Mecanismos moleculares implicados en el daño renal agudo por rabdomiolisis

Abstract

Acute kidney injury (AKI) is the abrupt decrease in kidney function, which encompasses both injury and impairment. The 7-10% of AKIs are caused by rhabdomyolysis, a syndrome characterized by the rupture of skeletal muscle and massive release of myoglobin into the bloodstream, resulting in increased renal injury. Currently there is no specific pharmacological treatment for this pathology, only palliative care, so the search for new mechanisms involved in the development of this phenomenon is of great interest. Klotho is a protein that is expressed mainly in the kidney and has anti-inflammatory and antioxidant actions, in addition to being involved in the homeostasis of phosphorus and calcium. Klotho's renal expression decreases in contexts of oxidative stress and inflammation. These two conditions occur during rhabdomyolysis associated AKI. In this thesis we have studied the physiopathological mechanisms involved in renal damage by rhabdomyolysis, with special interest in Klotho's renal expression. To this end, we have developed several experimental approaches in rhabdomyolysis models in mice and we have performed studies on tubular cells stimulated with myoglobin. In addition, we have tested Klotho's plasma levels in patients with rhabdomyolysis. Our data show that induction of rhabdomyolysis in mice decreases renal function, causes hyperphosphatemia, hypocalcemia, and increases tubular damage and oxidative stress at 24h, with gradual improvement of these parameters at 3 and 7 days. Inflammatory cytokine expression increased at 24 h, observing macrophage infiltration at 3 and 7 days. Our in vivo results show a significant decrease in Klotho's gene expression in the kidney from 3h and in protein from 24h which was still reduced at 30 days, coinciding with an increase in renal fibrosis and a chronic inflammatory response. We observed a decrease in Klotho plasma levels in patients with rhabdomyolysis associated AKI. In tubular cells stimulated with myoglobin, we observed an increase in oxidative stress and inflammatory mediators, as well as a dose dependent decrease in Klotho mRNA and protein expression of Klotho. The decrease of Klotho by myoglobin was reversed with the use of antioxidants and Nrf2 activators in vitro, but not in vivo. Finally, our data show that Klotho plays an important role in the prevention of kidney damage by rhabdomyolysis, since the exogenous administration of recombinant Klotho improved renal function and reduced the expression of markers of tubular damage. In conclusion, our results show that rhabdomyolysis-associated AKI reduces Klotho's renal expression early, which remained reduced even when renal function has been restored. The decrease of Klotho in rhabdomyolysis may be related to oxidative stress, although it is not the main mechanism responsible.