacterial lipopolysaccharides (LPS) (Escherichia coli 055:B5, 100 μg ml −1 ) increased ATP concentrations in the bladder perfusate, and also increased voiding frequency; these effects were suppressed by BB-FCF. These data indicate that pannexin channels contribute to distension-or LPS-evoked ATP release into the lumen of the bladder and that luminal release can modulate voiding function.