Il problema delle vene varicose, presentatosi con la prima gravidanza, non è più scomparso e permane tuttora. Alla paziente erano quindi somministrati "Venoruton" e "Arvenum" (sospesi durante le gravidanze) in abbinamento all'utilizzo delle calze elastiche. Dalla diagnosi di insufficienza renale cronica la paziente non assume più i 2 farmaci, tuttavia permane l'utilizzo delle calze elastiche.
La diagnosi di insufficienza renale cronica, dovuta in parte a glomerulonefrite ed in parte ad atrofia tubulare, si evince dall'esito della biopsia renale
Inoltre, a partire dal 2006, la paziente è in cura presso il reparto di nefrologia.
Al fondo di questa pagina, aprendo il file "Modello andamento temporale esami", si possono osservare l'andamento temporale della malattia e il suo decorso clinico dal 2005 ad oggi (grafici inclusi), oltre alla terapia seguita nel corso degli anni.
Dal suddetto allegato si nota che i livelli di creatininemia, potassiemia, fosfatemia e azotemia si sono alzati gradualmente nel tempo, mentre l'emogloblina è calata: tutto ciò indica chiaramente una diminuzione della funzionalità renale nel corso degli anni.
I sopracitati valori sono solo in parte migliorati dall'inizio della dialisi, fermo restando che alcuni parametri restano al di fuori dei normali valori limite.
Inoltre, al fine di una corretta interpretazione riguardo ai valori di emoglobina, si ricorda che la paziente effettua iniezioni di eritropoietina ogni 28 giorni (da dicembre 2010).
Come nota aggiuntiva si ricorda che l'emogasanalisi NON è effettuata su sangue arterioso (così come vorrebbe la regola): il sangue prelevato è sempre stato di origine venosa in quanto era richiesta la sola misurazione della concentrazione di bicarbonati (HCO3-) ematici.
In tal modo la sequenza temporale degli eventi è chiara e il legame con l'età è istintivo.
Nessun problema renale nè cardiovascolare di rilevanza.
Per indagare a fondo il problema la paziente è stata sottoposta ad alcune analisi:
- MTHFR C677T/A1298C risultando eterozigote
- Acido Folico: valori ematici al di sotto della norma
- Omocisteina: valori ematici al di sopra della norma
- Vitamina B12: valori ematici nella norma
- CMV: positiva ad alto titolo per le IgG
- Parvovirus B19: positiva ad alto titolo per le IgG
- Mycoplasma: assenti le Ig
- Chlamydia: assenti le Ig
Occorre però considerare che la paziente è stata sottoposta a trattamento dialitico la sera precedente il prelievo e che quest'ultimo è stato effettuato a digiuno: ciò ha condizionato in parte i valori ematochimici.
A questo punto si possono trarre alcune conclusioni: i fattori causali del danno sono molteplici, così come i fattori predisponenti.
A) PREGNANCY, PRE-ECLAMPSIA AND KIDNEY DISEASE
Initially we have to consider normal and pre-eclamptic pregnancies. Unfortunately, the exactly mechanism of pre-eclampsia is still poor understood even though a lot of studies have been carried out so far. In addiction we have also to consider the immune system. Although discussing the involvment of the immune system and its cytokines in pre-eclampsia is not the aim of this report, they play an important role during both normal and pre-eclamptic pregnancies: the following link is for those who are interested in going into details about this topic (An immunological insight into the origins of pre-eclampsia).
During normal placentation, cytotrophoblast cells form a highly invasive extravillous trophoblast which can migrate into the decidua and invade the first third of the myometrium, leading to spiral arterioles remodelling. This induce the formation of a low-resistance vascular system which allows a 10-fold increase in the blood flow, essential for fetal growth. This mechanism is due to an upregulation of renin angiotensin system (RAS), in fact angiotensin II (AII) can bind to 2 different types of receptors:
- Angiotensin type 1 receptor (AT1R), whose effects are: increased intracellular calcium resulting in vasoconstriction, increased sympathetic activity, sodium and water retention;
- Angiotensin 2 receptor (AT2R), whose effects are: inhibition of cell growth, increased apoptosis, vasodilation and regulation of fetal tissue development.
These two effects are opposite and in normal pregnancy there is a general homeostasys between AT1R and AT2R responses.
By contrast, pre-eclampsia begins early in pregnancy with an inadequate trophoblast invasion, which produces increase in oxidative stress that results in a systemic inflammatory response and contribute to the development of systemic endothelial dysfunction in the later phases of the disease. In addiction RAS dysregulation, occurring in pre-eclampsia, leads to placental hypoxia. Moreover there is heterodimerization of the AT1R (whereas in healthy pregnancies it is monomeric) which is also overactivated by and an increased production of angiotensin II type 1 receptor agonistic autoantibodies (AT1-AA), whose activity are higher than normal pregnancies.
Here there is a table comparing the main differences in RAS factors comparing a normotensive and a pre-eclamptic pregnancies to a nonpregnant woman in order to detect the main differences in RAS factors.
Below the table you can also see how the RAS cascade and the increased levels of AT1-AA lead to several clinical features typical of pre-eclampsia.
Renal, systemic and fetal effects of AT1-AA overactivity have been resumed in the picture below
Briefly, in order to discuss renal effects (see next paragraph), we have to remember that a pre-eclamptic pregnancy is characterized by an increased level of soluble factors (such as sFlt-1 and PAI-1: look at the picture above), Tissue Factor, Reactive Oxygen Species (ROS) and by NADPH oxidase overactivity.
Renin Angiotensin Signaling in Normal Pregnancy and Preeclampsia
Renal Effects
In renal circulation, AT1R overactivation induces important endothelial dysfunctions and general vasocostriction (see the picture above) resulting in increased renal hypoxia. In addiction hyperactivation of AT1R pathway includes increased circulating levels of soluble fms-related tyrosine kinase-1 (sFlt-1), Plasminogen Activator Inhibitor-1 (PAI-1), Tissue Factor (TF) and Reactive Oxygen Species (ROS) (some of them are directly dipendant by NADPH oxydase activation).
Kidney must preserve normoxya as longer as possible, so it responds by increasing Hypoxic-inducible factor 1 alpha (HIF-1α) levels in order to produce, among its products, a larger amount of Vascular Endothelial Growth Factor (VEGF). VEGF is known as the main regulator of blood vessel growth in kidney and plays an important role since it promotes endothelial survival and maintains the microvasculature (Role of vascular endothelial growth factor in kidney disease) by acting in several manners
General hypoxia also contributes to produce angiopoietin 2 (Ang-2) (which is also partially due to HIF-1α pathway), whose bond to Tie2 receptor, brings about destabilization of cell-cell adhesion molecules. (While in normoxya there is a physiological release of Angiopoietin 1 (Ang-1) by the pericytes; so Ang-1 binds to Tie2 receptor and its effect is to transduce the signal for preserving cell-cell adhesion molecules).
Therefore, the gereral kidney homeostasis is lost. In fact, increased binding of VEGF by sFlt-1 and overproduction of Ang-2, lead to endothelial cell apoptosis and vessels destabilization. Moreover, high levels of Ang-2 (but also MCP-1, one of the inflammatory cytokines) are chemoattractive for monocyte-macrophage lineage. We also have to consider permanent activation of NADPH-oxydase whose main outputs are ROS. ROS signalling also gives an overproduction of HIF-1α and others inflammatory cytokines. And, on the other side, chronic endothelium inflammation gives a further push to increase the secretion of pro-inflammatory cytokines secretion, such as Transforming Growth Factor-Beta (TGF-β) and Tumor Necrosis Factor-alpha (TNF-α). Especially TGF-β (but also TNF-α and Ang-2), induces renal fibrosis through epithelial-to-mesenchymal transition (EMT): a process by which epithelial cells acquire mesenchymal characteristics and a migratory phenotype, and secrete molecules associated with extracellular matrix deposition and remodeling. In addiction we have to consider that these effects worsed by raised circulating levels of PAI-1 and by an increased exposure of TF, and the fact that one of HIF-1α target gene is the pro-fibrotic connective tissue growth factor, as well.
Patient's features are progressive kidney damage associated with fibrosis and proteinuria.
The following figure resumes the main effects of excessive TGF-β signaling on kidney cells
In conclusion, although physiological levels of HIF-1α and hypoxia play important roles in keeping renal homeostasis, recent studies show that a disregulation of this system may lead to fibrosis and kidney failure.
The picture below shows the main effects affecting injured nephrons
Angiogenesis and chronic kidney disease
Capillary rarefaction, hypoxia, VEGF and angiogenesis in chronic renal disease
TGF-beta signal transduction in chronic kidney disease
B) MENOPAUSE AND KIDNEY DISEASE
As we know, levels of circulating sex hormones decresase significantly during menopause. In fact, in women, a severe drop of β-Estradiol is registered.
In physiological condition β-Estradiol binds to estrogen receptor (ER), resulting in activation of some different pathways. Among them we have to remember:
- a decrease in expression and activity of the type 1 angiotensin II receptor (AT1R);
- the production of nitric oxide (NO), a gas whose effect is local vasodilatation preserving from ischaemia and, consequently, from hypoxia.
Here it is proposed how the Endothelial Nitric Oxide Synthase (eNOS) is activated by β-Estradiol in order to produce NO
By contrast, during menopause, NO production is lower than normal since β-Estradiol levels decrease. So AT1R activity is increased and there is an increased vasoconstriction. Thus, final result in kidney is hypoxia again with all consequences described above (see the previous paragraph "Pregnancy, pre-eclampsia and kidney disease").
Age-Related Renal Disease in Dahl Salt Sensitive Rats is Attenuated with 17β-Estradiol Supplementation by Modulating Nitric Oxide Synthase Expression
C) GENERAL CONDITIONS PREDISPOSING TO KIDNEY DISEASE
In this paragraph we consider patient's general conditions predisposing to renal failure.
Methylenetetrahydrofolate reductase (MTHFR), Folate, B12 and homocysteine
As we can see in the scanned files above, the patient is heterozygous for both C677T and A1298C and presents:
- low folate levels;
- normal vitamin B12 levels;
- high homocysteine (Hcy) levels.
These clinical features result in an increased incidence of cardiovascular incident associated with hypertensive nephrosclerosis and chronic renal failure.
MTHFR normally catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a cosubstrate for homocysteine remethylation to methionine. As a matter of fact 5-Methyltetrahydrofolate is used for converting homocysteine (Hcy) to methionine by the enzyme methionine synthase which use the cofactor methylcobalamin (MeB12). So, in this metabolic pathway a metilic group (-CH3 ) has been transferred from Homocystein to Methionine.
Thus, deficiency in MTHFR activity and/or in folate and vitamin B12 intake leads to higher levels of Homocysteine. In fact being heterozygous for MTHFR gene is associated with a reduction of enzyme activity, so people who are heterozygous for MTHFR have a thermolabile enzyme with decreased activity at 37°C. In addiction, serum levels of Homocysteine may increase if vitamin B6 (pyridoxine) intake is poor. High levels of homocysteine are associated with cardiovascular disease and Chronic Kidney Disease (CKD). In fact, hyperhomocysteinemia has been involved in endothelial dysfunction, increased oxidative stress and prothrombotic state (inducing clotting factor and inducing platelets aggregation).
Metabolic pathway of hyperhomocysteinemia and its main biological effects on endothelium are shown in this picture
In other words, high homocysteine levels may potentially induce renal injury via direct action on kidney endothelial cells. So, homocysteine can be involved as a cause of renal atherosclerosis and renal damage associated with albuminuria.
Hyperhomocysteinemia is independently associated with albuminuria in the population-based CoLaus study
The MTHFR 677TT and 677CT/1298AC genotypes in Cypriot patients may be predisposing to hypertensive nephrosclerosis and chronic renal failure
Cytomegalovirus
Cytomegalovirus (CMV) belongs to the viral group known as Herpesviridae or herpesviruses, since it is a member of Betaherpesvirinae subfamily. CMV shares with all other herpesviruses the characteristic ability to remain latent within the body over long periods.
CMV primary infections are frequently associated with salivary glands and endothelial cells, but they remain clinically silent. After that, CMV remains in a latent state especially in renal tubular epithelial cells, endothelial cells and salivary glands tubular epithelial cells.
So, we explain the role of CMV in kidney disease.
On the one hand CMV can potentiate renal fibrosis: in fact infected cells develop matrix metalloproteinase-2 (MMP-2), which is important for TGF-β activation in order to promote epithelial-to-mesenchymal transition (EMT) (see the paragraph "Renal Effects" in 1st section "Pregnancy, pre-eclampsia and kidney disease").
Human Cytomegalovirus Induces TGF-β1 Activation in Renal Tubular Epithelial Cells after Epithelial-to-Mesenchymal Transition
On the other hand, CMV infection is linked to hypertension and atherosclerosis, but mechanisms of how viral infection contributes to do this are not defined yet. We know that endothelial cells infection induces renin expression in a non-lytic infectious manner, so it definitely helps in raising arterial blood pressure. Moreover, in mice, endothelial cells infected by CMV increase significantly the expression of pro-inflammatory cytokines like IL-6, TNF-α, and MCP-1 (Monocyte chemoattractant protein-1). The final effect is a higher risk for thrombosis and progressive atherosclerosis in renal circulation with all the consequences described above.
Cytomegalovirus Infection Causes an Increase of Arterial Blood Pressure
Parvovirus B19
Human parvovirus B19 (HPVB19) is a single-stranded DNA virus with a predilection for infecting rapidly dividing cell lines, such as bone marrow erythroid progenitor cells. Nevertheless, HPVB19 can infect all cells exposing P antigen on the surface of the cell membrane, in fact this glycosphingolipid globoside is needed by the virus to bind the cell surface.
Again, we discuss how infection with HPVB19 accouts for kidney disease.
After onset of parvovirus infection, a lot of case reports describe a disease presentation of acute nephritic syndrome with hypocomplementemia often following a prodrome of fever, rash, and arthritis is most common, but nephrotic-range proteinuria is seen, as well. In addiction reported histologic features include endocapillary and/or mesangial proliferation often with subendothelial deposits together with granular deposition of C3 along capillary walls and mesangium.
Since P antigen is exposed on the surface of kidney cells, the following mechanism of cytopathic effects may occur: glomerular cell injury may result from the production of nonstructural viral proteins which have been shown to be cytotoxic. In addiction, deposition of circulating immune complexes that involve viral antigens and host antiviral antibodies could lead to a pattern of injury that is consistent with postinfectious glomerulonephritis. Thus, it can establish the condition of general collapsing glomerulopathy.
Moreover, P antigen has also been demonstrated on surface of endothelial cells so, infection could result in their dysfunction or cell death, leading to capillary thrombosis and glomerular ischaemia.
Therefore, we can consider HPVB19 as a trigger of glomerular disease, in fact its combination with the other factors explained above, can lead to chronic kidney disease.
Parvovirus B19 and the Kidney
D) CONCLUSIONS
In the light of we said, we can support the hypotesis that chronic kidney disease (CKD) has been triggered by several factors, whose effects have been cumulative in the progression of the disease.
Firstly: pre-eclampsia is a predisposing risk factor for endothelial dysfunction, especially in kidney, where this tissue plays an essential role in preserving kidney function. In pre-eclamptic pregnancy there is also an increased production of pro-inflammatory cytokines, soluble factors (whose activity antagonize VEGF and Ang-1 effects), ROS and hypoxia. So, the result is renal fibrosis and scarring via epithelial-to-mesenchymal transition.
Secondly: pre-menopausal and menopausal age could concour to damage kidneys in several manners. Firstly of all, higher NO levels are caused by beta-estradiol production and so we register a drop in estrogens during this period. In addiction, estrogens fall increase the amount of AT1R. So, general results are an increased blood pressure and a progressive endothelial dysfunction.
Lastly, we regard "intrinsic factors", due to genetics, and previous viral infections. A decrease of MTHFR activity, combined with a low level of folate, leads to a raised level in homocysteine, whose consequences are double: on the one hand it causes systemic endothelial damage and on the other hand it can lead to thrombosis as well. Two effects are synergic and result in a systemic cardiovascular disease and progressive renal failure.
Cytomegalovirus and Parvovirus B19 may also contribute to renal injury: since they are tropic for kidney cells, production of toxic proteins and secretion of cytokines, could establish an onset in renal disease which worsed by the previous conditions.
3) Eventuali proposte di terapia, volta al ripristino delle condizioni ottimali
As a matter of fact, patient's therapy started in 2006, when CKD was diagnosed. So, current therapy is described in the attachment named "Modello andamento temporale esami" at the end of this report.
Our aim is to preserve renal functionality before its failure; in other words we want to keep the kidney healthy and avoid CKD condition.
In pre-eclampsia we can administer AT1R blockers in order to decrease oxidative stress levels and endothelial dysfunction, and decrease blood pressure. This way, we can delay renal failure and improve general cardiovascular system (Role of intrarenal angiotensin system activation, oxidative stress, inflammation, and impaired nuclear factor-erythroid-2-related factor 2 activity in the progression of focal glomerulosclerosis).
In menopausal age, we should prescribe a substitutive hormonal therapy in order to reach a gradually reduction in sex hormones hematic levels. As a result, it can preserve renal and cardiovascular system from a sudden change of hormonal homeostasis. Acting through eNOS activation, it can decrease blood pressure and preserve kidney functions.
In addiction, the patient should follow a daily diet rich in folate and B group vitamins by eating an adequate amount of fruits and vegetables, but also animal derived food (important for B12 intake) every day in order to decrease hyperhomocysteinemia, improve MTHFR actinivy and prevent endothelial dysfunction. However this solution must be revised when CKD is detected: in a failed kidney, potassium and phosphate levels are constantly kept under control since the excretion of these electrolytes is lower than normal. In this case the amount of fruit, vegetable and milk derived food eaten every day has to be decreased and B group vitamins may be administered as tablets.
