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 ~~~  CELLULAR  PHYSIOLOGIC  CONTROL  MECHANISMS  ~~~
		1.  GROWTH  FACTORS 
		2.  CYTOKINES 
		3.  CYCLIC  AMP  or  GMP 
		4.  CALMODULIN 
		5.  NITRIC  OXIDE 
		6.  DOCOSOIDS 
		7.  PROTEIN  PHOSPHORYLATION 
		8.  NUCLEAR  BINDING  OF  STEROIDS 
		9.  ***  REDOX  STATUS  *** 

	~~~  ANTIOXIDANT  ADAPTATION  ~~~
	Prooxidant conditions trigger the induction 
	of various antioxidant enzymes such as:
		- glutathione reductase
		- glutathione synthase
		- glutathione peroxidase
		- superoxide dismutase
		- catalase
	Temporary prooxidant conditions if not beyond 
	the organism's ability to resist and adapt will:
		- redistribute reducing equivalents
		    passively and actively
		- enhance resistance to oxyradical damage
		- inhibit pathology dependent syntheses

	~~~  ENZYMATIC  OXYRADICAL  QUENCHING  ~~~
Superoxide Dismutase: 
	-OO* +  Enz (Cu++)  -->  O2  +  Enz (Cu+) 
	-OO* +  Enz (Cu+)  +  2 H+  --> H2O2  + Enz(Cu++)
Catalase: 
	2H2O2 + Enz (Fe) --> O2 + H2O + Enz (Fe) 
Glutathione Peroxidase: 
	2 GSH  +  HOOH --> GSSG  +  2 HOH 
	2 GSH  +  LOOH  --> GSSG + LOH + HOH 

~~~ REDOX CONTROL OVER OXY-HEMOGLOBIN DISSOCIATION ~~~
Reduced glutathione (GSH) is converted to the 
    disulfide (GSSG) by the action of oxyradicals 
    and by glutathione peroxidase. 
The presence of elevated levels of GSSG triggers a 
    change in glucose metabolism in an effort to shift 
    the utilization of hydrogen towards GSSG reduction. 
This change results indirectly in higher levels 
    of 2,3-diphosphoglycerate (2,3-DPG). 
2,3-DPG attaches to oxyhemoglobin in such a way as to 
    enhance dissociation or release of diatomic oxygen. 
Thus mildly pro-oxidant conditions enhances 
    the delivery of diatomic oxygen to tissues. 


~~~   OXIDATIVE  RESCUE  OF  CYTOCHROME  A   ~~~
To review a list of known toxic agents produced 
    by the putrifying action of colonic anaerobes, 
    one of the most toxic is hydrogen sulfide (H2S). 
Similar to cyanide (CN-), carbon monoxide (CO), and 
    azide (NN-) the bisulfide anion (HS-) attaches 
    to the copper of cytochrome a3 as a ligand. 
This shuts down the action of an entire respiratory 
    electron transport chain. 
This also results in failure to phosphorylate ADP, 
    plus a rapid and profound accumulation of reductants. 
Pro-oxidant conditions, however, can increase 
    the RSSR' / RSH ratio. 
All disulfides readily absorb hydrogen sulfide. 
        R'SSR" +  HSH  --->  R'SSH  +  HSR" 
Thus a hypothetical mechanism of H2S detoxification, 
    rescue of mitochondrial phosphorylation, 
    and restoration of normal redox potentials 
    should result from treatment with oxidants. 

~~~  REDOX  CONTROL  OVER  LEUKOTRIENE  SYNTHESIS  ~~~
Leukotrienes are long acting promotors of inflammation.
Many of these are produced by combining glutathione
    with certain proinflammatory docosoids.
Oxidation of reduced glutathione hypothetically 
    inhibits this process.
This opens the possibility for mildly oxidizing conditions 
    to have significant antiinflammatory effects.

	~~~   MECHANISM   OF   GLYOXALASE   ~~~
Reduced glutathione acting as a nucleophile spontaneously
adds to methylglyoxal producing a thiohemiacetal.
                  O  O                OH O
       G-S-H  +  HC--C--CH3  -->  G-S-C--C--CH3
                                      H
Glyoxalase I tautomerizes the thiohemiacetyl as shown.
                  OH O                O  OH
              G-S-C--C--CH3  -->  G-S-C--C--CH3
                  H                      H
Glyoxalase II hydrolyses the alpha-hydroxy-acyl product
of glyoxalase I yeilding reduced glutathione and lactic acid.
          O  OH                                O  OH
      G-S-C--C--CH3  +  HOH  -->  G-S-H  +  H0-C--C--CH3
             H                                    H

	~~~   REDOX  CONROL  OF  GLYOXALASE   ~~~
Methylglyoxal was discovered by Albert Szent-Gyorgyi, 
    et al, to be a physiologic inhibitor of cell division. 
Its level is controlled by the enzyme "glyoxalase", 
    which converts methylglyoxal to lactic acid. 
However, glyoxalase requires reduced glutathione 
    (GSH) as a cofactor. 
Oxidation of glutathione inhibits the action 
    of glyoxalase. 
As the levels of methylglyoxal rise proliferation 
    is inhibited. 

	~~~  REDOX  CONTROL  OF  ENZYMATIC  FUNCTION 
		BY  THIOL / DISULFIDE  CONVERSION  ~~~
The ease of conversion of thiols to disulfides by oxidation, 
	RSH + R'SH + [O] ---> RSSR' + H2[O] 
And the ease of reversion of disulfides 
back to thiols by reduction, 
	RSSR' + 2[H] ---> RSH + R'SH 
Provide an important mechanism for physiologic control. 
Many enzymes which depend upon a cysteine residue 
    at the active center or as part of the structure 
    can be switched to the [OFF] mode by oxidation.
This may result in an autogenous disulfide 
    or the attachment of an exogenous sulfide.

	gly     [ON]                 gly     [OFF]
	ala                          ala
	cys--S--H + RSH + [O]  --->  cys--S--S--R + H[O]H 
	thr                          thr
	phe                          phe

	~~~  ORNITHINE  DECARBOXYLASE  ~~~
Ornithine decarboxylase (ODC) is an enzyme, 
    which is induced in all proliferating cells. 
ODC converts ornithine (an amino acid) to putrescine, 
    an essential intermediary in polyamine synthesis. 
		NH2--CH2--CH2--CH2--CH2--NH2 
ODC has a cysteine residue, necessary to its function, 
    which is maintained in the reduced state by other thiols. 
The thiol group of ODC is sensitive to oxidation, 
    and such oxidation inactivates this enzyme. 
Prooxidant conditions therefore temporarily inhibit ODC 
    activity and polyamine dependent cell proliferation. 

~~~  REDOX  CONTROL  OF  POLYAMINE  FUNCTION  ~~~

REDUCTION  FAVORS: 
	Ornithine Decarboxylase Activation 
	Polyamine Synthesis 
	Polyamine Preservation 
	Growth And Proliferation 

OXIDATION  FAVORS: 
	Ornithine Decarboxylase Deactivation 
	Inhibition Of Polyamine Synthesis 
	Oxidative Conversion To Aldehydes 
	Inhibition Of Growth And Proliferation 

"REDOX SIGNALING AND THE CONTROL OF CELL GROWTH AND DEATH" 
Advances In Pharmacology [series], 
Volume 38, pp 329-359, Academic Press, 1997 
	by Garth Powis, John Gasdaska, Amanda Baker 
at Arizona Cancer Center, University of Arizona, Tucson 
CONTENTS: 
I.  oxidation-reduction as a physiologic control mechanism 
II. cellular redox systems: glutathione, thioredoxin, 
            protein disulfide isomerase, glutaredoxin, 
            Ref-1, metallothionein 
III.redox targets: ribonucleotide reductase, 
            receptor proteins, transcription factors: 
            OxyR, NFkB, AP-1, p53, kU, v-Ets, E2, Ah, 
            protein folding & degradation 
IV. cellular responses to redox changes: 
            proliferation, thioredoxin activity, 
            oxidant signaling and apoptosis, 
            oxidative stress, hypoxia 
Bibliography contains 204 references. 

	~~~  REDOX  ACTIVE  PROTEIN  THIOLS  ~~~
"Thioredoxin" (Trx) is a low molecular weight protein 
  baring two closely situated cysteine residues, 
  which offer two redox active thiol groups. 
In vivo Trx redox cycles between its reduced dithiol 
  form Trx-(SH)2 and its oxidized disulfide form Trx-SS. 
        Trx-(SH)2  +   [O]   --->   Trx-SS   +   H[O]H 
        Trx-SS    +   2[H]   --->   Trx-(SH)2 
The flavoprotein "thioredoxin reductase" utilizes 
  reducing equivalents from NADPH to maintain Trx 
  in the reduced state. 
        NADPH ... FAD / FADH2 ... Trx-SS / Trx-(SH)2 
Protein thiols such as Trx, protein disulfide isomerase 
  (PDI), and Ref-1 are important intracellular carriers 
  of hydrogen atoms. 
These in turn maintain various other proteins in the 
  reduced state, and maintain certain oxidant sensitive 
  enzymes, growth factors, and transcription factors 
  in the active state. 
Activator-Protein-1 (AP-1) is a transcription factor 
  and is activated by thiol proteins as follows: 
        NADPH ... FAD/FADH2 ... Trx-SS/Trx-(SH)2 ... 
        ... Ref-1-SS/Ref-1-(SH)2 ... AP-1-SS/AP-1-(SH)2 
Reduced Trx also serves to convert 
  ribonucleoside-5'-diphosphates to 
  deoxyribonucleoside-5'-diphosphates. 
        RNPP-OH + Trx-(SH)2 ---> dRNPP-H + Trx-SS + H2O 
The redox sequence is as follows: 
        NADPH ... FAD/FADH2 ... Trx-SS/Trx-(SH)2 ... 
        RNPP-OH/dRNPP-H 
Glutaredoxin (Grx) performs the same role as thioredoxin 
  (Trx), however, Grx must accept hydrogen from 
  glutathione (GSH). 
        NADPH ... FAD/FADH2 ... GSSG/GSH ... 
        Grx-SS/Grx-(SH)2 ... RNPP-OH/dRNPP-H 
Thus reductants as supplied by NADPH and carried 
  by thiol proteins are necessary for a variety 
  of proliferation related functions. 

	~~~  TRIGGERING  OF  APOPTOSIS  ~~~
Apoptosis (programmed cell death) is a normal 
  physiologic process whereby certain cells 
  are selected for self-destruction.
This may occur as a part of embroyologic 
  developement or as a mechanism to remove aged,
  damaged, or malfunctioning cells.
A beneficial result would be the termination
  of IgE producing plasma cells or tumor cells.
One of the physiologic triggers of apoptosis
  is an oxidant sensing mechanism.
When successful such apoptosis can produce long 
  term beneficial results from oxidative therapies.

	~~~  P53  PROTECTOR  OR  ONCOGENE?  ~~~ 
P53 stands for the genome and corresponding 
  protein involved in several control systems: 
   -- detection of DNA damage 
   -- initiation of DNA repair 
   -- promotion versus suppression of proliferation 
   -- initiation of apoptosis by oxidants, etc. 
Healthy P53 protein has cysteine residues, 
  which are sensitive to oxidation, making 
  redox control part of normal P53 function. 
Mutation(s) of the P53 genome in favor 
  of carcinogenesis result in: 
   -- promotion function locked  
   -- apoptosis function locked  
   -- sensitivity to oxidants decreased or absent 

~~~ REDOX CONTROL OVER IMMUNOLOGIC TRIGGER MECHANISM ~~~
Most redox sensitive enzymes and transcription factors are 
  inhibited upon oxidation and reactivated upon reduction. 
Conversely, certain other enzymes (namely protein kinases) 
  are activated upon oxidation and inhibited upon reduction. 
A wide variety oxidants (including ultraviolet light 
  and GSSG), can activate specialized protein kinases 
  in immune cells. 
Immune cells have protein complexes composed of 
  "inhibitor kappa B" and "nuclear factor kappa B". 
Activated protein kinases phosphorylate I-kappa-B. 
Ubiquitin attaches to phosphorylated proteins. 
The proteosome subsequently eliminates I-kappa-B 
  by digestion. 
NF-kappa-B is released and migrates to the nucleus. 
There it associates with the transcription protein AP-1. 
Messenger RNA is synthesized which in turn 
  directs the ribosomes to produce cytokines. 
Cytokines function as alarms which trigger activation 
of systemic immunity. 

~~~  GSSG  AS  COFACTOR  IN  IMMUNOACTIVATION  ~~~
In many types of cells oxidants can directly 
  activate protein kinases without involving GSSG. 
However, in certain immune cells GSSG is a 
  necessary cofactor to protein kinase activation. 
In these cells, deficiency of GSH and/or GSSG 
  results in failure of NFKB transactivation. 
This explains how glutathione deficiency is 
  associated with immune dysregulation. 

~~~  INHIBITION  OF  HISTAMINE  RELEASE  ~~~
Histamine is a proinflammatory agent produced 
    by the enzymatic decarboxylation of histidine. 
Histamine is stored in granules within mast cells. 
Mast cells degranulate and release histamine 
    upon action of IgE-antigen complexes. 
The release of histamine from mast cells is inhibited 
    by certain enediols such as: ascorbic acid, 
    quercetin, and other polyphenolic bioflavonoids. 
Which phase (oxidized or reduced) of the enediol 
    compound is actually responsible for this 
    inhibition remains to be clarified. 

~~~ REVIEW OF PHYSIOLOGIC EFFECTS OF OXIDANT EXPOSURE ~~~
1.  Passive and active redistribution of reducing 
    equivalents towards oxidant eliminating pathways.
2.  Adaptive induction of oxyradical quenching enzymes. 
3.  Enhanced oxyhemoglobin dissociation.
4.  Temporary detoxification of hydrogen sulfide. 
5.  Inhibition of leukotriene synthesis.
6.  Inhibition of glyoxalase.
7.  Reversible inhibition of numerous enzymes 
    and physiologic triggers which utilize thiols 
    in their active centers.
8.  Initiation of apoptosis in unwanted cells.
9.  Induction of cytokine expression. 
10. Modulation of histamine release.
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