Effect of temperature on bradykinin-induced arachidonate release and calcium mobilization in vascular endothelial cells

Temperature-sensitive release of prostaglandin E₂ and diminished energy requirements in synovial tissue with postoperative cryotherapy: a prospective randomized study after knee arthroscopy

BACKGROUND

Local external cooling of the surgical field after joint surgery is intended to enhance recovery and to facilitate the use of outpatient surgery by reducing pain and improving mobility. We hypothesized that the effects of postoperative cooling and compression after knee arthroscopy would be reflected in changes in the concentrations of metabolic and inflammatory markers in the synovial membrane.

METHODS

Forty otherwise healthy patients who were to undergo knee arthroscopy were included in the study, and half were randomized to receive postoperative cooling and compression. Microdialysis of the synovial membrane was performed postoperatively, and the concentrations of prostaglandin E₂ (PGE₂), glucose, lactate, glycerol, and glutamate as well as the ethanol exchange ratio (which indicates blood flow) were measured. The temperature of the knee was monitored, and postoperative pain was assessed by the patient with use of a visual analog scale, a numeric rating scale, and the need for rescue medication.

RESULTS

Application of the cooling and compression device after knee arthroscopy significantly lowered the temperature in the operatively treated knee (as measured on the skin, within the joint capsule, and intra-articularly). The cooling and compression appeared to decrease inflammation, as indicated by a temperature-sensitive decrease in the PGE₂ concentration. The hypothermia also decreased the metabolic rate of the synovial tissue and thus decreased energy requirements, as shown by the stability of the lactate concentration over time despite the decreased blood flow that was indicated by the increasing ethanol exchange ratio. No effect of the compression and cooling on postoperative pain was detected.

CONCLUSIONS

Local cryotherapy and compression after knee arthroscopy significantly lowered the temperature in the knee postoperatively, and the synovial PGE₂ concentration was correlated with the temperature. Since PGE₂ is a marker of pain and inflammation, the postoperative local cooling and compression appeared to have a positive anti-inflammatory effect.

Temperature dependence of membrane sealing following transection in mammalian spinal cord axons

Using an in vitro sucrose-gap recording chamber, sealing of cut axons in isolated strips of white matter from guinea pig spinal cord was measured by recording the "compound membrane potential". This functional sealing was found to correlate well with anatomical resealing, measured by a horseradish peroxidase uptake assay. Near-complete functional and anatomical recovery of the axonal membrane occurred routinely within 60 min following transection at 37 degrees C in regular Krebs' solution. The rate of membrane potential recovery is exponential, with a time-constant of 20+/-5 min. The sealing process at 31 degrees C was similar to that at 37 degrees C, and was effectively blocked at 25 degrees C, under which condition most axons continued to take up horseradish peroxidase for more than 1h, and failed to substantially recover their membrane potential. Seventy-five percent of the cords transected at 40 degrees C had similar sealing behavior to those at 37 degrees C and 31 degrees C. The balance failed to seal the cut end. Two-dimensional morphometric analysis has shown that raising the temperature from 25 degrees C to above 31 degrees C significantly decreases axonal permeabilization to horseradish peroxidase (increases the sealing of transected ends) across all areas of a transverse section of spinal cord. Moreover, this enhancement of sealing exists across all axon calibers. Since severe cooling compromises membrane resealing, caution needs to be taken when hypothermic treatment (below 25 degrees C) is applied within the first 60 min following mechanical injury. In summary, we have found that at normal temperature (37 degrees C), nerve fibers repair their damaged membrane following physical injury with an hour. This is similar at mildly lower (31 degrees C) and relatively higher (40 degrees C) temperature, although some fibers tend to collapse under this febrile temperature. Moreover, severely low temperature (25 degrees C) hindered the repair of damaged membranes. Based on our study, caution is needed in treating spinal cord injury with low temperatures.

Temperature dependence of agonist-stimulated Ca2+ signaling in cultured endothelial cells

In cultured endothelial cells, the temperature dependence of bradykinin-initiated Ca2+ signaling was studied using Fura-2 technique. Initially, the temperature dependence of the dissociation constant of Fura-2 for Ca2+ was investigated. Temperature-initiated changes in the apparent dissociation constant (K'D) using the ratio (F340/F380) were due to a hypsochromic shift in excitation wavelengths and changes in the effective dissociation constant of Fura-2 for Ca2+ (K"D). Equations were provided to correct the dissociation constant for Fura-2, either for using the common ratio (F340/F380) or the shift corrected ratio (F340-delta lambda/F380-delta lambda). In a simple experimental protocol, the temperature dependence of the transient increase in free intracellular Ca2+ to bradykinin (i.e. Ca2+ release, sequestration and extrusion) and Ca2+/Mn2+ entry through a Ca2+ store-operated Ca2+ entry pathway (SOCP) were determined. While the temperature dependence of intracellular Ca2+ release, sequestration and extrusion (i.e. enzymatically controlled phenomena) were found to follow the same exponential function [t = A x e(-B x T); t, reaction time; A, B, constants; T, experimental temperature in K; K = degree C + 273], Ca2+/Mn2+ entry upon ion application to pre-stimulated cells strictly followed Fick's law of diffusion [t = A x (1/T) x e(B/T); t, reaction time; A, B, constants; T, experimental temperature in K]. In contrast to the temperature dependence of bradykinin-stimulated Ca2+/Mn2+ entry, the temperature dependence of Mn2+ entry on addition of agonist did not correlate with Fick's law of diffusion, but followed the same exponential function obtained for Ca2+ release, sequestration and extrusion. In conclusion, these data suggest that activation of SOCP by autacoid is due to enzymatic mechanism(s), while Ca2+ entry through SOCP, once activated, is due to a diffusion-like phenomenon.

Effect of temperature on muscarinic cholinoceptor-mediated phosphoinositide metabolism and tension generation in bovine tracheal smooth muscle

The effect of decreased temperature on phosphoinositide metabolism was studied in flurbiprofen pretreated bovine tracheal smooth muscle (BTSM) by investigating the consequences of cooling on muscarinic-cholinoceptor-mediated [3H]inositol phosphate ([3H]InsP) and inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) accumulation, basal phosphoinositidase C (PIC) activity and airways smooth muscle (ASM) tone. Cooling of [3H]Ins labelled BTSM slices from 37 degrees C to 27 degrees C for 20 min prior to the addition of agonist caused a substantial (73.0 +/- 2.5%) inhibition of carbachol (100 microM, 30 min)-stimulated [3H]InsP accumulation compared to values measured at 37 degrees C. The degree of inhibition of [3H]InsP accumulation was similar at all agonist time points (2-30 min) studied. In parallel experiments, cooling of unlabelled BTSM slices from 37 degrees C to 27 degrees C resulted in a 34% reduction in basal Ins(1,4,5)P3 mass (37 degrees C, 13.1 +/- 0.6 pmol mg-1 protein; 27 degrees C, 8.9 +/- 0.9 pmol mg-1 protein; P < 0.02) and markedly attenuated carbachol (100 microM)-stimulated increases in Ins(1,4,5)P3 accumulation. Basal PIC activity in the soluble fraction of BTSM homogenates, measured using a [3H]phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) /deoxycholate assay system, was also significantly lower at 27 degrees C compared to 37 degrees C (initial velocities of PtdIns(4,5)P2 hydrolysis of 853 +/- 167 (37 degrees C) and 418 +/- 119 (27 degrees C) pmol min-1 ml-1 (1/400 diluted) BTSM cytosol; p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)