Animal toxins and renal ion transport: Another dimension in tropical nephrology

Heparin prevents the cytotoxic activity of Bothrops jararacussu and Apis mellifera venoms in renal cells

Envenomation by Bothrops snakes and Apis mellifera bee may imply systemic disorders which affect well-perfused organs such as kidneys, a process that can lead to acute renal failure. Nevertheless, there is scarce information regarding a direct renal cell effect and the putative antagonism by antivenoms. Here the cytotoxic effect of B. jararacussu and A. mellifera venoms was evaluated in the renal proximal tubule cell line LLC-PK1, as well as the antagonism of this effect by heparin. B. jararacussu venom showed significant cytotoxicity as assessed by LDH release and MTT reduction, with a sharp decline of the cell number after 180 min (>90% at 50 μg/mL). A. mellifera venom produced a much faster and potent cytotoxic activity, conferring almost no viable cells after 15 min at 25 μg/mL. Phase contrast microscopy revealed that while B. jararacussu venom induced a progressive loss of cell adhesion and detachment, A. mellifera venom promoted a rapid plasma membrane disruption and nuclear condensation suggestive of necrotic cell death. Pre-incubation of both venoms with heparin for 30 min significantly reduced cytotoxicity. Our results demonstrate direct toxicity of B. jararacussu and A. mellifera venoms toward renal cells but with distinct kinetics and cell pattern, suggesting different mechanisms of action. In addition, the antagonistic, cytoprotective effect of heparin ascribes such compound as a promising drug for preventing renal failure from envenomation.

Regulation of Electrolyte Permeability by Herbal Monomers in Edematous Disorders

Edema is a gradual accumulation of fluid in the interstitial tissues or luminal cavities, which is regulated by ion transport pathways and reflects dysfunction of fluid and salt homeostasis. Increasing evidence suggests that some herbal monomers significantly reduce organ/tissue edema. In this review, we briefly summarized the electrolyte permeability involved in pathomechanisms of organ edema, and the benefits of herbal monomers on ionic transport machinery, including Na+-K+-ATPase, Na+ and Cl- channels, Na+-K+-2Cl- co-transporter, etc. Pharmaceutical relevance is implicated in developing advanced strategies to mitigate edematous disorders. In conclusion, the natural herbal monomers regulate electrolyte permeability in many edematous disorders, and further basic and clinical studies are needed.

Centruroides margaritatus scorpion complete venom exerts cardiovascular effects through alpha-1 adrenergic receptors

Centruroides margaritatus scorpion stings are common in Colombia. However, the cardiovascular toxicity of the venom has not been clarified.

AIM

To study the effect and mechanisms of action of the complete venom of C. margaritatus (CmV) on the murine cardiovascular system.

METHODS

We evaluated the in vivo effect of CmV LD50 on the mean arterial pressure (MABP), heart rate, and surface electrocardiogram in male adult normotensive Wistar rats. Ex vivo, we evaluated the vascular reactivity of rat aortic rings to increasing concentrations (1 to 60 μg/mL) of CmV using the blockers L-NAME, indomethacin, seratrodast, and prazosin.

RESULTS

In the first hour of poisoning, CmV increased the MABP. In the second hour after poisoning, the heart rate decreased as the normalized PR interval and QT corrected increased. After that, cardiovascular shock was demonstrated by a drastic fall in the MABP and signs of cardiac conduction system block. In aortic rings, CmV caused a direct vasoconstrictor effect mediated by alpha-1 adrenergic receptors and counteracted by nitric oxide.

CONCLUSION

The direct vascular and probably the cardiac alpha-1 effects likely explain the transient hypertension and the maintenance of cardiac function, while interval lengthening may be due to K+ channel blockage. Afterwards, the effects of both the alpha-1 pathway and the K+ channel pathway converged, resulting in fatal cardiovascular shock. This knowledge could aid in understanding the dynamics of the effects of the venom and in designing treatments to address its cardiovascular effects.

Renal Alterations Induced by the Venom of Colombian Scorpion Centruroides Margaritatus

BACKGROUND

Scorpion venom causes renal injury and affects vascular ion-channels function. Centruroides margaritatus scorpion is found in Colombia and is frequently the cause of envenomation accidents; however, its renal impact has never been investigated.

OBJECTIVE

To evaluate the effects of C. margaritatus venom (CmV) on renal parameters using isolated rat kidney and renal cell culture models.

METHODS

Wistar rats (n = 5, weighing 240-300 g) were first perfused with Krebs-Henseleit solution containing 6 g 100 mL-1 bovine serum albumin. After 30 minutes, the kidneys were perfused with CmV to a final concentration of 10 μgmL-1; evaluation was performed by measuring Perfusion Pressure (PP), Renal Vascular Resistance (RVR), Urinary Flow (UF), Glomerular Filtration Rate (GFR), and percentage of electrolyte tubular transport. Moreover, kidney histological analyses and cell cytotoxicity in renal tubule epithelial cells (MDCK) and proximal tubular cells (LLC-MK2) were assessed.

RESULTS

CmV increased PP and RVR 60 min after perfusion. On the other hand, UF, GFR, and the percentages of sodium, potassium and chloride tubular transport decreased after experimental envenomation. UF dropped after 120 min, while GFR and percentage of electrolyte tubular transport diminished after 60, 90 and 120 min. CmV was not toxic to MDCK cell line but reduced the viability of LLC-MK2 cells at concentrations ranging from 6.25 to 200 μgmL-1. Histological analyses disclosed hydropic degeneration, edema, and protein deposits. Flow cytometry disclosed that cell death occurred predominantly by necrosis.

CONCLUSION

Our results suggest that C. margaritatus venom can trigger renal impairment, mainly in the proximal kidney tubule.