Selective inhibition of TNFR1 reduces osteoclast numbers and is differentiated from anti-TNF in a LPS-driven model of inflammatory bone loss.

The treatment of autoimmune disorders has been revolutionised by the introduction of biologics such as anti-tumour necrosis factor (anti-TNF). Although in rheumatoid arthritis patients a bone sparing effect of anti-TNF has been shown, the mechanism is not fully understood. Anti-TNF molecules block tumour necrosis factor (TNF) and prevent signalling via both TNF receptor 1 (TNFR1; p55) and TNF receptor 2 (TNFR2; p75). However, signalling via TNFR2 is reported to have protective effects in a number of cell and organ systems. Hence we set out to investigate if pharmacological inhibition of TNFR1 had differential effects compared to pan-TNF inhibition in both an in vitro cell-based model of human osteoclast activity and an in vivo mouse model of lipopolysaccharide (LPS)-induced osteolysis. For the in vitro experiments the anti-human TNFR1 domain antibody (dAb) DMS5541 was used, whereas for the in vivo mouse experiments the anti-mouse TNFR1 dAb DMS5540 was used. We show that selective blocking of TNFR1 signalling reduced osteoclast formation in the presence of TNF. Subcutaneous LPS injection over the calvaria leads to the development of osteolytic lesions within days due to inflammation driven osteoclast formation. In this model, murine TNFR2 genetically fused with mouse IgG1 Fc domain (mTNFR2.Fc), an anti-TNF, did not protect from bone loss in contrast to anti-TNFR1, which significantly reduced lesion development, inflammatory infiltrate, and osteoclast number and size. These results support further exploring the use of TNFR1-selective inhibition in inflammatory bone loss disorders such as osteomyelitis and peri-prosthetic aseptic loosening.

[Calcium-dependent interaction of transducin with calmodulin-sepharose].

It has been shown by affinity chromatography on calmodulin-sepharose that transducin, a G protein of bovine retinal rod outer segments interacts with Ca(2+)-calmodulin. This result assumes that the main part of calmodulin in dark retinal rod outer segments is associated with transducin. It has been suggested that photoactivation of retinal rods induces changes in intracellular calmodulin concentration, which may be one of the steps involved in the light adaptation of photoreceptor.

[Insulin regulation of 2 kinetically different types of calcium current]. / Reguliatsiia insulinom dvukh kineticheski razlichnykh tipov kal'tsievogo toka.

At least two kinetically different kinds of calcium current are shown to exist in the frog atrial cells. The current with faster activation kinetics is usually depressed by insulin. Insulin also increases the amplitude of the slower calcium current. Pretreatment of atrial cells with cycloheximide does not change the effect of insulin on the fast calcium current but dramatically facilitates the insulin-induced activation of the slower calcium current.

Properties and content of cyclic nucleotide phosphodiesterase in photoreceptor outer segments of ground squirrel retina.

Cyclic GMP-specific phosphodiesterase (3',5'-cyclic-nucleotide 5'-nucleotidohydrolase, EC 1.3.4.17) (PDE) is thought to be a key enzyme of the retinal-rod phototransduction cyclic nucleotide pathway. We attempted to investigate the properties and content of PDE in retinal-cone photoreceptors. The fractions obtained from cone-dominant ground squirrel retinas were analyzed for cone visual pigment content and PDE activity. The cone visual pigment content was estimated to be approx. 65 pmol per retina. The distribution of cone visual pigment coincided with that of the PDE activity through several steps of photoreceptor membrane purification by sucrose density gradient centrifugation. The ground squirrel retinal PDE was similar to the retinal-rod PDE by its kinetic properties, thermostability, sensitivity to tryptic activation, Stokes radius and pI values. The cone visual pigment enriched fractions contained the heat-stable trypsin-inactivated PDE inhibitor. Its functional properties seem to be similar to those of the retinal-rod PDE inhibitory subunit. The PDE content in ground squirrel retina was roughly estimated to be about five copies of enzyme per 100 cone visual pigment molecules. The obtained results indicated that the major portion of ground squirrel retinal cyclic GMP-specific PDE is the endogenous cone photoreceptor membrane enzyme and strongly supported the conception about the key role of PDE in cone phototransduction. The existence of essential differences between rod and cone systems rapidly returning cyclic GMP-specific amplification cascade components to the dark (or inactivated) states after photon absorption was suggested. If this suggestion is true, the well-known distinctions between response kinetics and light sensitivity of these two kinds of photoreceptor can be explained.

[Modification by cycloheximide of the effects of insulin on the transport of calcium by sarcolemma of the myocardium]. / Modifikatsiia tsiklogeksimidov éffektov insulina na transport kal'tsiia sarkolemmoi miokarda.

The inhibitory effect of insulin on Ca2+-current was supposed to be due to activation of phosphoproteinphosphotases stimulated by a specific intracellular insulin messenger. The results obtained support the above suggestion. Pretreatment of myocardial preparation with cycloheximide in low concentrations completely blocks the inhibitory insulin effect on Ca2+-current due, probably, to a decrease in peptide formation. Moreover, prolonged effect of the hormone involves a considerable increase of the current as compared to its initial value. Possible mechanisms of modifying effect of cycloheximide on the function of insulin-dependent regulatory system in the myocardium, are discussed.

[Effect of insulin on the calcium current of the frog myocardium]. / Vliianie insulina na kal'tsievyi tok miokarda liagushki.

The experiments on frog atra tuberculae revealed that insulin could induce biphasic changes of calcium currents of different directions. The current is inhibited with hormone due to a decrease both in the conductivity of channel system and reversal potential. In some cases prior to inhibition of calcium current, a short rise of this current occurred (3-6 min) induced by increased reversal potential. Possible mechanisms of insulin electrophysiological effects are discussed.

Role of neurotransmitter release and cyclic AMP-dependent membrane phosphorylation in low voltage myocardial automaticity.

Low voltage myocardial automaticity (LVA) was investigated by pharmacological modulations of the presynaptic and postsynaptic processes. The sensitivity of LVA both to inhibitor and stimulator of neurotransmitter release suggests its involvement in LVA genesis. Moreover, LVA is blocked by the inhibition of the cyclic AMP system, supporting the participation of the c-AMP-dependent membrane phosphorylation in calcium-mediated cardiac electrogenesis.