Caffeine interaction with the Ca-release channels of heavy sarcoplasmic reticulum. Evidence that 170 kD Ca-binding protein is a caffeine receptor of the Ca-channels

Differential effects of caffeine on hair shaft elongation, matrix and outer root sheath keratinocyte proliferation, and transforming growth factor-β2/insulin-like growth factor-1-mediated regulation of the hair cycle in male and female human hair follicles in vitro

BACKGROUND

Caffeine reportedly counteracts the suppression of hair shaft production by testosterone in organ-cultured male human hair follicles (HFs).

OBJECTIVES

We aimed to investigate the impact of caffeine (i) on additional key hair growth parameters, (ii) on major hair growth regulatory factors and (iii) on male vs. female HFs in the presence of testosterone.

METHODS

Microdissected male and female human scalp HFs were treated in serum-free organ culture for 120 h with testosterone alone (0·5 μg mL(-1)) or in combination with caffeine (0·005-0·0005%). The following effects on hair shaft elongation were evaluated by quantitative (immuno)histomorphometry: HF cycling (anagen-catagen transition); hair matrix keratinocyte proliferation; expression of a key catagen inducer, transforming growth factor (TGF)-β2; and expression of the anagen-prolonging insulin-like growth factor (IGF)-1. Caffeine effects were further investigated in human outer root sheath keratinocytes (ORSKs).

RESULTS

Caffeine enhanced hair shaft elongation, prolonged anagen duration and stimulated hair matrix keratinocyte proliferation. Female HFs showed higher sensitivity to caffeine than male HFs. Caffeine counteracted testosterone-enhanced TGF-β2 protein expression in male HFs. In female HFs, testosterone failed to induce TGF-β2 expression, while caffeine reduced it. In male and female HFs, caffeine enhanced IGF-1 protein expression. In ORSKs, caffeine stimulated cell proliferation, inhibited apoptosis/necrosis, and upregulated IGF-1 gene expression and protein secretion, while TGF-β2 protein secretion was downregulated.

CONCLUSIONS

This study reveals new growth-promoting effects of caffeine on human hair follicles in subjects of both sexes at different levels (molecular, cellular and organ).

Histidine-containing dipeptides as endogenous regulators of the activity of sarcoplasmic reticulum Ca-release channels

It is shown that histidine-containing dipeptide carnosine (beta-alanyl-L-histidine), which is present in skeletal muscles in millimolar concentrations, decreases the rate of Ca2+ accumulation by the heavy fraction of sarcoplasmic reticulum from rabbit skeletal muscles. This effect results from the ability of carnosine to induce a rapid Ca2+ release from the heavy sarcoplasmic reticulum vesicles via activation of the ruthenium red-sensitive Ca-channels. The effect of carnosine is dose-dependent that indicates the presence of saturable site(s) for carnosine in the molecules of Ca-channels. The C0.5 value carnosine (the concentration that induces the half-maximal Ca2+ release) is 8.7 mM. The 1 N-methylated derivative of carnosine, i.e., anserine, also induces a rapid Ca2+ release with the half-maximal effect at 2.7 mM. Conversely, neither histidine nor beta-alanine (both separately and in the mixture) cause Ca2+ release. In addition, carnosine increases the sensitivity of Ca-channels to their well-known activators (caffeine, AMP, and Ca2+) and decreases inhibitory effect of low concentrations of Mg2+. It is concluded that carnosine as a component of skeletal muscles can be an endogenous regulator of the sarcoplasmic reticulum Ca-channel activity.

The identification of the phosphorylated 150/160-kDa proteins of sarcoplasmic reticulum, their kinase and their association with the ryanodine receptor

In the present work we studied the relationship between the phosphorylated 150- and 160-kDa proteins and other SR proteins in the 150,000-170,000 range of molecular masses. on SDS-PAGE, the identification of their kinase, as well as the purification and structural interactions between these proteins and the rynodine receptor (RyR). The phosphorylated 150-kDa protein was identified as sarcalumenin based on: (a) its cross-reactivity with three different monoclonal antibodies specific for sarcalumenin. (b) its mobility in SDS-PAGE which was modified upon digestion with endoglycosidase H, (c) its elution from lentil-lectin column by alpha-methyl mannoside, (d) its resistance to trypsin, (e) its ability to bind Ca2+ and to stain blue with Stains-All. The phosphorylated 160-kDa protein was identified as the histidine-rich Ca2+ binding protein (HCP) based on: (a) its Ca(2+)-binding property and staining blue with Stains-All, (b) phosphorylation with the catalytic subunit of cAMP-dependent kinase. (c) its increased mobility in SDS-PAGE in the presence of Ca2+ (d) its heat stability and (e) its partial amino acid sequence. The endogenous kinase was identified as casein kinase II (CK II) based on the inhibition of the endogenous phosphorylation 160/150-kDa proteins by heparin, 5.6-dichlorobenzimidazole riboside, polyaspartyl peptide and hemin, and its ability to use [gamma-32P]GTP as the phosphate donor. The association of CK II with SR membranes, was demonstrated using specific polyclonal anti-CK II antibodies. The luminal location of CK II is suggested because CK II was extracted from the SR by l M NaCl only after their treatment with hypotonic medium, and CK II activity was inhibited with the charged inhibitors heparin and polyaspartyl peptide only after their incubation with the SR in the presence of NP-40. The 160- and 150-kDa proteins were purified on spermine-agarose column, and were phosphorylated by CK II. Like the endogenous phosphorylation of the 150/160-kDa proteins in SR. the phosphorylation of the purified proteins by CK II was inhibited by La3+ (Cl50 = 4 microM) and hemin. The results suggest the phosphorylation of the luminally located sarcalumenin and HCP with CK II.

Thermal uncoupling of the Ca(2+)-transporting ATPase in sarcoplasmic reticulum. Changes in surface properties of light vesicles

It is known that the light fraction of rabbit skeletal muscle sarcoplasmic reticulum vesicles can release Ca2+ from the intravesicular space, although the Ca(2+)-conductive channels are present only in the heavy fraction of sarcoplasmic reticulum vesicles. To study the possible pathways of the Ca2+ leakage from light vesicles we have used a short-term treatment for 4.5 min at 45 degrees C which quickly decreases the efficiency of Ca(2+)-transporting ATPase operation without any visible effects on the hydrolytic activity of the Ca(2+)-ATPase in the membranes. The treatment of the vesicles decreased the negative membrane surface potential created by the Ca(2+)-ATPase. Comparative titration of control and heat-treated preparations of light sarcoplasmic reticulum vesicles by K+, Na+, Mg2+, and Ca2+ revealed clear differences in their surface properties. The short-term heating resulted in release of Ca2+ from the vesicles previously loaded with 45Ca2+, which indicates an increase in passive membrane permeability to Ca2+. Study of Ca(2+)-ATPase protein arrangement in the membrane indicated that the heat treatment induced protein oligomerization and some of the Ca(2+)-ATPase molecules acquired intermolecular and intramolecular covalent bonds. From these data, we have concluded that the changes in the surface and structure properties of the vesicle membranes after the short-term heat treatment were the result of clustering of the Ca(2+)-ATPase molecules. This protein rearrangement may create channels for calcium leakage from light sarcoplasmic reticulum vesicles.

Caffeine and the central nervous system: mechanisms of action, biochemical, metabolic and psychostimulant effects

Caffeine is the most widely consumed central-nervous-system stimulant. Three main mechanisms of action of caffeine on the central nervous system have been described. Mobilization of intracellular calcium and inhibition of specific phosphodiesterases only occur at high non-physiological concentrations of caffeine. The only likely mechanism of action of the methylxanthine is the antagonism at the level of adenosine receptors. Caffeine increases energy metabolism throughout the brain but decreases at the same time cerebral blood flow, inducing a relative brain hypoperfusion. Caffeine activates noradrenaline neurons and seems to affect the local release of dopamine. Many of the alerting effects of caffeine may be related to the action of the methylxanthine on serotonin neurons. The methylxanthine induces dose-response increases in locomotor activity in animals. Its psychostimulant action on man is, however, often subtle and not very easy to detect. The effects of caffeine on learning, memory, performance and coordination are rather related to the methylxanthine action on arousal, vigilance and fatigue. Caffeine exerts obvious effects on anxiety and sleep which vary according to individual sensitivity to the methylxanthine. However, children in general do not appear more sensitive to methylxanthine effects than adults. The central nervous system does not seem to develop a great tolerance to the effects of caffeine although dependence and withdrawal symptoms are reported.

Characterization of Ca(2+)-dependent endogenous phosphorylation of 160,000- and 150,000-Dalton proteins of sarcoplasmic reticulum

The 160 and 150 kDa proteins of sarcoplasmic reticulum (SR) are phosphorylated endogenously. The phosphorylation of both proteins has a marked requirement for Ca2+. Half-maximal and maximal phosphorylation was obtained at about 1 nM- and 1 microM-Ca2+ respectively, and a Hill coefficient of about 0.5 was calculated. The phosphorylation is also dependent on NaF as an inhibitor of the SR phosphoprotein phosphatase. The phosphorylation of these proteins is very rapid, and maximal phosphorylation is achieved in less than 15 s. The phosphorylation of the 160 kDa and 150 kDa polypeptides is completely inhibited by 5 mM-MgCl2 and by 75 microM-LaCl3, by very low concentrations of different detergents, and by preincubation of the SR for 2 min at 60 degrees C. The inhibition by Mg2+ is due to stimulation of ATP hydrolysis, thereby decreasing ATP concentration. Different phosphorylated peptides were obtained by digestion with protease V8 of the 160 kDa and 150 kDa protein bands, suggesting that the 160 kDa and 150 kDa proteins are distinct. The two phosphorylated proteins are present in different fractions and preparations of SR, with or without [3H]PN200-110 binding capacity. These and other results suggest that the phosphorylated SR proteins are distinct from the alpha 1 and alpha 2 subunits of the voltage-gated Ca2+ channel of the T-system membranes. Different inhibitors and activators of protein kinase C and calmodulin-dependent protein kinase have no effect on the endogenous phosphorylation of both polypeptides, suggesting that the phosphorylation is regulated solely by Ca2+. A possible regulatory function for this phosphorylation system is described in the accompanying paper [Gechtman. Orr & Shoshan-Barmatz (1991) Biochem. J. 276.97-102].

Involvement of protein phosphorylation in activation of Ca2+ efflux from sarcoplasmic reticulum

Preincubation of sarcoplasmic reticulum (SR) membranes with a combination of ATP and NaF resulted in inhibition of Ca2+ accumulation and stimulation of Ca(2+)-ATPase and Ca2+ efflux. Under the same conditions, the activity of the SR phosphoprotein phosphatase was inhibited and the phosphorylation of two polypeptides with apparent molecular masses of 160 and 150 kDa was obtained. The effect of ATP is specific, since the ATP analogue adenosine 5'-[beta gamma-imido]triphosphate did not replace for ATP. In the absence of NaF, ATP was ineffective. The phosphorylation of the 160 kDa and/or 150 kDa proteins and the stimulation of Ca2+ efflux are clearly related. The phosphorylation of both proteins and the increase in Ca2+ efflux show a similar dependence on the concentration of ATP. The level of protein phosphorylation and the stimulation of Ca2+ efflux were also controlled by the NaF concentration which inhibits the phosphatase and of net Ca2+ accumulation, as well as for the stimulation of phosphorylation of both polypeptides. Quantitative analysis revealed a linear correlation between these three activities. Dicyclohexylcarbodi-imide, which inhibited Ca2+ efflux, also inhibited the phosphorylation of the two polypeptides. These results suggest the involvement of the phosphorylation/dephosphorylation of 160 kDa and/or 150 kDa polypeptides in the activation of Ca2+ release from SR membranes.

Effects of dibutyryl cyclic AMP, ouabain, and xanthine derivatives on crossbridge kinetics in rat cardiac muscle

In a previous communication, we showed that beta-adrenergic stimulation of cardiac muscles was associated with an increase in the rate of cycling of crossbridges as measured by perturbation analysis in the frequency domain. In this analysis, the frequency at which dynamic stiffness is a minimum (fmin) is taken as a measure of the rate of crossbridge cycling. In this paper, we test the hypothesis that the beta-adrenergic receptor-induced increase in crossbridge cycling rate is mediated by elevation of the intracellular level of cyclic AMP. The approach taken is to compare the effects on fmin in rat papillary muscles during Ba(2+)-activated contractures of 1) an agonist of cyclic AMP that can easily penetrate the cell, namely, dibutyryl cyclic AMP, 2) agents that block cyclic AMP phosphodiesterase, namely, the xanthine derivatives isobutylmethylxanthine and caffeine, and 3) an inotropic agent that does not affect the intracellular level of cyclic AMP, namely, ouabain. Our results showed that dibutyryl cyclic AMP at a dose of 5 mM has the same actions as beta-adrenergic stimulation: it potentiated the isometric twitch force, reduced the time to peak tension and time to half relaxation, and shifted fmin by a factor of 1.8 +/- 0.1 (n = 5). Isobutylmethylxanthine at up to 1.1 mM also acted in the same manner, increasing fmin by a factor of 1.8 +/- 0.2 (n = 6), but ouabain, at a dose (0.03 mM) sufficient to potentiate twitch force by 40 +/- 2% (n = 4), was without effect on the time course of the twitch nor was fmin changed (n = 4). Our findings support the hypothesis that a beta-adrenergic receptor-mediated increase in crossbridge cycling rate is due to an increase in intracellular cyclic AMP level and illustrate the usefulness of the frequency domain analysis approach in the analysis of the mechanism of action of inotropic agents.

Interaction between caffeine intake and heart zinc concentrations in the rat

The purpose of the present study was to determine the levels of zinc in the hearts of growing post-weaning offspring, fetuses and their dams chronically fed caffeine. A further study was conducted to determine the distribution of Zn in subcellular heart fractions affected by acutely injecting caffeine into the veins of the adult rats. After delivery pups were raised on a 200 g protein/kg diet until day 22 of weaning. On day 22 randomly selected male offspring from each litter were divided into two groups. Group 1 was fed continuously on the same diet as a control, whereas in the experimental group offspring were fed on a 200 g protein/kg diet supplemented with caffeine (20 mg/kg). On day 49 the animals were killed and Zn, calcium and magnesium concentrations of the hearts were measured. In the second series of studies pregnant dams were randomly divided into two groups. Group 1 was fed on a 200 g protein/kg diet from day 3 of gestation, whereas in the experimental group dams were fed on the diet supplemented with caffeine. On day 22 of gestation the fetuses were surgically removed. The Zn, Ca and Mg concentrations of hearts of fetuses and dams were determined. In the third phase a caffeine solution was injected into the vein. After 45 min the hearts were removed and Zn levels in the subcellular fractions determined. The hearts of the growing offspring fed on a caffeine-supplemented diet consistently showed decreased Zn and Ca levels compared with the non-caffeine group.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of caffeine on zinc absorption and Zn concentration in rat tissue

The purposes of the present study were to determine whether caffeine has an effect on zinc absorption and tissue levels of Zn. Under anaesthesia, one side of the intestine of female rats was connected to infusion pumps and an infused solution (first caffeine and later Zn solution) was collected from the other side of the intestine using either 300 mm or the whole small intestine to determine Zn absorption. In a further study, different doses of caffeine solution were injected directly into the femoral vein and a saline or Zn solution was infused into the intestine to measure Zn absorption and tissue Zn concentrations. The results consistently showed that the caffeine solution infused into the intestine did not affect intestinal Zn absorption nor was absorption affected by the direct injection of caffeine into the vein. In contrast, injection of different doses of the caffeine solution significantly decreased Zn tissue levels for the heart only. Calcium concentrations in the heart tissue were also decreased, but not magnesium concentrations. Tissue Zn levels recovered immediately on infusion of a Zn solution into the intestine.

High affinity ryanodine binding sites in rat liver endoplasmic reticulum

The binding of [3H]ryanodine to liver microsomal subfractions was investigated. The smooth microsomal membranes were enriched with ryanodine binding sites and also with a polypeptide of 360 kDa. Caffeine completely inhibited [3H]ryanodine binding. Ryanodine also affected the membrane Ca2+ permeability. At low concentrations (less than 10 microM) ryanodine stimulated Ca2+ efflux and at higher concentrations (greater than 50 microM) it blocked Ca2+ efflux. These results suggest that hepatic microsomes contain ryanodine binding sites which can modify the membrane permeability for Ca2+.

Improved resolution of the initial fast phase of heavy sarcoplasmic reticulum Ca2+ uptake by Ca2+:antipyrylazo III dual-wavelength spectroscopy

The effect of ATP upon difference absorbance due to Ca2+ and Mg2+ complexation with the metallochromic dye, Antipyrylazo III (AP III), was investigated. At divalent cation concentrations appropriate for Sarcoplasmic Reticulum Ca2+ transport, wavelengths (greater than 670 nm) were found whereupon the addition of up to 1mM nucleotide did not alter divalent cation:AP III difference absorbance. At these sample wavelengths an initial rapid uptake of Ca2+ by Heavy SR (HSR) was clearly resolved by dual wavelength spectroscopy of Ca2+:dye difference absorbance. Elimination of ATP interference of Ca2+:AP III absorbance by Mg2+ elevation (3-10mM) was shown to be an inappropriate general strategy for AP III spectroscopic studies of HSR Ca2+ transport due to Mg2+ inhibition of ryanodine receptor mediated Ca2+ release.

Activation of the skeletal muscle Ca2+ release channel by the triazine dyes cibacron blue F3A-G and reactive red 120

Vesicle-45Ca2+ ion flux and planar lipid bilayer single-channel measurements have shown that the Ca2+ release channel of skeletal muscle sarcoplasmic reticulum (SR) is activated by micromolar concentrations of Cibacron Blue F3A-G (Reactive Blue 2) and Reactive Red 120. Cibacron Blue increased the 45Ca2+ efflux rate from heavy SR vesicles by apparently interacting with both the adenine nucleotide and caffeine activating sites of the channel. Dye-induced 45Ca2+ release was inhibited by Mg2+ and ruthenium red. In single channel recordings with the purified channel protein complex, Cibacron Blue increased the open time of the Ca2+ release channel without an apparent change in the conductance of the main and subconductance states of the channel.

Polylysine induces a rapid Ca2+ release from sarcoplasmic reticulum vesicles by mediation of its binding to the foot protein

The addition of polylysine to a heavy fraction of sarcoplasmic reticulum (SR) vesicles produces a rapid Ca2+ release with no appreciable lag period. The polylysine concentration for half-maximal activation (C1/2) is approximately 0.99 micrograms/ml, or 0.3 microM, the lowest C 1/2 for Ca2+ release-inducing reagents reported in the literature. The time course and the [Ca2+] dependence of polylysine-induced release are similar to those of caffeine-induced Ca2+ release. At higher concentrations of polylysine (e.g., 10 micrograms/ml), however, little or no Ca2+ release occurs. Upon photolysis of SR vesicles with the photocrosslinkable radiolabeled polylysine derivative, [3H]succinimidyl azido benzoate polylysine, 0.28 and 0.52-1.2 mol polylysine were bound to 1 mol of the 400-kDa foot protein at activating (3 micrograms/ml) and inhibitory (10 micrograms/ml) concentrations of polylysine, respectively. On the other hand, the amounts of polylysine bound to the other SR proteins (mol/mol) were negligible (e.g., less than or equal to 0.0127 mol polylysine/mol calsequestrin). This suggests that the binding of polylysine to the foot protein is responsible not only for the induction of release but also for inactivation. These results provide direct evidence that the receptor for the chemical trigger of Ca2+ release is localized within the foot protein. Ruthenium red, which inhibits polylysine-induced Ca2+ release, does not inhibit polylysine binding to the foot protein, suggesting that the polylysine binding domain of the foot protein is different from the channel domain.

Antibodies to junctional sarcoplasmic reticulum proteins: probes for the Ca2+-release channel

The junctional face membrane plays a key role in excitation-contraction coupling in skeletal muscle. A protein of 350 kDa, tentatively identified as a component of the junctional feet, connects transverse tubules to terminal cisternae of sarcoplasmic reticulum [Kawamoto, Brunschwig, Kim & Caswell (1986) J. Cell Biol. 103, 1405-1414]. The membrane topology and protein composition of sarcoplasmic reticulum Ca2+-release channels of rabbit skeletal muscle were investigated using an immunological approach, with anti-(junctional face membrane) and anti-(350 kDa protein) polyclonal antibodies. Upon preincubation of the terminal cisternae with anti-(junctional face membrane) antibodies, Ca2+-ATPase and Ca2+-loading activities were not affected, whereas anti-(350 kDa protein) antibodies stimulated Ca2+-ATPase activity by 25% and inhibited Ca2+-loading activity by 50% (at an antibody/terminal cisternae protein ratio of 1:1). Specific photolabelling of terminal cisternae proteins with [14C]doxorubicin was prevented by both anti-(junctional face membrane) and anti-(350 kDa protein) antibodies. Stimulation of Ca2+ release by doxorubicin was prevented by both anti-(junctional face membrane) and anti-(350 kDa protein) antibodies. Half-maximal inhibition was obtained at an antibody/terminal cisternae protein ratio of 1:1. Kinetic measurements of Ca2+ release indicated that anti-(350 kDa protein) antibodies prevented Ca2+-induced Ca2+ release, whereas the ATP-stimulation and the inhibition by Mg2+ were not affected. These results suggest that: (i) Ca2+- and doxorubicin-induced Ca2+ release is mediated by Ca2+ channels which are selectively localized in the junctional face membrane; (ii) the 350 kDa protein is a component of the Ca2+-release channel in native terminal cisternae vesicles; and (iii) the Ca2+-activating site of the channel is separate from other allosteric sites.

Inositol 1,4,5-trisphosphate activates a channel from smooth muscle sarcoplasmic reticulum

Inositol 1,4,5-trisphosphate (InsP3) can initiate calcium release into the cytoplasm in a variety of cells. From experiments using permeabilized cells, membrane vesicles, and patch-clamp techniques, it has been suggested that InsP3 acts by directly opening calcium channels. Here, we show that InsP3 induced openings of channels in planar lipid bilayers into which vesicles made from aortic muscle sarcoplasmic reticulum (SR) were incorporated. Activation of channels by InsP3 was not observed when vesicles made from SR of cardiac or skeletal muscle were incorporated into planar lipid bilayers. The present study demonstrates for the first time unique properties of an InsP3-gated calcium channel in sarcoplasmic reticulum vesicles from vascular smooth muscle. This InsP3-activated channel from aortic SR differs strikingly from the calcium-gated calcium channel of striated muscle SR in single-channel conductance and pharmacology.