Expression and characteristics of ion channels in osteoblasts : putative roles for TRP and K+ channels

Bone turnover is regulated by a cocktail of hormones and signalling factors controlling key cell processes such as proliferation, differentiation, mineralisation and apoptosis. Disruption to the overall mineralisation-resorption balance leads to bone disorders, such as osteoporosis - a 'silent' disease affecting around 7 million people in England and Wales. Ion channels that are presumed targets for bone signalling factors include voltage-gated K channels, ATP-dependent K channels and transient receptor potential TRP channels, and several of these channel-types reportedly have roles in cell proliferation, apoptosis, and differentiation in various tissues. This Thesis shows that human osteoblasts express a number of channels in these families, including maxi-K, ATP-dependent K channels, TRPV1 and TRPM7. The maxi-K channel, displaying characteristic electrophysiological hallmarks, is abundant in patch-clamp recordings of primary human osteoblasts implying a functional role, and the Katp agonist pinacidil is shown to promote osteoblast proliferation. Electrophysiological evidence for the TRPVI channel is not found, although the mRNA signal for a TRPVI splice variant TRPVlb may provide an answer, as it renders the channel less sensitive to capsaicin and protons. However, Ca imaging indicates that osteoblastic TRPV1 channels allow Ca2 influx, and are sensitive to 1 µM capsaicin and protons. In functional studies the TRPVI ligands capsaicin and capsazepine do not influence mineralisation, but interestingly the TRPVI agonists capsaicin, resiniferatoxin and anandamide appear to prevent differentiation of osteoblastic pre-cursor cells to adipocytes, and instead encourage maturation along the osteoblast pathway, whilst TRPV1 antagonists do not affect adipocyte differentiation. In conclusion, a number of K channels and the TRPV1 channel are expressed in osteoblasts and may have important putative roles in osteoblast cell function. Further steps are required to confirm this before the channels can be considered targets for drug development to treat bone disorders.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Expression and characteristics of ion channels in osteoblasts : putative roles for TRP and K+ channels.

Bone turnover is regulated by a cocktail of hormones and signalling factors controlling key cell processes such as proliferation, differentiation, mineralisation and apoptosis. Disruption to the overall mineralisation-resorption balance leads to bone disorders, such as osteoporosis - a 'silent' disease affecting around 7 million people in England and Wales. Ion channels that are presumed targets for bone signalling factors include voltage-gated K channels, ATP-dependent K channels and transient receptor potential TRP channels, and several of these channel-types reportedly have roles in cell proliferation, apoptosis, and differentiation in various tissues. This Thesis shows that human osteoblasts express a number of channels in these families, including maxi-K, ATP-dependent K channels, TRPV1 and TRPM7. The maxi-K channel, displaying characteristic electrophysiological hallmarks, is abundant in patch-clamp recordings of primary human osteoblasts implying a functional role, and the Katp agonist pinacidil is shown to promote osteoblast proliferation. Electrophysiological evidence for the TRPVI channel is not found, although the mRNA signal for a TRPVI splice variant TRPVlb may provide an answer, as it renders the channel less sensitive to capsaicin and protons. However, Ca imaging indicates that osteoblastic TRPV1 channels allow Ca2 influx, and are sensitive to 1 uM capsaicin and protons. In functional studies the TRPVI ligands capsaicin and capsazepine do not influence mineralisation, but interestingly the TRPVI agonists capsaicin, resiniferatoxin and anandamide appear to prevent differentiation of osteoblastic pre-cursor cells to adipocytes, and instead encourage maturation along the osteoblast pathway, whilst TRPV1 antagonists do not affect adipocyte differentiation. In conclusion, a number of K channels and the TRPV1 channel are expressed in osteoblasts and may have important putative roles in osteoblast cell function. Further steps are required to confirm this before the channels can be considered targets for drug development to treat bone disorders

RNA Silencing in the Management of Dyslipidemias

PURPOSE OF REVIEW: Remarkable reductions in cardiovascular morbidity and mortality have been achieved in recent decades through the widespread use of ‘small-molecule’ hypolipidaemic drugs such as statins and ezetimibe. An alternative approach is to perturb the production of proteins through ribonucleic acid (RNA) silencing, leading to long-lasting knock-down of specific biological molecules. This review describes the scientific basis of RNA silencing, and critically evaluates the evidence relating to inclisiran, a small interfering RNA against proprotein convertase subtilisin kexin 9 (PCSK9). RECENT FINDINGS: Pooled analysis of three recent ORION trials has demonstrated that twice-yearly administration of inclisiran reduces LDL-C by 50% in a range of patient groups, with only mild adverse effects. SUMMARY: Inclisiran provides safe, effective and long-lasting reductions in PCSK9 and LDL-C. The results of the phase-3 ORION-4 outcomes study are eagerly awaited. Further promising RNA silencing technologies have the potential to improve the management of dyslipidaemia

Phytochemicals as inhibitors of tumor necrosis factor alpha and neuroinflammatory responses in neurodegenerative diseases

Inflammatory processes and proinflammatory cytokines have a key role in the cellular processes of neurodegenerative diseases and are linked to the pathogenesis of functional and mental health disorders. Tumor necrosis factor alpha has been reported to play a major role in the central nervous system in Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis and many other neurodegenerative diseases. Therefore, a potent proinflammatory/proapoptotic tumor necrosis factor alpha could be a strong candidate for targeted therapy. Plant derivatives have now become promising candidates as therapeutic agents because of their antioxidant and chemical characteristics, and anti-inflammatory features. Recently, phytochemicals including flavonoids, terpenoids, alkaloids, and lignans have generated interest as tumor necrosis factor alpha inhibitor candidates for a number of diseases involving inflammation within the nervous system. In this review, we discuss how phytochemicals as tumor necrosis factor alpha inhibitors are a therapeutic strategy targeting neurodegeneration

Update on Statin Treatment in Patients with Neuropsychiatric Disorders

Statins are widely accepted as first-choice agents for the prevention of lipid-related cardiovascular diseases. These drugs have both anti-inflammatory and anti-oxidant properties, which may also make them effective as potential treatment marked by perturbations in these pathways, such as some neuropsychiatric disorders. In this narrative review, we have investigated the effects of statin therapy in individuals suffering from major depressive disorder (MDD), schizophrenia, anxiety, obsessive-compulsive disorder (OCD), bipolar disorder (BD), delirium, and autism spectrum disorders using a broad online search of electronic databases. We also explored the adverse effects of these drugs to obtain insights into the benefits and risks associated with their use in the treatment of these disorders. Lipophilic statins (including simvastatin) because of better brain penetrance may have greater protective effects against MDD and schizophrenia. The significant positive effects of statins in the treatment of anxiety disorders without any serious adverse side effects were shown in numerous studies. In OCD, BD, and delirium, limitations, and contradictions in the available data make it difficult to draw conclusions on any positive effect of statins. The positive effects of simvastatin in autism disorders have been evaluated in only a small number of clinical trials. Although some studies showed positive effect of statins in some neuropsychiatric disorders, further prospective studies are needed to confirm this and define the most effective doses and treatment durations

A large-conductance (BK) potassium channel subtype affects both growth and mineralization of human osteoblasts

The pharmacology of the large-conductance K+ (BK) channel in human osteoblasts is not well defined, and its role in bone is speculative. Here we assess BK channel properties in MG63 cells and primary human osteoblasts and determine whether pharmacological modulation affects cell function. We used RT-PCR and patch-clamp methods to determine the expression of BK channel subunits and cell number assays in the absence and presence of BK channel modulators. RT-PCR showed the presence of KCNMA1, KCNMB1, KCNMB2, KCNMB3, and KCNMB4 subunits. The BK channel was voltage dependent, with a mean unitary conductance of 228.8 pS (n = 10) in cell-attached patches (140 mM K+/140 mM K+) and a conductance of 142.5 pS (n = 16) in excised outside-out and 155 pS (n = 6) in inside-out patches in 3 mM K+/140 mM K+. The selectivity ratio (ratio of K+ to Na+ permeability) was 15:1. The channel was blocked by tetraethylammonium (TEA, 0.3 mM), iberiotoxin (5–60 nM), tetrandrine (5–30 μM), and paxilline (10 μM) and activated by isopimaric acid (20 μM). BK channel modulators affected MG63 cell numbers: TEA and tetrandrine significantly increased cell numbers at low concentrations (3 mM and 3 μM, respectively) and reduced cell numbers at higher concentrations (>10 mM and >10 μM, respectively). Neither iberiotoxin (20–300 nM) nor slotoxin (300 nM) affected cell numbers. The increase in cell numbers by TEA was blocked by isopimaric acid. TEA (0.1–3.0 mM) significantly increased mineralization in primary osteoblasts. In conclusion, the BK channel has a distinctive pharmacology and is thus a target for therapeutic strategies aimed at modulating osteoblast proliferation and function