We have derived a cardiac muscle cell line, designated HL-1, from the AT-1 mouse atrial cardiomyocyte tumor lineage. HL-1 cells can be serially passaged, yet they maintain the ability to contract and retain differentiated cardiac morphological, biochemical, and electrophysiological properties. Ultrastructural characteristics typical of embryonic atrial cardiac muscle cells were found consistently in the cultured HL-1 cells. Reverse transcriptase–PCR-based analyses confirmed a pattern of gene expression similar to that of adult atrial myocytes, including expression of α-cardiac myosin heavy chain, α-cardiac actin, and connexin43. They also express the gene for atrial natriuretic factor. Immunohistochemical staining of the HL-1 cells indicated that the distribution of the cardiac-specific markers desmin, sarcomeric myosin, and atrial natriuretic factor was similar to that of cultured atrial cardiomyocytes. A delayed rectifier potassium current ( I _Kr ) was the most prominent outward current in HL-1 cells. The activating currents displayed inward rectification and deactivating current tails were voltage-dependent, saturated at ≫+20 mV, and were highly sensitive to dofetilide (IC ₅₀ of 46.9 nM). Specific binding of [ ³ H]dofetilide was saturable and fit a one-site binding isotherm with a K _d of 140 +/− 60 nM and a B _max of 118 fmol per 10 ⁵ cells. HL-1 cells represent a cardiac myocyte cell line that can be repeatedly passaged and yet maintain a cardiac-specific phenotype.

We have studied the effects of bupivacaine on human and bovine articular chondrocytes in vitro. Time-lapse confocal microscopy of human articular chondrocytes showed > 95% cellular death after exposure to 0.5% bupivacaine for 30 minutes. Human and bovine chondrocytes exposed to 0.25% bupivacaine had a time-dependent reduction in viability, with longer exposure times resulting in higher cytotoxicity. Cellular death continued even after removal of 0.25% bupivacaine. After exposure to 0.25% bupivacaine for 15 minutes, flow cytometry showed bovine chondrocyte viability to be 41% of saline control after seven days. After exposure to 0.125% bupivacaine for up to 60 minutes, the viability of both bovine and human chondrocytes was similar to that of control groups. These data show that prolonged exposure 0.5% and 0.25% bupivacaine solutions are potentially chondrotoxic.

Amyloid beta (Abeta) 1–42 oligomers accumulate in brains of patients with Mild Cognitive Impairment (MCI) and disrupt synaptic plasticity processes that underlie memory formation. Synaptic binding of Abeta oligomers to several putative receptor proteins is reported to inhibit long-term potentiation, affect membrane trafficking and induce reversible spine loss in neurons, leading to impaired cognitive performance and ultimately to anterograde amnesia in the early stages of Alzheimer's disease (AD). We have identified a receptor not previously associated with AD that mediates the binding of Abeta oligomers to neurons, and describe novel therapeutic antagonists of this receptor capable of blocking Abeta toxic effects on synapses in vitro and cognitive deficits in vivo. Knockdown of sigma-2/PGRMC1 (progesterone receptor membrane component 1) protein expression in vitro using siRNA results in a highly correlated reduction in binding of exogenous Abeta oligomers to neurons of more than 90%. Expression of sigma-2/PGRMC1 is upregulated in vitro by treatment with Abeta oligomers, and is dysregulated in Alzheimer's disease patients' brain compared to age-matched, normal individuals. Specific, high affinity small molecule receptor antagonists and antibodies raised against specific regions on this receptor can displace synthetic Abeta oligomer binding to synaptic puncta in vitro and displace endogenous human AD patient oligomers from brain tissue sections in a dose-dependent manner. These receptor antagonists prevent and reverse the effects of Abeta oligomers on membrane trafficking and synapse loss in vitro and cognitive deficits in AD mouse models. These findings suggest sigma-2/PGRMC1 receptors mediate saturable oligomer binding to synaptic puncta on neurons and that brain penetrant, small molecules can displace endogenous and synthetic oligomers and improve cognitive deficits in AD models. We propose that sigma-2/PGRMC1 is a key mediator of the pathological effects of Abeta oligomers in AD and is a tractable target for small molecule disease-modifying therapeutics.

Background Chronic pressure and volume overload (PO and VO) result in morphologically and functionally distinct forms of myocardial hypertrophy. We tested the hypothesis that PO- and VO-induced left ventricular (LV) hypertrophies are associated with distinct molecular phenotypes and patterns of peptide growth factor induction. Methods and Results mRNA levels were quantified in LV myocardium from rats with LV hypertrophy due to PO or VO caused by suprarenal aortic constriction or an abdominal aortocaval fistula, respectively, for 1 week. Although PO and VO caused comparable increases in LV weight and prepro–atrial natriuretic factor mRNA, PO but not VO increased mRNA levels for the fetal genes β-myosin heavy chain and skeletal α-actin and reduced the mRNA level of sarcoplasmic reticulum Ca ²⁺ ATPase. In a myocyte-enriched myocardial fraction, transforming growth factor-β ₃ and insulin-like growth factor-1 mRNA levels were increased with PO but not VO; acidic fibroblast growth factor mRNA was unchanged with PO but decreased with VO. In a nonmyocyte-enriched myocardial fraction, transforming growth factor-β ₃ and insulin-like growth factor-1 mRNA levels were decreased with VO but unchanged with PO. Conclusions PO- and VO-induced LV hypertrophies are associated with distinct molecular phenotypes and patterns of peptide growth factor induction. Stimulus-specific heterogeneity in the signaling events and peptide growth factors coupled to gene expression could play a role in determining the type of hypertrophy that is caused by various forms of hemodynamic overload.