Level of activation of the unfolded protein response correlates with Paneth cell apoptosis in human small intestine exposed to ischemia/reperfusion.
OBJECTIVE
In the intestine, Paneth cells participate in the innate immune response. Their highly secretory function makes them susceptible to environmental conditions that cause endoplasmic reticulum (ER) stress. We investigated whether intestinal ischemia/reperfusion (I/R) induces ER stress, thereby activating the unfolded protein response (UPR), and whether excessive UPR activation affects Paneth cells. In addition, we investigated the consequences of Paneth cell compromise during physical barrier damage.


METHODS
Jejunal I/R was studied using a human experimental model (n = 30 patients). Activation of the UPR was assessed using immunofluorescence for binding protein and quantitative polymerase chain reaction analyses for C/EBP homologous protein (CHOP), growth arrest and DNA-damage inducible protein 34 (GADD34), and X-box binding protein 1 (XBP1) splicing. Paneth cell apoptosis was assessed by double staining for lysozyme and M30. Male Sprague-Dawley rats underwent either intestinal I/R to investigate UPR activation and Paneth cell apoptosis, or hemorrhagic shock with or without intraperitoneal administration of dithizone, to study consequences of Paneth cell compromise during physical intestinal damage. In these animals, bacterial translocation and circulating tumor necrosis factor-α and interleukin-6 levels were assessed.


RESULTS
In jejunum samples from humans and rats, I/R activated the UPR and resulted in Paneth cell apoptosis. Apoptotic Paneth cells showed signs of ER stress, and Paneth cell apoptosis correlated with the extent of ER stress. Apoptotic Paneth cells were shed into the crypt lumen, significantly lowering their numbers. In rats, Paneth cell compromise increased bacterial translocation and inflammation during physical intestinal damage.


CONCLUSIONS
ER stress-induced Paneth cell apoptosis contributes to intestinal I/R-induced bacterial translocation and systemic inflammation.
Department of Surgery, NUTRIM School for Nutrition, Toxicology & Metabolism, Maastricht University Medical Center, Maastricht, The Netherlands.
Joep
J
Grootjans
Caroline M
CM
Hodin
Jacco-Juri
JJ
de Haan
Joep P M
JP
Derikx
Kasper M A
KM
Rouschop
Fons K
FK
Verheyen
Ronald M
RM
van Dam
Cornelis H C
CH
Dejong
Wim A
WA
Buurman
Kaatje
K
Lenaerts
D000818:Animals; D000943:Antigens, Differentiation / Q000032:analysis; D017209:Apoptosis; D018988:Bacterial Translocation; D018797:Cell Cycle Proteins / Q000032:analysis; D004268:DNA-Binding Proteins / Q000032:analysis; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000097:blood; D007421:Intestine, Small / Q000378:metabolism* / Q000473:pathology; D008297:Male; D019879:Paneth Cells / Q000378:metabolism* / Q000473:pathology; D054645:Protein Phosphatase 1; D011518:Proto-Oncogene Proteins / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D000071701:Regulatory Factor X Transcription Factors; D015427:Reperfusion Injury / Q000378:metabolism* / Q000473:pathology; D012771:Shock, Hemorrhagic / Q000473:pathology; D051742:Transcription Factor CHOP / Q000032:analysis; D014157:Transcription Factors / Q000032:analysis; D014409:Tumor Necrosis Factor-alpha / Q000097:blood; D056811:Unfolded Protein Response; D015854:Up-Regulation; D000071717:X-Box Binding Protein 1
D000943:Antigens, Differentiation; D018797:Cell Cycle Proteins; C497249:DDIT3 protein, human; D004268:DNA-Binding Proteins; C497251:Ddit3 protein, rat; D015850:Interleukin-6; C489287:Ppp1r15a protein, rat; D011518:Proto-Oncogene Proteins; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; C000605545:Xbp1 protein, rat; D051742:Transcription Factor CHOP; C087519:PPP1R15A protein, human; D054645:Protein Phosphatase 1