The role of appendectomy and cholecystectomy in the pathogenesis of colorectal carcinomas.

BACKGROUND: Several alterations in the gastrointestinal tract which occur after appendectomy or cholecystectomy have been suggested to raise the risk of developing colorectal carcinoma. Given the frequency that these procedures are performed, we sought to determine whether a history of either cholecystectomy or appendectomy increased the risk of future colorectal carcinoma. METHODS: We determined the number of patients with a history of appendectomy and cholecystectomy who developed colorectal carcinoma between January 2018 and February 2021, as well as the latency time between the two diseases. Secondly, we carried out a data-collection spanning 15 years after the primary surgery (January 2005-December 2006). RESULTS: The post-cholecystectomy state is significantly more frequently observed in patients treated for colorectal carcinomas (both male and female), especially among those who developed right-sided or left-sided colon cancer, as opposed to anorectal cancer (p = 0.53). However, the time elapsed between the two diseases is 20-25 years, which appears to be markedly long regarding such a multifactorial disease as the colorectal carcinoma. No similar extra risk was observed among patients having appendectomy. Secondly, we found no extra risk during the first 15 years after cholecystectomy. CONCLUSION: Although a statistically higher risk of colon cancer is observed after the removal of the gallbladder, but the latency time is long. Thus, cholecystectomy may not be an independent risk factor for colorectal carcinogenesis. Altogether, the patient is not exposed to a higher risk of colorectal carcinogenesis after having cholecystectomy.

A distinct sequence in the adenine nucleotide translocase from Artemia franciscana embryos is associated with insensitivity to bongkrekate and atypical effects of adenine nucleotides on Ca2+ uptake and sequestration.

Mitochondria isolated from embryos of the crustacean Artemia franciscana lack the Ca(2+)-induced permeability transition pore. Although the composition of the pore described in mammalian mitochondria is unknown, the impacts of several effectors of the adenine nucleotide translocase (ANT) on pore opening are firmly established. Notably, ADP, ATP and bongkrekate delay, whereas carboxyatractyloside hastens, Ca(2+)-induced pore opening. Here, we report that adenine nucleotides decreased, whereas carboxyatractyloside increased, Ca(2+) uptake capacity in mitochondria isolated from Artemia embryos. Bongkrekate had no effect on either Ca(2+) uptake or ADP-ATP exchange rate. Transmission electron microscopy imaging of Ca(2+)-loaded Artemia mitochondria showed needle-like formations of electron-dense material in the absence of adenine nucleotides, and dot-like formations in the presence of adenine nucleotides or Mg(2+). Energy-filtered transmission electron microscopy showed the material to be rich in calcium and phosphorus. Sequencing of the Artemia mRNA coding for ANT revealed that it transcribes a protein with a stretch of amino acids in the 198-225 region with 48-56% similarity to those from other species, including the deletion of three amino acids in positions 211, 212 and 219. Mitochondria isolated from the liver of Xenopus laevis, in which the ANT shows similarity to that in Artemia except for the 198-225 amino acid region, demonstrated a Ca(2+)-induced bongkrekate-sensitive permeability transition pore, allowing the suggestion that this region of ANT may contain the binding site for bongkrekate.

Complex contribution of cyclophilin D to Ca2+-induced permeability transition in brain mitochondria, with relation to the bioenergetic state.

Cyclophilin D (cypD)-deficient mice exhibit resistance to focal cerebral ischemia and to necrotic but not apoptotic stimuli. To address this disparity, we investigated isolated brain and in situ neuronal and astrocytic mitochondria from cypD-deficient and wild-type mice. Isolated mitochondria were challenged by high Ca(2+), and the effects of substrates and respiratory chain inhibitors were evaluated on permeability transition pore opening by light scatter. In situ neuronal and astrocytic mitochondria were visualized by mito-DsRed2 targeting and challenged by calcimycin, and the effects of glucose, NaCN, and an uncoupler were evaluated by measuring mitochondrial volume. In isolated mitochondria, Ca(2+) caused a large cypD-dependent change in light scatter in the absence of substrates that was insensitive to Ruthenium red or Ru360. Uniporter inhibitors only partially affected the entry of free Ca(2+) in the matrix. Inhibition of complex III/IV negated the effect of substrates, but inhibition of complex I was protective. Mitochondria within neurons and astrocytes exhibited cypD-independent swelling that was dramatically hastened when NaCN and 2-deoxyglucose were present in a glucose-free medium during calcimycin treatment. In the presence of an uncoupler, cypD-deficient astrocytic mitochondria performed better than wild-type mitochondria, whereas the opposite was observed in neurons. Neuronal mitochondria were examined further during glutamate-induced delayed Ca(2+) deregulation. CypD-knock-out mitochondria exhibited an absence or a delay in the onset of mitochondrial swelling after glutamate application. Apparently, some conditions involving deenergization render cypD an important modulator of PTP in the brain. These findings could explain why absence of cypD protects against necrotic (deenergized mitochondria), but not apoptotic (energized mitochondria) stimuli.

Forward operation of adenine nucleotide translocase during F0F1-ATPase reversal: critical role of matrix substrate-level phosphorylation.

In pathological conditions, F(0)F(1)-ATPase hydrolyzes ATP in an attempt to maintain mitochondrial membrane potential. Using thermodynamic assumptions and computer modeling, we established that mitochondrial membrane potential can be more negative than the reversal potential of the adenine nucleotide translocase (ANT) but more positive than that of the F(0)F(1)-ATPase. Experiments on isolated mitochondria demonstrated that, when the electron transport chain is compromised, the F(0)F(1)-ATPase reverses, and the membrane potential is maintained as long as matrix substrate-level phosphorylation is functional, without a concomitant reversal of the ANT. Consistently, no cytosolic ATP consumption was observed using plasmalemmal K(ATP) channels as cytosolic ATP biosensors in cultured neurons, in which their in situ mitochondria were compromised by respiratory chain inhibitors. This finding was further corroborated by quantitative measurements of mitochondrial membrane potential, oxygen consumption, and extracellular acidification rates, indicating nonreversal of ANT of compromised in situ neuronal and astrocytic mitochondria; and by bioluminescence ATP measurements in COS-7 cells transfected with cytosolic- or nuclear-targeted luciferases and treated with mitochondrial respiratory chain inhibitors in the presence of glycolytic plus mitochondrial vs. only mitochondrial substrates. Our findings imply the possibility of a rescue mechanism that is protecting against cytosolic/nuclear ATP depletion under pathological conditions involving impaired respiration. This mechanism comes into play when mitochondria respire on substrates that support matrix substrate-level phosphorylation.

A re-evaluation of the role of matrix acidification in uncoupler-induced Ca2+ release from mitochondria.

Massive amounts of Ca(2+) can accumulate in mitochondria, owing to its complexation with matrix phosphate. Under conditions in which the mitochondrial uniporter is the foremost pathway for Ca(2+) efflux, the release of sequestered Ca(2+) by protonophoric uncouplers is invariably demonstrated. This has been recently ascribed to matrix acidification, which results in the dissociation of the Ca(2+)-phosphate complex. In the present study, we compared the effect of stepwise depolarization on Ca(2+) release induced by either the complex III inhibitor stigmatellin or an uncoupler in energized Ca(2+)-loaded rat liver mitochondria in the presence of phosphate, at extramitochondrial pH (pH(o)) 6.8 and pH(o) 7.8. Both poisons were examined in the presence and absence of oligomycin. Prior to Ca(2+) loading, mitochondria were allowed to phosphorylate 0.5 mm ADP. Opening of the permeability transition pore was additionally hampered by cyclosporin A, and was monitored by changes in light scattering. Na(+) was excluded from the medium, preventing Na(+)/Ca(2+) exchange. At both pH(o) values, Delta pH was in the range 0.11-0.15. Complete depolarization by uncoupling with or without oligomycin resulted in an approximately pH 0.05 acidic shift, but there was none in the case of stigmatellin plus oligomycin. At pH(o) 6.8 and in the presence of oligomycin, the uncoupler-induced Ca(2+) release started in the -80 to -50 mV range, whereas in the absence of oligomycin, the release occurred at approximately -15 mV. Stigmatellin induced minor Ca(2+) release only in the presence of oligomycin, starting at approximately -4 mV. At pH(o) 7.8, the uncoupler-induced Ca(2+) release started at approximately -11 mV, irrespective of the presence or absence of oligomycin. Unexpectedly, at this alkaline pH and in the presence of oligomycin, stigmatellin induced substantial Ca(2+) release, starting at approximately -10 mV. From the above findings, we conclude that matrix acidification cannot be the sole explanation for uncoupler-induced Ca(2+) release from mitochondria.

A novel kinetic assay of mitochondrial ATP-ADP exchange rate mediated by the ANT.

A novel method exploiting the differential affinity of ADP and ATP to Mg(2+) was developed to measure mitochondrial ADP-ATP exchange rate. The rate of ATP appearing in the medium after addition of ADP to energized mitochondria, is calculated from the measured rate of change in free extramitochondrial [Mg(2+)] reported by the membrane-impermeable 5K(+) salt of the Mg(2+)-sensitive fluorescent indicator, Magnesium Green, using standard binding equations. The assay is designed such that the adenine nucleotide translocase (ANT) is the sole mediator of changes in [Mg(2+)] in the extramitochondrial volume, as a result of ADP-ATP exchange. We also provide data on the dependence of ATP efflux rate within the 6.8-7.8 matrix pH range as a function of membrane potential. Finally, by comparing the ATP-ADP steady-state exchange rate to the amount of the ANT in rat brain synaptic, brain nonsynaptic, heart and liver mitochondria, we provide molecular turnover numbers for the known ANT isotypes.

Nicotinic acid adenine dinucleotide phosphate (NAADP) and Ca2+ mobilization.

Many physiological processes are controlled by a great diversity of Ca2+ signals that depend on Ca2+ entry into the cell and/or Ca2+ release from internal Ca2+ stores. Ca2+ mobilization from intracellular stores is gated by a family of messengers including inositol-1,4,5-trisphosphate (InsP3), cyclic ADP-ribose (cADPR), and nicotinic acid adenine dinucleotide phosphate (NAADP). There is increasing evidence for a novel intracellular Ca2+ release channel that may be targeted by NAADP and that displays properties distinctly different from the well-characterized InsP3 and ryanodine receptors. These channels appear to localize on a wider range of intracellular organelles, including the acidic Ca2+ stores. Activation of the NAADP-sensitive Ca2+ channels evokes complex changes in cytoplasmic Ca2+ levels by means of channel chatter with other intracellular Ca2+ channels. The recent demonstration of changes in intracellular NAADP levels in response to physiologically relevant extracellular stimuli highlights the significance of NAADP as an important regulator of intracellular Ca2+ signaling.

Ca2+ release triggered by NAADP in hepatocyte microsomes.

NAADP (nicotinic acid-adenine dinucleotide phosphate) is fast emerging as a new intracellular Ca2+-mobilizing messenger. NAADP induces Ca2+ release by a mechanism that is distinct from IP3 (inositol 1,4,5-trisphosphate)- and cADPR (cADP-ribose)-induced Ca2+ release. In the present study, we demonstrated that micromolar concentrations of NAADP trigger Ca2+ release from rat hepatocyte microsomes. Cross-desensitization to IP3 and cADPR by NAADP did not occur in liver microsomes. We report that non-activating concentrations of NAADP can fully inactivate the NAADP-sensitive Ca2+-release mechanism in hepatocyte microsomes. The ability of thapsigargin to block the NAADP-sensitive Ca2+ release is not observed in sea-urchin eggs or in intact mammalian cells. In contrast with the Ca2+ release induced by IP3 and cADPR, the Ca2+ release induced by NAADP was completely independent of the free extravesicular Ca2+ concentration and pH (in the range 6.4-7.8). The NAADP-elicited Ca2+ release cannot be blocked by the inhibitors of the IP3 receptors and the ryanodine receptor. On the other hand, verapamil and diltiazem do inhibit the NAADP- (but not IP3- or cADPR-) induced Ca2+ release.