INTRODUCTION

The renal cortex is formed of glomeruli, proximal convoluted tubules (PCT), cortical portions of loops of Henle, distal convoluted tubules (DCT), and cortical portions of collecting ducts.¹

Statins are the best-tolerated drugs for the treatment of conditions associated with dyslipidemia. They reduce the risk of initial and recurrent cardiovascular events. Rosuvastatin can decrease LDL cholesterol to its normal range and increase HDL cholesterol levels.² Rosuvastatin has many adverse effects on kidneys, liver, and muscles. These side effects are due to reducing serum coenzyme Q10 levels.³

Coenzyme Q10 is usually synthesized through some reactions from mevalonic acid. Mevalonic acid production is inhibited by hydroxyl-methylglutaryl coenzyme A reductase inhibitors. Most of the serum Coenzyme Q10 is bounded to the (LDL) cholesterol.⁴

This study aims to throw light upon the histological changes in the renal cortex of albino rats treated with rosuvastatin and explore the impact of CoQ10 co-treatment.

MATERIAL AND METHODS

Animals:

The study was done at the pharmacology department laboratory of Al-Azhar Faculty of Medicine, Cairo, between August and October 2019.

Experimental design:

Fourty albino rats were divided equally into 5 groups (each group formed of 8 rats) as follows:

Group I: (Control rats) received 1ml isotonic saline /day orally for four weeks.⁵

Group II: (CoQ10 rats) received 1.8 milligrams/Kilogram/day of CoQ10 orally for four weeks.⁶

Group III: (Rosuvastatin rats) received 0.72 milligrams/Kilogram /day of rosuvastatin orally for four weeks.⁷

Group IV: (Rosuvastatin and CoQ10 rats) received 0.72 milligrams/Kilogram/day of rosuvastatin and 1.8 milligrams/Kilogram/day of CoQ10 for four weeks orally.⁶

Group V: (Withdrawal rats) received the same dose of rosuvastatin for four weeks then the rats were sacrificed after the subsequent two weeks.⁸

Chemicals:

Preparation of co-enzyme Q10: “Co-enzyme Q10” capsule 200 mg. Every capsule was dissolved in 200 ml distilled water so every 1ml contained 1mg Co-enzyme Q10.

Preparation of rosuvastatin:  “Rosuvastatin” tablet 40 mg. Every tablet was dissolved in 40 ml distilled water so every 1 ml contained 1 mg of rosuvastatin. The two drugs were purchased from Faculty of Pharmacy, AL-Azhar University, Egypt

At the assigned time, rats were anesthetized using ether inhalation. Blood samples were taken through retro-orbital puncture for measurement of urea and creatinine. The kidneys were carefully dissected. One specimen was prepared and stained with hematoxylin and eosin (H&E) and PAS stains for light microscopic examination.⁹ The other specimen was prepared and stained with a double staining technique of uranyl acetate, followed by lead citrate solutions for electron microscopic examination.¹⁰

RESULTS

Light microscopic findings:

In groups I and group II, the renal cortex consisted of two main parts. It was formed of the renal corpuscles integrated with the renal tubules and minimal interstitium containing peritubular capillaries. The glomerulus was surrounded by the two layers of Bowman’s capsule appeared as the main components of the renal corpuscle. Bowman’s space appeared separating the parietal layer of Bowman’s capsule from the visceral layer. The proximal (PCT) and distal convoluted tubules (DCT) were the main cortical tubules. The nuclei of the PCT and DCT were spherical and centrally located in addition to their cuboidal epithelial lining. The lumen of the DCT was wider and regular due to the absence of the brush border (BB) in the distal tubules (Figures 1,2).

In rosuvastatin-treated rats, most of the renal corpuscles showed small-sized distorted hypercellular glomeruli. The Bowman’s spaces (BS) appeared widened or obliterated. The proximal tubules showed markedly edematous epithelium with severe apoptotic changes. The brush border (BB) of the proximal convoluted tubules (PCT) was partially lost. The distal convoluted tubules (DCT) appeared with intraluminal debris and severely congested interstitial blood vessels. Intratubular vacuolation with granular casts was seen. Congestion of blood vessels with areas of hemorrhage was seen in the renal cortex (Figure 3).

In groups IV&V, the histological architecture of the glomerulus, PCT, and DCT returned to the normal histology detected in the control group (Figure 4,5).

Electron microscopic findings:

Groups I and II revealed the normal histology of the glomerular capillaries which was formed of three layers arranged from outside as follows: podocytes, glomerular basement membrane (GBM), and fenestrated endothelium.

The PCT showed large nuclei which were spherical, basally located, and euchromatic with prominent nucleoli. The cytoplasm showed mitochondria with cristae, dense long micro-villi, normal (BB), and normal basal lamina.

The DCT showed cells with few short microvilli, round centrally located nuclei with central nucleoli and condensed chromatin in the periphery, normal mitochondria, and basal infoldings (Figures 6,7).

The podocytes showed two cytoplasmic processes. The primary and secondary foot processes of the podocyte appear close to the GBM. The GBM was uniform in thickness (Figure 8).

Group III rats showed loss of the glomerular architecture with an irregular basement membrane, podocyte with an irregular nucleus, marked effacement of foot processes, and very narrow filtration slits.

The PCT in group III showed wide lumen with few long microvilli, basally located heterochromatic markedly pyknotic nuclei with prominent nucleoli, swollen mitochondria, scattered cytoplasmic vacuoles, and thickened basal lamina.

The DCT in group III showed few short microvilli, centrally located heterochromatic markedly pyknotic nuclei with centrally located nucleoli, swollen mitochondria, and intra-luminal debris obliterating most of the lumen (Figures 9-11).

Groups IV and V showed the normal structure of the glomerular capillaries, PCT, and DCT (Figures 12-14).

Fig.1: A photomicrograph of Hematoxylin and Eosin section (group I), showing rounded glomeruli (G), each is surrounded by the two layers of Bowman’s capsule with Bowman’s space (BS). In addition to glomeruli, the cortex consisted mainly of PCT (PT), and DCT (DT). The PCT has highly defined brush borders (arrowhead) with a normal basement membrane. (H&E. X360).

Fig. 2: A photomicrograph of Hematoxylin and Eosin section (group II), showing renal corpuscles formed of a glomerulus (G) in addition to the PCT (PT) and DCT (DT). Proximal tubules show normal epithelial lining with normal brush borders (yellow arrow), and normal BM (black arrows) (H&E. X360).

Fig. 3: A photomicrograph of Hematoxylin and eosin section (group III), showing small-sized distorted glomerulus (G) and average Bowman’s space. The PCT shows massive cellular edema and dilated lumen with apoptosis of its epithelial lining (black arrow). The brush borders of the PCT are completely lost with intra-tubular debris (red arrows) and intra-tubular granular casts (yellow arrow) (H&E. X360).

Fig. 4: A photomicrograph of PAS section (group IV) showing normal glomerulus (G), the brush borders of the PCT appear normal (yellow arrows) but he black arrow points a PCT with lost BB. Most of the DCT (DT) are normal (PAS. X360).      

Fig. 5: A photomicrograph of Hematoxylin and eosin section (group V) showing the normal renal corpuscle formed of a glomerulus (G) surrounded by the two layers of Bowman’s capsule with Bowman’s space. The PCT (PT) and DCT (DT) appear completely normal. Many tubules show normal epithelium (black arrows). Some capillaries appear dilatated and congested (yellow arrows) (H&E. X360).

Fig. 6: An electron micrograph of the DCT (group I) revealing cells with few short microvilli (MV), Golgi apparatus (G), round centrally located nuclei (N) with central nucleoli and condensed chromatin in the periphery, normal mitochondria (M), and basal infoldings (TEM X10000). 

Fig. 7: An electron photomicrograph of the PCT (group I). It shows basally located rounded euchromatic nuclei (N) with prominent nucleoli (red arrow). The cytoplasm showing mitochondria with normal cristae (M), dense long microvilli forming a fantastic (BB), and intact basement membrane (BM) (TEM X5000).

Fig. 8: An electron photomicrograph of the glomerulus (C) (group II) showing normal glomerulus with intact basement membrane (BM), Mesangial cell, normal Podocyte (P), and its primary foot processes with patent filtration slits (FS). RBC= Red blood cell.(TEM X25000).

Fig. 9: An electron photomicrograph of the PCT (group III), showing shrunken nuclei with loss of their heterochromatin (red arrows). Intraluminal epithelial debris (LCD) can be seen. The apical microvilli are lost (white arrow). The basal lamina is interrupted (blue arrow). The mitochondria are swollen and edematous (M). BC= blood capillary (TEM X3000).

Fig. 10: An electron photomicrograph of the DCT (group III), showing intraluminal cellular debris (LCD) with a widened lumen (L). The apical microvilli are completely lost (Black arrow). Most of the nuclei are small-sized (N1) and irregular. Multiple vaculations are seen within the cytoplasm (Blue arrow). Note the swelling and edema of the mitochondria (M) with congestion and dilatation of blood vessels (BV) (TEM  X4000).

Fig. 11: An electron photomicrograph of the glomerulus (C) (group III), showing distorted glomerulus with irregular basement membrane (black arrow). The podocytes (P) show marked effacement of its processes (yellow arrow) with a very narrow filtration slit (FS) (TEM  X25000).

Fig. 12: An electron photomicrograph of the renal cortex (group IV), showing intact GBM, normal appearance of the proximal convoluted tubule (blue arrow), and normal podocyte with its processes (P). The blood capillaries are mildly dilated (BC) (TEM X3000).

Fig. 13: An electron photomicrograph of the DCT (group IV) showing few short microvilli (red arrow), centrally located round nuclei (N) with central nucleoli and condensed chromatin in the periphery, scattered vacuoles and basal infoldings (black arrow). L=lumen(TEM X10000).

Fig. 14: An electron photomicrograph of the PCT (group V), showing spherical nucleus (N), peripherally located chromatin, and normal (BB). The mitochondria appear normal (M) (TEM X5000).

Biochemical results:

By using the analysis of variance (ANOVA) and the least significant difference (LSD) tests, serum urea and creatinine showed a significant increase in the rosuvastatin-treated group. The biochemical results in groups IV and V were similar to that of group I (figure 15) (tables 1-3).

Table 1:  Comparison between the mean urea using the ANOVA test (analysis of variance).

Table 2: Comparison between the mean creatinine using the ANOVA test.

Table 3: Comparison between the biochemical results in the different studied groups using the least significant difference (LSD).        

Fig. 15: Comparison between the mean urea and creatinine.

Statistical results:

By using one way ANOVA test, a significant increase in the rosuvastatin-treated group (p-value